Conservation – Page 28 – Shark Research & Conservation Program (SRC)

Fishermen Views on Marine Protected Areas

December 30, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Alice Schreiber, RJD Intern

As fish stocks continue to decline, Marine Protected Areas are becoming increasingly popular methods of conserving marine habitats and preserving species. The success of these areas depends upon the existing legal framework, acceptance by the community, and an effective management system [1].

Being aware of how fishermen socially perceive MPAs is crucial when establishing them and creating management guidelines. MPAs are established areas where fishing pressure is reduced by designating the amount of fishing effort, time available for fishing activity, species that can be caught, gear permitted, or catch limits [2]. At times, Marine Protected Areas may completely restrict fishing or some areas may be designated Marine Reserves which function as no-take zones. The expectation is that the MPA will “maintain or restore marine biodiversity and ecosystem function,” as well as “improve socioeconomic conditions by increasing revenues from fisheries production due to an increase in the size and number of fish migrating out of the MPA [3]”. Without taking into account the stakeholders’ perception of the reserve, enforcing management of Marine Protected Areas would be nearly impossible.

A new study by Monalisa Silva and Priscila Lopez, sheds some light on how to determine fishermen’s perceptions of MPAs and what criteria influence the opinions the fishermen have about the MPA. When evaluating perception among fishers, four questions are asked: (1) if a fisherman born in a place subjected to the limitations of an MPA has a more conservationist attitude; (2) if young, part-time, non-selective fishers are more flexible and adaptable to changes in the reserves, (3) if full-time fishermen who were born in a community under the influence of an MPA have greater participation in the establishment of management; and (4) if fishermen born in a community under the influence of an MPA have more positive opinions than immigrant fishermen regarding the protected areas [2].

Asking these questions allows researchers and policy makers to understand which individuals within a community are less likely to comply with the regulations, and as such, which individuals would benefit from more education or incentives regarding the protected areas. Compliance will not be at adequate levels if there is not a proper understanding from the public of why MPAs are needed.

Three MPAs in the states of Rio Grande do Norte served as the location for the study, in which one hundred fishermen were interviewed. The fishermen were between the ages of 21 and 77 years old and had an average fishing experience of 29 years. They were split into four groups, depending on their age, birthplace, type of fishing gear, and their level of dependence on fishing. They then took a questionnaire, which assessed their perception of biodiversity conservation, flexibility and adaptability, participation in management, and opinions about MPAs.

The results of this study were able to confirm that older fishermen using selective gear have a more conservationist perception, full-time fishermen who use selective gear have lower flexibility and adaptability, and older fishermen tend to have more positive opinions regarding the MPA [2]. Flexibility and adaptability are important in regards to MPA compliance. Selective fishing gear allows fishermen to target a specific species or size of fish and when that fish stock collapses or is not longer allowed to be fished, they have very little flexibility in their choices. Encouraging fishermen to work in other areas part-time or to explore different resources beyond fish may help to ease the lack of flexibility.

Taking into account stakeholder perception is extremely important for the proper and effective management of MPAs. Compliance issues result from misconceptions of the conservational goals and from heavy dependence on fishing as their primary or only income. Being considerate of these issues allows for more effective management of MPAs and a more positive perception from fishermen and the affected community.

Works Cited

Salm, Rodney V., John R. Clark, and Erkki Siirila. Marine and coastal protected areas: a guide for planners and managers. IUCN, 2000.

Silva, Monalisa RO, and Prisicla FM Lopes. “Each fisherman is different: Taking the environmental perception of small-scale fishermen into account to manage marine protected areas.” Marine Policy 51 (2015): 347-355.

Pomeroy, Robert S., et al. “How is your MPA doing? A methodology for evaluating the management effectiveness of marine protected areas.” Ocean & Coastal Management 48.7 (2005): 485-502.

Commercial Shrimp Trawling: the profit does not out weigh the damaging effects on rest of the ecosystem

December 19, 2014/3 Comments/in Conservation, Ocean News /by aanstett

By Laurel Zaima, RJD Intern

ABSTRACT

Commercial shrimp fisheries’ main objective is to maximize their target catch in order to make the most profit. Commercial shrimp fisheries satisfy this goal by the utilization of trawl nets. Trawling is a very destructive form of fishing, and unfortunately, does not take into consideration ecological consequences. Trawling, by the use of beam or otter trawls, is used to maximize their catch of shrimp; however, it also maximizes their landings of by-catch. The amount of by-catch far out weighs the amount of shrimp and target species caught in trawls. The majority of by-catch, which comprise of non-commercial fish, juveniles, and benthic debris, are landed and discarded back into the ocean dead. The dumping of by-catch then contaminates the water and contributes to the death of other species living in the area. As the weighted trawl nets are dragged across the ocean floor, the benthic habitat is destroyed and collected by the net. Trawling destroys complex habitat structures and seagrass beds, and changes the biochemical composition of the sediment. The alterations to the substrate and damages to habitat configuration can induce an ecological shift of the organisms that live in that area. Invertebrates are especially sensitive to the change of the benthic habitat, and therefore, are indirectly affected by trawling. The invertebrate communities are also directly affected by trawling due to disturbance or mortality. Trawling can inhibit the growth of fish to their natural size as well. Trawl nets catch some species of fish so frequently they are unable to grow into adulthood before they are caught, which leads to truncated size distributions of those species. Trawl nets are also responsible for a shift in organisms of a site and trophic cascades, and cause an imbalance in the ecosystem. The studies conducted about trawls provides a plethora of evidence that confirm commercial trawl shrimp fisheries are unsustainable and cause detrimental harm to the ecosystem.

KEYWORDS

Commercial Fishery

Trawls

By-catch

Catch per Unit Effort

Ecosystem

INTRODUCTION

People all around the world love to eat shrimp and it serves as a staple in many cultural dishes. The high global demand for shrimp makes marine shrimp fisheries a very profitable and competitive market. The majority of all marine fisheries prioritize maximum profit by exploiting their target catch per unit effort. This drives competing shrimp fisheries to a variety of methods to outcompete each other. Commercial fisheries increase the amount of fishing effort by increasing their number of fishing vessels or by extending the duration of their fishing trips. There is advancement on fishing techniques and equipment to exploit the behavior and habitat preferences of target species. The greed of marine fisheries often leads to unsustainable fishing practices, a severe depletion of the target species, pollution and destruction of the marine habitat, and a negative effect on the ecosystem. In the case of shrimp fisheries, they maximize their catch per unit effort by using commercial fishing gear called a trawl. Trawling involves pulling a weighted, sock shaped net through a water column or on the sea floor in order to exploit the catch of a target species. Most commercial shrimp fisheries use beam trawls because they are specifically designed to target benthic species, like shrimp, that either bury or rest on the benthic sediment (Jennings and Kaiser, 1998). Beam trawls are comprised of a rigid beam held off the seabed by two beam shoes; the net headline is fixed at an open position and attached to the beam; the footrope is attached to the beam shoes (Jennings and Kaiser, 1998).

Beam trawl design.

Tickler chains are gear used with trawls because they are designed to penetrate the upper layers of the sediment in order to disturb the target species that are buried in the sediment (Jennings and Kaiser, 1998). The disturbance then forces the target species to swim up and into the path of the trawl. The other kind of trawl is called otter trawls. Otter trawls are comprised of two rectangular otter boards or doors, attached to the towing warps, which keep the mouth of the net open (Jennings and Kaiser, 1998). The heavy weight of the boards can penetrate the soft sediment up to 15 centimeters (Krost et al. 1990). Otter trawls also utilize invasive tickler chains that are attached between the otter boards (Harden-Jones and Scholes, 1974), or damaging rockhopper gear, a type of ground fishing gear that is hopped over rocky substrata (Jennings and Kaiser, 1998). Unfortunately, both categories of trawls are designed to prioritize maximum catch of anything in its path and do not consider the destructive effects it has on the ecosystem. Therefore, trawling is considered the world’s number one marine ecosystem damaging agent. Commercially fishing for shrimp with trawls is an unsustainable fishing practice and causes detrimental harm to the ecosystem.

BY-CATCH

Trawl inefficiency: amount of by-catch vs. target species

Trawls are one of the most unsustainable methods of fishing because trawls catch an outrageously high amount of by-catch in comparison to the amount of target shrimp or commercially profitable fish. Trawls run through the water column or on the sea floor and collect everything in its path, and the majority of organisms caught in trawls are useless by-catch. By-catch refers to marine species or organisms that are unintentionally caught while fishing for a target species. By-catch does not necessarily refer to the death of the inadvertently caught organisms; however, the by-catch of commercial fisheries often dies before it can be released back into the ocean. Fulanda (2003) determined that shrimp trawling in Ungwana Bay was a threat to marine resources due to trawls’ inefficiency. During a survey spanning for a total of 296 trawling hours for a seven-day period on three shrimp fishery vessels, shrimp only constituted of 13.7% of the total catch and 14.4% was commercially profitable fish of the total catch (Fulanda, 2003). This equates less than a third (28.1%) profitability of all the organisms caught within the trawl net. The rest of the catch within the trawl net (79.1%) is all by-catch that is often times discarded back into the ocean dead because these organisms are either non-commercial fish, juveniles, or benthic debris. The majority of the by-catch was due to non-commercial fish, such as Branchyura (crabs), leiognathidae (ponyfish), Apogonidae and Squillidae (Fulanda, 2003). The juveniles caught as by-catch were mostly undersized commercial fish (Fulanda, 2003). The high inefficiency of trawl nets is a serious threat to the future of the commercial fisheries. The commercial fisheries’ actions have a negative feedback on themselves, and if they continue to deplete their own resource, the fishery will not survive. Fortunately, there are some simple solutions to reduce the amount of by-catch caught by trawl nets. The high quantities of juveniles caught as by-catch could be easily avoided by decreasing the mesh size of the trawl nets and by avoiding trawling in shallow areas where juveniles primarily reside (Fulanda, 2003).

By-catch mortality rates

The by-catch organisms of commercial fisheries have varying mortality rates depending on the stress tolerance of the species. Meyer et al. (1999) found that mojarra were highly susceptible to mortality from the trawl nets and the mojarra encompassed 60% of the total catch in August (Meyer et al., 1999). This indicates that over 50% of the trawls’ catch possibly died as by-catch. The differing species mortality from trawling may have an influence on the species diversity and composition of that area with long term trawling (Meyer et al., 1999). The mortality rate of species exposed to trawl nets was also seen to have an inverse relationship with size. Fritz and Johnson (1987) found that a potential explanation for the differences in trawl mortality rate between small and large sized fish could be attributed to larger fish having a greater proportion of muscle tissue and larger energy stores than smaller fish; larger fish with these characteristics are able to avoid net contact during prolonged trawl tows. Therefore, littler, less strong fish are left susceptible to higher rates of stress and mortality from trawl nets. High mortality rates of small fish from trawl by-catch can have a cascading effect on the commercial fisheries. High mortality of small fish depletes an essential food source for juveniles and can reduce the stock of juvenile fish (Meyer et al., 1999). The decline of juveniles can reduce the reproductive potential of a target species and prevent that species from replenishing their stock. This, in turn, can hurt a commercial fishery because their target species’ stock is being exhausted.

By-catch dumping

Harris and Poiner (1990) assessed the quantity and composition of by-catch from commercial prawn trawling in Torres Strait, Australia over a 2-year period. They found that a wide range of marine organisms were caught as by-catch including cephalopods, crabs, rock lobsters, scallops, sharks, rays, snakes, turtles, and mostly teleost fish (Harris and Poiner, 1990). Apart from the small amount lobsters and squid, nearly all the by-catch (approximately 99%) was discarded dead (Harris and Poiner, 1990). Majority of the time, the by-catch, whether dead or alive, is dumped back into the ocean. The large amount of dead by-catch pollutes and contaminates the water, which can result in more organismal death in that area. Fulanda’s (2003) study also found that by-catch dumped back into the waters is an environmental and health hazard because of fouling and contamination of the waters and fish harvested by artisanal fishermen. This study found that a better use of by-catch is to “off-load” it to the artisanal fishing boats that have very low catches due to their low levels of fishing technology (Fulanda, 2003).

By-catch of infaunal species and effects

A study conducted by Jennings and Kaiser (1998) found that a trawl net’s by-catch of non-target infaunal species have drastically affected the benthic communities. Their study found that the by-catch of the infaunal bivalve, Arctica islandica, and the heart urchin, Echinocardium cordatum, by a beam trawl indicates that the tickler chains penetrated hard sandy substrate to at least a depth of 6 cm where these organisms primarily reside (Jennings and Kaiser, 1998). The invasive nature of trawls not only collects these benthic species as by-catch, but it also destroys the benthic habitat.

DESTRUCTION OF BENTHIC HABITAT

Trawling effects on different bottom types

Trawls have been designed to maximize their contact with the seabed in order to attempt to catch most amount of shrimp, however, this method demolishes the benthic habitat. The different types of bottom habitats have varying resilience to trawling. In order to understand how different bottom types respond to shrimp trawl fishing, Wells et al. (2008) conducted a study to identify the differences in community structure among sand, shell, and reef habitats in trawled and non-trawled areas in the Gulf of Mexico. They found differences in the habitat characteristics, and therefore, differences in the biotic community structure between trawled and non-trawled areas, which suggest that trawling may impact the benthic ecosystem (Wells et al., 2008). The patterns they observed from trawl fishing specifically indicated that more complex habitats, such as complex shell-rubble habitats, are more sensitive to the effects of fishing activities like trawling (Wells et al., 2008).

A. The coral community and seabed on an untrawled seamount; B. The exposed bedrock of a trawled seamount.

The destruction of complex habitats consequently reduces the amount of refuge for resident species, and can further result in a loss of species diversity and/or abundance of that trawled area.

Trawling varying effects of mud-bottom substrata

Multiple studies have indicated that the consequences of trawling are most apparent in relatively high relief, complex areas of seabed such as boulders, gravel, and rippled sand bottoms (Auster and Langton, 1999; Wells et al., 2008). However, trawling effects are still evident on mud substrate, and it can affect small-scale physical, chemical and biological habitats (Simpson and Watling 2006). Trawling on a mud-bottom habitat also may reduce the habitat structure by the removal or the death of the sediment dwelling organisms that increase the physical heterogeneity in soft sediments by burrowing and feeding (Simpson and Watling, 2006). Simpson and Watling (2006) further investigated the impacts of shrimp trawling on the mud-bottom habitat. They assessed the effects of trawl induced sediment disturbances on the habitat structure by the burrow density and the sediment porosity. Burrows increase the sediment surface area exposed to the overlying water column, are areas of chemical reactions with oxygen, dissolved metals and other elements in solution, and are sites of enhanced diagenesis and nutrient cycling (Aller, 1982). The reduction in burrow densities due to trawling is expected to impact the localized sediment elemental cycling and organic matter (Aller, 1994; Aller, 1982). Sediment porosity is and indicator of sediment grain size, arrangement, and the capability of the sediment to support animals (Simpson and Watling, 2006). Simpson and Watling (2006) found that trawling indeed had changed the porosity and sediment grain size to an extent, but it did not have a significant change to the porosity of the fishing grounds. In terms of burrow density, they found that the burrowing density was more abundant in trawled areas, which indicates that mud-bottom fishery grounds have a high recovery recolonization (Simpson and Watling, 2006). They concluded that in this area mud-bottom habitat could with stand trawl fishery efforts without a lasting impact on the overall habitat. However, Smith et al. (2000) also examined the effects of commercial trawl fisheries on a mud-bottom habitat in the eastern Mediterranean Sea and his study showed differing results. He found that there was a strong negative impact of trawling on the benthic macrofauna and megafauna, and a significant change in the sedimentary organic carbon, chlorophyll, and phaeopigments in trawled areas (Smith et al., 2000). The differences between the results of these two studies indicate that trawling has variable effects depending on the area being trawled and the bottom type of that area. Therefore, trawl-fishing grounds should be tested for resilience to trawl disturbance prior to committing a site to long term trawling.

Trawl destruction of seagrass beds

Shrimp trawling fisheries that profit off of the catch of live-bait shrimp target different fishing areas of high productivity. A live-bait shrimp trawl fisheries primarily target pink shrimp, Penaeus duorarum. These pink shrimp reside in beds of highly productive turtlegrass, Thalassia testudinum, therefore, live-bait shrimp fisheries run their trawls through these vital ecosystems in a quest for maximum catch per unit effort (Tabb and Kenny, 1969). Trawls have not been known to up root the seagrass beds because turtlegrass has an extensive root system; however, these trawls will damage and break off the turtlegrass leaves and collect them in the trawl net (Woodburn et al., 1957). The demolition of seagrass beds by trawls has the potential to change the composition of the local ecosystem by destroying a key habitat for many local species. Additionally, the trawl nets have a tendency to collect and redistribute the macroalgae and turtlegrass litter throughout different regions of the sea floor (Meyer et al., 1999). This redistribution can significantly reduce the habitat complexity of one area and enhance the complexity of another, which will make the benthic habitat unbalanced (Meyer et al., 1999). Consequently, altering the habitat can have a direct effect on the composition and abundance of the species that reside in that area.

Effects of resuspension of sediment due to trawling

Many benthic environments have a significant nepheloid layer, characterized as a near-bottom region of permanent sediment suspension (Pilskaln et al., 1998). High frequency commercial trawling may have significant effects on the resuspension fluxes of sediment and it may contribute to the maintenance of the nepheloid layer. Pilskaln et al. (1998) wanted to specifically see if the trawling in the Gulf of Mexico, where there is a thick and basin-wide nepheloid layer, increases the resuspension layer and the effects it has on the ecosystem. They observed the nepheloid layer after trawling disturbances of the infaunal organisms that characteristically live in the sediment. Polychaete worms are benthic, infaunal worms that do no swim far above the sediment water interface; however, polychaetes were found caught within the sediment traps deployed in various locations in the Gulf of Mexico (Pilskaln et al., 1998). These results suggest that the trawling fishing gear may be responsible for the artificial resuspension of the bottom sediments, and there by, either resuspending the worms from the sea floor into the nepheloid layer or discharging the worms from the net and bringing them to the surface near the trap site (Pilskaln et al., 1998). The resuspension of the sediments by trawling directly disturbs the polychaete worms from their natural habitat and it also has biogeochemical consequences. The majority of the nutrients in the continental shelf are from primary production from the sediment, which is derived from organic matter decay and nutrient remineralization (Pilskaln et al., 1998). Trawling effects the sediment nutrient fluxes in several ways. Trawling can bury the fresh, organic matter into subsurface horizons from its normal position at the sediment-water interface, which will shift organic matter decay from aerobic, eukaryotic populations towards anaerobic, prokaryotic metabolism (Mayer et al., 1991). Trawling can also physically enhance the upward flux of remineralized nutrients in the interstitial pore water of the sediment, which will result in the nutrients entering the water column in a large pulse rather than by the usual slower and steady mechanisms (Pilskaln et al., 1998). The abundance of nutrients at one time can have alterations in the rate and type of primary production (Pilskaln et al., 1998). These biogeochemical modifications to the sediment from trawling resuspension can have a cascade effect and also change the species composition of the area. Trawling changes an area chemically, physically, and biologically and these changes have corresponding effects on the organisms that reside in these areas.

ALTERATIONS IN THE INVERTEBRATE COMMUNITY

Invertebrate species response to direct trawling

Since trawls have significant effects on the benthic habitat, consequently, trawling alters the abundance and diversity of the benthic community.

Trawling an area can either directly affect the infaunal, invertebrate community by mortality and/or disturbance, or trawling can indirectly affect invertebrates by the destruction of their habitat and/or chemical changes to the sediment. Simpson and Watling (2006) found that there are clear disturbances in the macrofaunal community structure in areas of recently shrimp-trawled areas, where as, there was no detection of disturbance in areas of older (minimum of a year prior) trawling activity. Specifically, trawling-sensitive taxa, like bivalve families Nuculidae and Nuculanidae, were more abundant in untrawled areas because these species could not tolerate the damaging effects of trawls (Simpson and Watling, 2006). Many studies, including Simpson and Watling (2006), have observed trawling affecting invertebrate species differently depending on their life histories. Invertebrate species of large, long-lived animals living near the surface of the sediment are predicted to be more sensitive to trawling disturbance, where as, small, fast growing, regenerating and mobile animals are expected to be more dominant in trawled areas (De Groot, 1984; Rumohr and Krost, 1991; Hall, 1994; Kaiser 1998; Thrush et al., 1998). Unfortunately, this sensitivity corresponds to their mortality rate to trawls as well. The mortality rates of infaunal organisms due to trawling depend on certain life history characteristics, such as body size and depth distribution within the sediment (Duplisea et al., 2002). Fortunately, the macrofaunal communities on mud-bottom trawling grounds have fast recovery rates due to their high reproductive output (Simpson and Watling, 2006). The invertebrates of mud-bottom trawling sites, in comparison to more sensitive species in other habitats, are capable of withstanding the consequences of trawling if there is an adequate amount of time given for recovery between trawls. However, over harvesting or long-term trawling of a centralized location, even a tolerant habitat like a mud-bottom, could result in a semi-permanent degradation of the invertebrate abundance and diversity (Jones, 1992; Auster et al., 1996, Gray, 1997, Jennings and Kaiser, 1998).

Hansson et al. (2000) sought to study the effects of trawling on assemblages of macro fauna in Gullmarsfijorden, Sweden. The study found that there was an overall appearance of a negative trend in abundance of macrofauna within the fjord. Explicitly, the negative effects of trawling declined the abundance of echinoderms, especially the ophiurids (brittle starts) (Hansson et al., 2000). Hansson et al. (2000) found that the ophiurids’ population decreased by an average of 30% at trawled sites in comparison to the untrawled sites. These results are somewhat surprising because ophiuroids have the ability to regenerate lost body parts and it would have been assumed that they would be resistant to trawling (Lindley et al., 1995; Kaiser and Spencer, 1996; Tuck et al., 1998). There is a possibility that the decline in abundance of ophiuroids is due to responses to oxygen stress (Hansson et al., 2000). Ophiuroids may have migrated from protected sediment to a more exposed position on the sediment surface as a response to sub-lethal hypoxia (Rosenberg et al., 1991) induced by the absence of water renewal in the deep parts of the fjord in 1997 (Hansson et al., 2000). Once the Ophiuroids were exposed to the surface of the sediment, they were also exposed to the shrimp trawl nets that either directly destroyed their bodies beyond regeneration or caught them as by-catch.

Invertebrate species response to indirect trawling

Some Invertebrate species are sensitive to alterations in their environment and can be indirectly affected by trawling that destroys their habitat. In looking at the invertebrate community structure after trawling, Wells et al. (2008) study indicated that some invertebrate species such as two brittle stars (O. appressum and O. elegans), a sea star (L. clathrata), and urchin (A. punctulata), a hairy sponge crab (D. antillensis), the shortfinger neck crab (P. sidneyi), and brown rock shrimp (Sicyonia brevirostris) are more abundance in structurally complex, non-trawled areas. Essential complex habitats provides shelter and protection for these invertebrates, and without these structures, these invertebrates are vulnerable and susceptible to predation. Therefore, these species are more sensitive to trawling because it destroys their complex habitats necessary for their survival. The shrimp trawling has variable direct and indirect effects on the invertebrate community depending on the species and the bottom type sediment of a fishing ground; however, the negative impacts of trawling can create a bottom up cascade from the invertebrates to other species of the ecosystem.

DISTRUPTIONS IN THE FOOD WEB AND ECOSYSTEM

Trawls destruction of habitats drive an ecosystem shift

The food web and ecosystem are severely disrupted by the destructive method of trawling and the shrimp commercial fisheries’ high consumption of target species and by-catch. The loss in the structural benthic habitat can result in a shift of residing marine organisms. Wells et al. (2008) found that with the loss of the structural epibenthic community due to trawling resulted in a shift from snappers (Lutjanidae) and emperors (Lethrinidae) towards an ecosystem dominated by lizardfish (Synodontidae) and bream (Nemipteridae). In general, trawled areas become inhabited by species with similar life characteristics, including: small size, short life spans, high mortality, and rapid biomass turnover (DeVries and Chittenden, 1982; Geoghegan and Chittenden, 1982; Murphy and Chittenden, 1991; McEachran and Fechhelm, 1998). Species including the longspine porgy, silver seatrout, large-scale lizardfish, and gulf butterfish are all species that successfully inhabit trawled areas because their life history characteristics will allow them to recover swiftly after the damage (Wells, Cowan, and Patterson, 2008). The destruction to habitats caused by trawls has an influence on the entire ecosystem composition and potentially reduces species diversity.

Trawling triggers truncated size distributions

Some fish species in trawling areas have been seen to have truncated size distributions and reduced median size. In the Gulf of Mexico, the species that showed truncated size distributions over trawled areas were the same species that were the most abundant caught as by-catch in the shrimp trawl fishery (Wells et al., 2008; Chittenden and McEachran, 1976). Similarly, other studies have found that trawling and dredging is the cause of a decrease in biomass and average size of demersal fish and invertebrate fauna (Bianchi et al., 2000; Zwanenburg, 2000, Duplisea et al., 2002). The observations of truncated size distributions of local fish indicates that a species is caught at such a high frequency that they are unable to grow into adulthood before they are caught and captured. This can severely affect the population, abundance, and health of a species.

Manipulation of the ecosystem into a top-down trophic cascade

Trawling also has the ability to manipulate the ecosystem in ways to actually produce more target shrimp by reducing the amount of predators. Salcido-Guevara et al. (2012) discovered that shrimp trawling in La Paz Bay had positive impacts on the shrimp populations because the by-catch from the trawl nets actually reduced the amount of shrimp predators. This study suggested that predator removal had a strong positive impact on the shrimp’s population than does the negative impact of fishing the shrimp (Salcido-Guevara et al., 2012). These results are alarming because the human manipulation of an ecosystem does not always end with the results that are desired or expected. By purposefully decreasing the amount of shrimp predators for their benefit, the fisheries are creating a top-down trophic cascade. A top-down trophic cascade suggests that the apex predators’ populations have the power to alter the rest of the food web; for example, if there is a reduction or depletion of predators, there will be a rise in prey’s population. This trophic cascade continues down the food web and will eventually either deplete or alter the diversity of the primary producers. Trophic cascades can throw the ecosystem food web out of balance, causing expansive negative effects that were not initially considered. Nonetheless, under heavy shrimp fishing pressure, both shrimp and the predator’s biomasses will sharply decline as expected (Salcido-Guevara et al., 2012).

DISCUSSION

Shrimp fisheries current trawling methods can have extensive negative impacts on the habitat structure, the benthic invertebrate community, the shrimp population, other local species abundance and diversity, and the overall balance of the ecosystem. The shrimp catch of the commercial trawl fisheries do not out weigh the externality that trawls exert on the ecosystem. With long term and frequent trawling of an area, eventually, benthic habitat will be destroyed, the species diversity and abundance will decrease, and in turn, the target species will also decline. Therefore, there is a negative feedback on the shrimp fishery when utilizing the current design of trawls in high frequency. The implications of these findings confirm that changes need to be made before the destruction of trawling is irreversible. There are some potential solutions to reduce the damaging impacts of trawling. The avoidance trawls is the most effective way to prevent damage; therefore, educating people about the unsustainability of commercial shrimp fisheries and encouraging people to reduce their intake of shrimp can have a large impact on the reduction of damage by trawling. If there is a decline in the demand of shrimp, then the shrimp fisheries will reduce their trawling efforts. Another potential solution is providing alternatives to trawling. Although it’s a less practical solution, self-catching shrimp with a net is encouraged because it is the least invasive to the environment. By employing shrimp catching as a sport or as an ecotourism attraction, people can catch their own dinner and have fun doing it. However, the problem with this is that most people do not live in an area where they can catch their own shrimp so readily.

Commercial shrimp fisheries can also implement their own modifications to their current trawling methods in order to help reduce damage. By limiting the amount of time per trawl tow and the trawl frequency of an area, the bottom habitat and local organisms will be given a chance to recover. Trawling time constraints will prevent a site from being over exploited beyond recovery. Shrimp trawls can also reduce negative impact by modifying the area and the depth at which they tow. Shrimp trawling is seen to have the least destructive effects on certain mud-bottom substrata (Simpson and Watling, 2006). Damage to complex structures and essential habitats can be avoided if commercial shrimp fisheries localized their trawling to a more stress tolerant area, such as mud-bottom habitats. Fulanda (2003) found that trawling in shallow areas increases their by-catch of juveniles. Therefore, regulations set for a minimum trawl depth will prevent trawls from being towed in too shallow areas where juveniles primarily reside. Modifications to the net design can further improve the reduction of by-catch. Decreasing the mesh of the trawl net can reduce the amount of small fish by-catch and juvenile by-catch (Fulanda, 2003). There are a variety of potential solutions to the damaging effects of trawl nets, but first, the attitude of the commercial shrimp fisheries need to change. Commercial shrimp fisheries need to stop prioritizing their maximum profit for “right now,” and instead, start considering the effects their fishing practices have on the ecosystem and the future of their fishery. With a changed mindset, initiatives for sustainable fishing will be prioritized and shrimp fishing will pose less damaging consequences on the ecosystem.

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71 Questions: A Guide for Marine Conservation

December 16, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By James Keegan, RJD Intern

The ocean remains an immense resource for humanity, providing food, economic activity, and cultural roots for many. Although these resources are valuable, it is difficult to effectively protect them because our knowledge of marine ecosystems is lacking. To correct this insufficient understanding of the marine environment, Parsons et al. 2014 conducted two workshops in order to establish a list of important questions that would help direct conservation research. If conservationists can answer these questions, the community’s ability to conserve and mange the world’s marine resources would substantially improve. With the contributions from participants in the fields of science, conservation, industry, and government, Parsons et al. 2014 identified 71 key questions for the preservation of the marine environment. They then grouped these questions into 8 categories, each associated with an aspect of marine conservation: fisheries, climate change, other anthropogenic (human caused) threats, ecosystems, marine citizenship, policy, societal and cultural considerations, and scientific enterprise. Using these questions as guidelines, funders and researchers can develop programs that can greatly benefit marine conservation.

Because oceans are vast, and their environments difficult to access, marine research is expensive and difficult to undertake. Expensive technologies necessary for accessing marine environments, like submersibles, raise costs beyond those typically incurred by terrestrial, or land-based, studies. Moreover, marine conservation research receives funding at a much lower rate than terrestrial conservation. In order to combat these issues, Parsons et al. 2014 sought out to identify a set of questions that, if answered, would contribute immensely to conserving marine ecosystems on a global scale, thus maximizing the returns of the research programs involved. By prioritizing the most important questions facing marine conservation, conservationists can more effectively protect the marine environment with the funding they receive.

A table showing example questions produced by Parsons et al. 2014 for each of the 8 categories.

In order to produce their list of key questions, Parsons et al. 2014 conducted a pair of workshops. In their first workshop, held during the second International Marine Conservation Congress (IMCC), 17 participants with varying expertise reviewed an initial list of 631 questions. Parsons et al. 2014 solicited these initial questions from participants at IMCC, professional peer groups, and the Society for Conservation Biology. The 17 participants reduced the number of questions to 316, and Parsons et al. 2014 voted on these remaining questions in their second workshop, ultimately reducing the number to 71. Finally, they grouped these 71 questions into 8 categories: fisheries, climate change, other human produced threats, ecosystems, marine citizenship, policy, societal and cultural considerations, and scientific enterprise.

A flow chart summarizing the steps taken in the workshops. (Parsons et al. 2014)

Each of the 8 categories pose challenges to marine conservationists. Mass extraction of fish and other organisms stress marine ecosystems and can lead to overexploitation. Components of climate change, like warmer waters and ocean acidification, directly affect marine species and indirectly affect ecological interactions. Other human activities negatively impact marine ecosystems, like fertilizer runoff creating oxygen-depleted areas in the ocean, or global shipping routes introducing invasive species into new areas. Because conducting research in the marine environment can be difficult, marine ecosystem processes and population dynamics are poorly understood. The behavior and lifestyle choices of individual citizen’s significantly impact the health of the marine environment, but the best methods for engaging the public and promoting marine conservation remain illusive. Marine conservation and resource use policy are challenging because marine policy encompasses both the lack of information on marine systems and complex governance issues. Moreover, marine conservation is closely tied with socioeconomic and cultural factors, requiring engagement in such areas with targeted research. Scientific culture itself needs reworking, in that data sharing, collaboration, and funding for fields like taxonomy need to improve. With so many issues facing marine conservation, the questions articulated by Parsons et al. 2014 will help focus the conservation effort.

Past ecological prioritization exercises underemphasized marine issues, so Parsons et al. 2014 highlighted the specific challenges facing marine conservation. Although these questions have not been answered completely, people can, and should, undertake reasonable conservation efforts regarding their subject matter. By serving as a guide for scientific research, these 71 questions, along with evidence-based, participatory, and transparent management, can lead us towards effective marine conservation.

References:

Parsons, E. C. M., Favaro, B., Aguirre, A. A., Bauer, A. L., Blight, L. K., Cigliano, J. A., Coleman, M. A., Côté, I. M., Draheim, M., Fletcher, S., Foley, M. M., Jefferson, R., Jones, M. C., Kelaher, B. P., Lundquist, C. J., McCarthy, J.-B., Nelson, A., Patterson, K., Walsh, L., Wright, A. J. and Sutherland, W. J. (2014), Seventy-One Important Questions for the Conservation of Marine Biodiversity. Conservation Biology, 28: 1206–1214. doi: 10.1111/cobi.12303

Five Ways to Fight Illegal Fishing

November 24, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Lindsay Jennings, RJD Intern

The issue of illegal fishing has, deservedly, been getting international attention recently but it should be noted that this ‘great ocean heist’ is not a new phenomenon. For far too long fishing boats have been misreporting or underreporting their catches. There simply are not enough fish for these boats to catch so they resort to illegal, unreported and unregulated (IUU) fishing. IUU fishing accounts for $10-$23 billion annually in internationally traded seafood,[1] and to compound the problem, it has been linked to environmental degradation, political instability, slave labor, and the movement of other illicit cargo like drugs and weapons. While there is not one single solution, there can be a complimenting set of actions taken at international, national, and local levels to address this threat, of which the top five are presented below:

Legislation – It is crucial to develop the framework for addressing IUU fishing on a global scale, as this kind of fishing is rarely confined by species or geographic boundaries. Legislation like the Port States Measures Agreement (PSMA) gives countries the opportunity to reduce profitability of IUU fishing by denying port access and services to IUU vessels, better controlling what seafood is coming into their ports.[2] Combined international efforts to pass and implement this global treaty would allow some of the world’s largest and most lucrative ports to not only penalize those who illegally fish but close the market for vessels trying to offload their catch.

Global Vessel Identification – Although the right to fish on the high seas is given to all countries, some are unwilling or unable to enforce their regulations, providing illegal fishermen with ‘flags of convenience.’ When IUU vessels are compromised, crews will often re-flag, or re-register, their vessels to a different port state, evading law enforcement and circumventing international fishing regulations.[3] Similar to a car’s Vehicle Identification Number (VIN) or our Social Security Numbers, Unique Vessel Identifiers (UVI) can be used to ‘tag’ a fishing vessel with a non-transferable, unique number which stays with that vessel until it is permanently taken out of the water. By eliminating the ability for vessels to hide behind a new identity, punishments for illegal fishing activities would dramatically increase.³

Unique and permanent vessel identification numbers can help cut down IUU vessels from re-flagging themselves. Credit: Wikimedia Commons

Seafood Traceability – The United States is the second largest importer of seafood,[4] a commodity which earns more in annual trading than coffee, cocoa, bananas, and rubber combined. With the majority of seafood caught out of sight of authorities, it is essential to ensure that what is being caught and sold is done so legally. Traceability programs would require imports to be accompanied with documentation describing vessel, date, location, gear, species, and common name, to ensure traceability from bait to plate.[5] Seafood retailers have the ability to influence consumer behaviors and demand for legal seafood. They can shift the risk to reward ratio of IUU fishing by eliminating market access for illegal seafood, stopping it from ‘paying off.’[6]

Monitoring, Surveillance, and Compliance (MSC) – While legislation and regulations offer a sound framework, they become ineffective if vessels are not complying with those regulations.[7] Enforcement is often lacking or nonexistent on the high seas, therefore MSC systems must be implemented to ensure adequate monitoring and surveillance. The simple use of technology like vessel monitoring systems (VMS) and automatic identification systems (AIS) would guarantee vessels are fishing within legal limits. Beyond VMS and AIS, satellite monitoring and even remote operated drones have proven to be effective,⁶ allowing authorities to watch fishing effort from 1000’s of miles away and adding a much-needed layer of accountability.

Portuguese Navy and Gabonese sailors work together to inspect a holding bay for fish aboard an IUU fishing vessel. Credit: U.S. Navy

Development – IUU fishing often stems from developing country’s underlying social, economic, and political issues, meaning they have greater difficulties achieving enforcement and compliance.⁷ With the primary motivation for IUU fishing being financial gain, coupled with poor economic prospects, incentive will remain to engage in this kind of fishing until alternative jobs pay a higher wage.³^,⁷ Governments and non-governmental organizations should cooperate to develop alternative sources of employment to disincentivize IUU fishing without sacrificing the ability of those fishers to support themselves.

The Coast Guard Cutter, Rush, escorts a high seas illegal fishing vessel back to port. Credit: U.S. Coast Guard

IUU fishing is one of the most serious threats facing the achievement of sustainable global fisheries and food security. Fortunately, the tools to fight IUU fishing already exist. The responsibility doesn’t lie with one country, but with a strong and coordinated effort of international and national players who can effectively deter fishers from engaging in and benefitting from IUU fishing.

[1] Agnew, David J., John Pearce, Ganapathiraju Pramod, Tom Peatman, Reg Watson, John R. Beddington, and Tony J. Pitcher. “Estimating the worldwide extent of illegal fishing.” PLoS One 4, no. 2 (2009): e4570.

[2] Flothmann, Stefan, Kristín von Kistowski, Emily Dolan, Elsa Lee, Frank Meere, and Gunnar Album. “Closing loopholes: getting illegal fishing under control.” Science 328, no. 5983 (2010): 1235-1236.

[3] Gallic, Bertrand Le, and Anthony Cox. “An economic analysis of illegal, unreported and unregulated (IUU) fishing: Key drivers and possible solutions.” Marine Policy 30, no. 6 (2006): 689-695.

[4] NOAA. 2012. Fisheries of the United States 2011. National Marine Fisheries Service and the Office of Science and Technology. Available via: http://www.st.nmfs.noaa.gov/st1/fus/fus11/FUS_2011.pdf.

[5] Borit, Melania, and Petter Olsen. “Evaluation framework for regulatory requirements related to data recording and traceability designed to prevent illegal, unreported and unregulated fishing.” Marine Policy 36, no. 1 (2012): 96-102.

[6] Global Ocean Commission. “Illegal, unreported, and unregulated fishing.” (2013). Available via: http://www.globaloceancommission.org/wp-content/uploads/GOC-paper08-IUU-fishing.pdf

[7] Erceg, Diane. “Deterring IUU fishing through state control over nationals.” Marine Policy 30, no. 2 (2006): 173-179.

Watered Down Medicine: The Influence of Marine Organisms in Medicine

November 20, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Gabi Goodrich, RJD Intern

Ancient people worshipped, prayed, and sacrificed to the ocean for the powers of healing and power it possessed. While the mentality has changed, the influence over people and medicine today has not. With more and more focus on disease and sickness, the search for new and better medicines are an exponentially growing field. Over the past 20 years, around 10,000 known natural substances have been found from isolating marine organisms. Only a mere 28 of these are currently in clinical testing, and some are in pretrial. While only a small number of drugs on the market today are actually derived from marine organisms, the appeal of the new source can be found in the differential compounds of marine dwelling organism versus land-dwelling ones. These few organisms that have been approved by the Food and Drug Administration (FDA) do play an everyday role in the medical field and technology. Horseshoe Crabs have been widely used for their blood, which is used to screen intravenous drugs for bacteria contamination. Still, it is important to remember that marine organisms are not just the macrofauna, but also include sponges, cyanobacteria, corals, and algae. For example, the chemicals located in cyanobacteria have been found as an effective malaria treatment. Sponges also appear to be a very promising field. Researchers found that many species of sponges, such as Tethya crypta, show signs of anticancer and antiviral agents. Though, many discoveries have already been made using sponges. The drug Halaven, used for metastatic breast cancer, was originally derived from the Halichondria sponge family. Furthermore, the work with nucleosides in the Caribbean sponge Cryptotethya crypta had set the basis for the synthesis of Ara-C, which created Cytarabine, used to treat cancers of white blood cells, in 1969.

A Caribbean sponge.

It is essential to state that there is a definite paradigm shift in the view of marine organisms as a viable source for new medicines and advances. Scientists are also turning to corals for their naturally occurring source of prostaglandins, which are hormones manufactured in tissues that control activities such as blood clotting and complex inflammatory responses. The trials using prostaglandins are still ongoing. A less common, yet highly used, breakthrough was the use of conotoxins from the venom of marine cone snails. In the natural environment, snails would use this venom to paralyze their prey. In humans, this venoms attack the metabolism at given points. However, a modified mixture of this toxin provides a morphine-alternate and provides a more powerful painkiller than morphine. This discovery came thirty years after the discovery of Ara-C.

A marine cone snail eating.

The most recent contribution from marine organisms to medicine is the advancement of trabectidin, an alkaloid, from Ecteinascidia turbinata, the mangrove tunicate. In 2008 the Food and Drug Administration approved Yondelis, which is used in antitumor treatment and prevents resistance to chemotherapy. The possibilities for the use of marine organisms and the compounds derived from them are endless. However, many obstacles must be overcome in order to even start testing using these compounds.

With so many advancements, the problem does not lie in the potential of the ocean but rather the resources of location and production. 95% of the ocean has yet to be explored. With such a vast expanse to explore, the technology does not yet support the collection and storage of organisms and molecules. It is important to also remember that pharmaceutical companies work for profit. The time and money it takes to locate and test the organisms far out ways the profit that would be made from the potential new drug, which is why the ocean was overlooked for such a long time. With that being said, the advancement of new technology, the time and effort it takes to test has been reduced significantly from the methods of testing in the past. This in turn, takes less money than in previous years. The DNA sequencing of numerous marine organisms make it easier for scientists to have a better idea of which favorable DNA sequences are in which organisms in a short amount of time. Yet another hurdle is how to handle the problem of exploitation. Professor Steve Yearley, head of the ESRC genomics forum, explains while there are controls for regulating the exploitation of animals, plants and microbes on land, regulating them at sea is going to be infinitely more difficult “We cannot stop pirates off Somalia, so how is someone supposed to protect rare sponges that they find in their coastal waters?” Moreover, because many of these organisms are in limited quantity, the susceptibility to changes like temperature, salinity, acidity threatens to destroy them. With the rapidly changing world it is important to protect the oceans and what they could hold.

Works Cited

“Medicines from the Sea.” NOAA. National Oceanic and Atmospheric Administration, n.d. Web. 2 Oct. 2014.<http://www.noaa.gov/features/economic_0309/medicines.html>.

Davis, Alison. “Medicines By Design.” Chapter 3: Drugs From Nature, Then and Now. National Institutes of Health, July 2006. Web. 2 Oct. 2014 <http://publications.nigms.nih.gov/medbydesign/chapter3.html>.

Gerwick, Bill. “Introduction to Drug Discovery From Marine Organisms.” (n.d.): n. pag. Oregon State University. Web. <http://agsci.oregonstate.edu/aquatic-bt/sites/default/files/Gerwick-New_Medicines_from_the_Sea.pdf>.

Fenical, William. “MARINE BIODIVERSITY AND THE MEDICINE CABINET THE STATUS OF NEW DRUGS FROM MARINE ORGANISMS.” 9.1 (1996): n. pag. The Oceanography Society. Web. <http://www.tos.org/oceanography/archive/9-1_fenical.pdf>.

Levins, Nicole. “Coral Reefs and Medicine | The Nature Conservancy.” Coral Reefs and Medicine | The Nature Conservancy. The Nature Conservency, n.d. Web. 2 Oct. 2014. <http://www.nature.org/ourinitiatives/habitats/oceanscoasts/explore/coral-reefs-and-medicine.xml>.

Maxwell, Sara. “Medicines from the Deep: The Important of Protecting the High Seas from Bottom Trawling.” (2005): n. pag. Natural Resource Defense Council, Mar. 2005. Web. <https://www.nrdc.org/water/oceans/medicines/medicines.pdf>.

Effects of Anthropogenic Noise on Marine Mammals

November 17, 2014/1 Comment/in Conservation, Ocean News /by aanstett

By Daniela Escontrela, RJD Intern

A topic of concern in the past few years has been noise pollution in the ocean. Particularly, noise pollution has been thought to affect marine mammal populations since they are so reliant on acoustics for navigation and communication (Erbe 2011). Marine mammals are of special conservation concern because they have been so heavily exploited in the past century via whaling and bycatch (Tyack 2009). The marine mammal protection act was developed 1972 and aimed at protecting and conserving marine mammals and their natural habitats (Tyack et al 2003). However, at the time the marine mammal protection act was passed many of the regulations were based on the pressures of whaling. Now that whaling is better controlled, it is possible that degradation of habitat from multiple sources may pose a bigger threat to marine mammals. One of these impacts that may be causing degradation to marine mammal populations and their environment is noise pollution. (Tyack 2009) The marine soundscape can be complex and for this reason it is hard to study effects of anthropogenic noise on marine mammals. In addition to anthropogenic sounds such as those that come from ships, petroleum exploration and naval sonar, among others, the marine soundscape is also made up of natural ambient sounds such as wind and waves and biological sounds such as calls emitted from marine mammals, fish and crustaceans. (Erbe 2011) This intricate combination of sounds in combination with lack of adequate technology and the difficulty of studying these sometimes elusive animals has made this area of study a hard one.

In 1971 biologist Roger Payne and engineer Douglas Webb were among the first to raise concern over how anthropogenic noise could affect marine mammals. It had been recently discovered that baleen whales used special calls for reproductive purposes. These calls could usually be detected as far away as 280 km away, however, Payne and Webb calculated that with increased ambient noise due to modern commercial ships, these calls were being masked and could only be detected at 90 km distance now. (Tyack 2009) Anthropogenic noise can also mask echolocation clicks which are used by Odontocetes (toothed whales) for finding food and navigation and it can also mask environmental noises that animals listen to such as surf and approaching predators. (Erbe Farmer 2000) If noise masks communication signals, this can disrupt mating systems or parental care and affect reproduction and survival of young in endangered populations. (Tyack 2009) Anthropogenic noises have also been seen to disrupt normal behaviors such as cessation of feeding, resting, socializing and onset of alertness or avoidance. (Erbe Farmer 2000) If foraging is affected by noise this can cause animals to grow more slowly (Tyack 2009). These man made noises can even cause damage to hearing by decreasing auditory sensitivity which can be permanent or temporary. However different animals have different sensitivities and are impacted differently, for example mystecetes (baleen whales) are more sensitive at lower frequencies. (Erbe Farmer 2000)

Early experiments tracked migrating gray whales (mystecetes) as they traveled the corridor of California and found that these whales were sensitive at certain pressure levels when sounds that imitated those from ships or dill rigs were played back to them. Migrating bowhead whales traveling past seismic survey vessels were also studied and found to be sensitive at certain pressure levels. In fact these whales wouldn’t come within 20 km of these areas because the air guns used in these surveys were so intense. It has been shown that many mystecetes show avoidance of certain areas were such loud noises occur. Odontocetes have been harder to study because of their prolonged dives, sometimes exceeding an hour. In the little research that has been done, Odontocetes don’t show the same avoidance of anthropogenic noises that mystecetes show. One study used tagged sperm whales to see how they would respond to the air guns used by seismic survey vessels. The whales were satellite tagged and seismic survey vessels ramped up their air gun array and conducted controlled approaches to tagged whales. None of the seven whales tagged seemed to avoid the vessel. One of the whales remained on the surface and only began a foraging dive after the noise had ceased. The other six whales that were tagged continued their foraging dives. What was found however was that these whales were seen to reduce their swimming effort and they reduced their attempts at catching prey. This suggests not an avoidance pattern like some mystecetes but instead a behavior change, in this case foraging behavior was altered. (Tyack 2009)

An image of the satellite tag used by Tyack fitted onto the back of a sperm whale

Seismic surveys and pile driving can produce some of the most intense anthropogenic noises in the marine environment. How these activities affect marine species depends on how well the sound propagates underwater, its frequency characteristics and its duration. In a study by Bailey et al 2010 measures of pile driving noise levels were made in NW Scotland. Specifically, they were made during the construction of two offshore wind turbines close to a special area of conservation were a protected population of bottlenose dolphins resided. They found a decrease in sound pressure and an increase in duration with increasing distance from the pile driving site. In fact, noise levels produced during pile-driving were detectable above background underwater noise levels at a distance of 70km. These noise levels were related to noise criteria for marine mammals and they found that bottlenose dolphins and minke whales could exhibit behavioral disturbance up to 50km away and any zones of auditory injury and temporary threshold shifts were likely to have been within a range of 100m. (Bailey et al 2010)

A graph of peak to peak sound pressure levels from pile-driving activities in relation to distance from the noise source.

Another area of concern when it comes to noise pollution is the naval sonar exercises. In 1998 a letter in the journal nature attributed the cause of the atypical mass stranding of beaked whales to a naval exercise in the area. The same happened again in 2000 in the Bahamas. As of today scientists know of one or two dozen atypical strandings of beaked whales that coincided with the presence of naval ships in the area. One proposition for this is that beaked whales are especially sensitive to these noises although as of date there is no evidence to support this. Another hypothesis is that the naval sonar signals are similar to calls of killer whales which are predators of the beaked whales. It was then proposed that beaked whales may be showing antipredator response since these signals are so similar. This hypothesis was tested with three satellite tagged beaked whales that were exposed to naval sonar signals and calls of marine mammals eating whales. Although the whales didn’t show antipredator response to the extent of stranding, the whales did stop clicking in response to the sound stimulus and in particular reduced their foraging activity. (Tyack 2009)

Another area of concern is how explosives may affect marine mammals. In particular, aside from behavioral changes, how the ear may be affected from this high intensity explosions. Marine mammals evolved from land mammals and such both have similar ears. However, marine mammals have not only had to adapt their ears to the high pressures they encounter during dives but they have also had to develop adaptations to deal with the high noise environment in which they live. The two views are that since marine mammals rely so much on hearing, they can suffer impacts from even minor acoustic trauma. On the other hand, since they have adapted their ears to this high noise environment and since they rely so much on hearing for their lifestyle they are well protected. In a study by Ketten a model was used to asses theoretical pressures that marine mammals may encounter within a 15 km radius of a multi-tonnage mid water explosion. In her study she found that at certain distances and pressures, these blasts could not only cause trauma to the ear but these explosions could indeed be lethal. (Ketten 1995) in other experiments it has been found that noise produced by air gun arrays and explosives could be so intense that it could injure animals in the vicinity. In fact US regulations stipulate that such sound sources be shut down if a marine mammal enters the zone of potential injury. (Tyack 2009)

The studies that have been done so far have shown that marine mammals could indeed be harmed and affected by these anthropogenic noises. However, a lot of these studies have been species specific and it can be hard to extrapolate these results to all marine mammals since they all have different hearing sensitivities. In addition, it is hard to determine whether the responses observed in these studies are due anthropogenic noises or something else. Causation can be hard to study in the wild since there can be so many factors that come into play. Our understanding is limited and there is always the possibility that these animals have evolved to deal with all these noises and more. In fact other studies have shown that some marine mammals can compensate for noise to some point. They can increase the level of their calls, shift their signals out of the noise band or they wait to signal until the noise is reduced. Although we see that animals have been able to adapt it is noteworthy to mention that these adaptations may come with an energy expenditure to the animal. (Tyack 2009)

Future research might focus on using a software that was developed by Erbe and Farmer. They argue that to understand over which range anthropogenic noise impacts marine mammals, we need to understand how the noise propagates away from the noise source and we also need to understand the relationship between received noise levels and impact thresholds. They present a software that does both of these things and in this way we can estimates zones of impact on marine mammals around anthropogenic noises. (Herbe and Farmer 2000) Other research might also focus on controlled exposure experiments (CCEs) as proposed by Tyack et al. This type of research focuses on determining the response of animals to signals that aren’t part of their normal communicative range. Certain considerations need to be taken into account such as selection of subjects and stimuli which should be appropriate to the hypothesis and experiments should be designed to have biological relevance and test biologically significant responses. (Tyack et al 2003)

The science is hard but in due time we might be able to understand how these complex animals are affected by such a wide array of man made noises. However, once this knowledge gap is filled and we finally understand how each species is affected by different anthropogenic noises this begs the question of what will happen next. But more importantly we wonder if we will gather the knowledge in time to save some of these already at risk populations that might be deleteriously affected by anthropogenic sounds.

Works Cited:

Bailey, H., Senior, B., Simmons, D., Rusin, J., Picken, G., & Thompson, P. M. (2010). Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals. Marine Pollution Bulletin, 60(6), 888-897.

Erbe, C. (2011). The effects of underwater noise on marine mammals. The Journal of the Acoustical Society of America, 129(4), 2538.

Erbe, C., & Farner, D. M. (2000). A software model to estimate zones of impact on marine mammals around anthropogenic noise. The Journal of the Acoustical Society of America, 108(3), 1327-1331.

Ketten, D. R. (1995). Estimates of blast injury and acoustic trauma zones for marine mammals from underwater explosions. Sensory systems of aquatic mammals, 391-407.

Tyack, P. L. (2009). Human Generated Sound and Marine Mammals. Physics Today, 62(11), 39-44.

Tyack, P., Gordon, J., & Thompson, D. (2003). Controlled Exposure Experiments to Determine the Effects of Noise on Marine Mammals. Marine Technology Society Journal, 37(4), 41-53.

Small-Scale Fisheries and Food Security: Preventing Overexploitation

November 13, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By James Keegan, RJD Intern

Artisanal, or small-scale, fisheries provide food and employment to hundreds of millions of people in developing countries, making these fisheries’ sustainability essential (Johnson et al. 2013). In tropical developing countries, 60% of the people depend on fish for 40% or more of their protein demand (Hussain et al. 2010). Growth in fisheries in the developing world outpaces growth in agriculture (Garcia et al. 2010). With a growing world population, persistent problems of hunger and malnutrition afflicting developing nations will only increase, so food security is a major societal and international concern (Garcia et al. 2010). Fishery resources are important sources of nutrition for many low-income populations in rural areas, and with such a large number of people relying on small-scale fisheries to alleviate poverty and contribute to food security, their international importance continues to increase.

Fishermen sailing off the coast of Mozambique. Photo source: Wikimedia Commons

Effective consumption in developing countries may be even higher than current statistics show because frequently small-scale fisheries do not report their catch (FAO, 2014). This is often the result of subsistence fishing, in which fishermen directly rely on their catch for food. Moreover, many fishermen practice on a part-time or occasional basis, and so a census may not record them as fishers, ultimately underestimating their number (FAO, 2014). With a more accurate estimation of small-scale fisheries’ catch, their already substantial global importance would be magnified.

Because they encompass a large number of people living in communities with low adaptability and heavy dependence on fish for food, small-scale fisheries are the most vulnerable type of fishery (FAO, 2014). Small-scale fisheries face many problems such as habitat degradation, climate change, lack of financial support, poor gear and infrastructure, and the lack of access to markets (Daw et al. 2012), (Halafo et al. 2004). Moreover, many fisheries suffer from an excess of fishing effort, endangering their long-term sustainability. It is particularly difficult to address excessive fishing effort in small-scale fisheries, where there are limited options for controlling access to fish. (Daw et al. 2012).

Stilt fishermen in Sri Lanka. Photo source: Wikimedia Commons

Usually, overexploitation of fish stocks result from unsustainable practices. This includes illegal, unreported, and unregulated fishing (IUU), which threatens both the local ecosystem and the socio-economic condition of the small-scale fishing communities (FAO, 2014). IUU reduces the quality and quantity of available catch for legitimate fishers, and often contributes to poverty and food insecurity (FAO, 2014). Another issue affecting sustainability of fisheries is the post-harvest loss of fish, which can occur at any stage of the supply chain. Recent investigations have revealed a direct relationship between high fish losses and increased fishing effort which fisheries use to compensate for these losses (FAO, 2014). Moreover, because of their inefficient structure, small-scale fisheries incur greater losses than the large-scale fisheries (FAO, 2014).

Proper management can alleviate these unsustainable practices that lead to overexploitation. The management of small-scale fisheries, with their fundamental components of population, poverty and food security, remains particularly problematic, and many small-scale fisheries remain practically unmanaged (Garcia et al. 2010). However, management of small-scale fisheries has improved, and recent approaches have shown success. Institutions that manage small-scale fisheries can be locally based, state controlled, or a mix of the two. The latter arrangement, known as co-management, is the preferred approach for sustainability (Kosamu, 2015). Bottom-up implementation of new management arrangements between the state and the local community may make it easier for the two to agree on an objective, as well as help the fishers adapt to the new system (Aburto et al. 2013). Although government management is helpful, a case analysis showed that the sustainability of small-scale fisheries depended on the strength of the collective capital of the local communities (Kosamu, 2015). With weak local capital, government involvement made no difference, and the fisheries were unsustainable in all cases (Kosamu, 2015). This indicates that governments can help small-scale fisheries effectively by protecting and supporting local institutions.

Two men untangling their nets in Vietnam. Photo source: Wikimedia Commons.

In addition to effective management, the availability of alternative food and income sources to local communities can reduce fishing pressure to a sustainable level (Kronen et al. 2010). National economic development and communal income sources affect local resource exploitation, and thus, the overexploitation of fish stocks. Economically poorer regions with fewer alternative employment opportunities will suffer more from overfishing. In support of this, recent studies have found higher fish biomass densities near sites with greater infrastructure, owing to an economy less reliant on natural resource extraction (Daw et al. 2012).

Small-scale fishery sustainability remains essential to developing nations, particularly in response to growing global populations. Implementation of proper management practices as well as support of local economies will ease the pressure on local fish stocks. With sustainable fisheries, food security will increase, and the quality of life for the local community will follow.

References:

Johnson, A. E., Cinner, J. E., Hardt, M. J., Jacquet, J., Mcclanahan, T. R., and Sanchirico,J. N. (2013). Trends, current understanding and future research priorities for artisanal coral reef fisheries research. Fish Fish. 14, 281–292. doi:10.1111/j.1467-2979.2012.00468.x

Hussain SA, Badola R (2010) Valuing mangrove benefits: Contribution of mangrove forests to local livelihoods in Bhitarkanika Conservation Area, East Coast of India. Wetlands Ecology and Management 18: 321–331. doi: 10.1007/s11273-009-9173-3

Garcia, S. M., and Rosenberg, A. A. (2010). Food security and marine capture fisheries: characteristics, trends, drivers and future perspectives. Philos. Trans. R. Soc. B 365, 2869–2880. doi: 10.1098/rstb.2010.0171 FAO (2014)The State of World Fisheries and Aquaculture 2014. Rome 223 pp.

Daw, T.M., Cinner, J.E., McClanahan, T.R., Brown, K., Stead, S.M., Graham, N.A.J., Maina, J. (2012). To Fish or Not to Fish: Factors at Multiple Scales Affecting Artisanal Fishers’Readiness to Exit a Declining Fishery. PLoS ONE 7: e31460. doi:31410.31371/journal.pone.0031460.

Halafo, J.S., Hecky, R.E., Taylor, W.D., 2004. The artisanal fishery of Metangula, Lake Malawi/Niassa, East Africa. African Journal of Aquatic Science 29, 83-90

Kosamu, Ishmael B.M. (2015) Conditions for sustainability of small-scale fisheries in developing countries. Fisheries Research 161, 365-373.

Aburto, J., Gallardo, G., Stotz, W., Cerda, C., Mondaca-Schachermayer, C., Vera, K. (2013) Territorial user rights for artisanal fisheries in Chile – intended and unintended outcomes. Ocean & Coastal Management 71, 284-295.

Kronen, M., Vunisea, A., Magron, F., McArdle, B., 2010. Socio-economic drivers and indicator for artisanal coastal fisheries in Pacific island countries and territories and their use for fisheries management strategies. Marine Policy 34, 1135-1143

Atlantic Bluefin Tuna Fisheries: A Case of Mismanagement

November 10, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Hanover Matz, RJD Intern

While many fisheries around the world are currently being devastated by the overwhelming power and efficiency of modern fishing fleets, the Atlantic bluefin tuna fishery of the Atlantic and Mediterranean is one that has come to the forefront of marine conservation as an example of mismanagement and overexploitation. The bluefin tuna fishery in the Atlantic has traditionally been divided between the west Atlantic and the east Atlantic and Mediterranean stocks, with disagreements over the divisions of distinct populations (Sumaila and Huang 2012). Figure 1 shows the distribution of bluefin tuna in the Atlantic, with major spawning grounds (dark gray spotted areas) and migration routes (arrows). Tuna fishing in the Mediterranean can be traced back to ancient times, with hand lining and seine fishing practiced by peoples as early as the Phoenicians and the Romans. Fishing practices expanded into trap fishing and beach seine nets between the 16^th and 19^th centuries, and eventually were replaced by the modern industrial seine and longline fleets of the 20^th century (Fromentin and Powers 2005). It is during the late 20^th century that major changes in the total catches of bluefin tuna occurred.

Distribution of Atlantic bluefin tuna fisheries and migration routes (Fromentin and Powers 2005)

Catch data from the 1970s onward shows an increase in total catch beginning in the 1990s. Figure 2 shows bluefin tuna catches in the Atlantic from 1950 based on gear type. Bluefin tuna catches rose from levels between 5,000 to 8,000 tons in the 1970s to 40,000 tons in 1995. The International Commission for the Conservation of Atlantic Tunas (ICCAT) was established in 1969 to oversee the management of bluefin tuna, but this management has faced several issues with regards to limiting the overexploitation of tuna stocks (Sumaila and Huang 2012). One significant error on the part of ICCAT was the setting of Total Allowable Catches (TAC) above the limits suggested by advisory scientific bodies. Fromentin et al. (2014) describe the various problems that have plagued the management of bluefin tuna by ICCAT. Along with a disregard for recommended scientific limits, tuna stocks have been overfished due to the frequency of Illegal, Unreported, and Unregulated (IUU) fishing. With bluefin tuna fishing occuring over such a large expanse of ocean in the Atlantic alone, crossing waters under the control of various nations and the high seas, it is difficult to effectively enforce management policies. The authors of the 2014 report also identify how uncertainties in stock assessment have contributed to the mismanagement of bluefin tuna.

Total catch of bluefin tuna in tons by gear type since 1950, showing significant increase since the 1990s (Sumaila and Huang 2012)

Three sources of uncertainty in bluefin tuna have contributed to difficulties in establishing management policies: uncertainity in the biology and populations of tuna, poor quality of data, and errors in the ability of models to predict tuna population dynamics. (Fromentin, Bonhommeau et al. 2014). Given the migratory nature of bluefin tuna and the expanse of ocean which they inhabit, it is difficult to conduct studies on their biology and development. Catch data has also been inaccurate in the past due to the levels of illegal and unreported fishing in the industry. Finally, uncertainties in the models used to predict population dynamics make it difficult for management bodies such as ICCAT to develop effective policies. Bluefin tuna cross the Exclusive Economic Zones (EEZs) of many different countries, contributing to further difficulties in managing fish stocks that may be subjugated to fishing regulations across multiple nations (Sumaila and Huang 2012). While a better understanding of how bluefin tuna populations may overlap and mix has been established in the past decades, more research still needs to be conducted (Fromentin and Powers 2005). Another indicator that Atlantic bluefin tuna stocks have declined is the measurement of spawning stock biomass, the portion of the stock population capable of reproducing. Data since 1970 up to 2005, including both reported and illegal, unreported, and unregulated fishing, shows a decrease in spawning stock biomass by 60% since 1974 (Sumaila and Huang 2012). This means that overfishing may not only be reducing current populations, but hindering their ability to reproduce by depleting the number of reproductive individuals.

In response to increased fishing pressure on bluefin tuna stocks and decreased catches, aquaculture of tuna now occurs in several regions. Figure 3 shows current locations of tuna aquaculture. Starting with the cultivation of Atlantic bluefin tuna in Canada and Pacific bluefin tuna in Japan in the 1960s, farming of tuna has spread to the Mediterranean and Australia. However, most of this farming consists of capturing wild tuna and fattening them in pens for later harvest, while it still remains incredibly difficult and costly to rear tuna from larvae to adults. This method of catching wild tuna in seine nets and fattening them most likely does not help contribute to alleviating fishing pressures on wild stocks (Metian, Pouil et al. 2014)

Global distribution of bluefin tuna farms (Metian, Pouil et al. 2014)

Given the current level of harvesting, better management of Atlantic bluefin tuna needs to be put in place. The capacities of the purse seine net fleet and longline fleet in the Atlantic already exceed the mean productivty of bluefin tuna (Fromentin and Powers 2005). Even if there are uncertaintities in the measurements of tuna productivity, the status of tuna populations is precarious enough that it would be risky to continue the current fishing effort. Sumalia and Huang (2012) make several policy recommendations to better manage Atlantic bluefin tuna stocks. First, the total allowable catch needs to be reduced to levels as recommended by scientific research. Second, a better detection and penalty system needs to be established in order to reduce illegal fishing. Finally, the establishment of Marine Protected Areas and the listing of Atlantic bluefin tuna as endangered on the Convention for International Trade in Endangered Species (CITES) would afford tuna some protection to allow populations to recover. However, the multinational fishing effort and policy formation process of ICCAT has made it difficult to come to reasonable agreements between nations to manage tuna. To protect this valuable species, action needs to be taken to reduce the current fishing effort and total allowable catch. Better scientific research will provide more effective management tools, but the current advice being given by scientific bodies needs to be headed when establishing catch limits. If Atlantic bluefin tuna stocks are to continue to provide a valuable resource of seafood to world markets, a more sustainable fishery needs to be established.

References

Fromentin, J.-M., S. Bonhommeau, H. Arrizabalaga and L. T. Kell (2014). “The spectre of uncertainty in management of exploited fish stocks: The illustrative case of Atlantic bluefin tuna.” Marine Policy 47: 8-14.
Fromentin, J.-M. and J. E. Powers (2005). “Atlantic bluefin tuna: population dynamics, ecology, fisheries and management.” Fish and Fisheries 6: 281-306.
Metian, M., S. Pouil, A. Boustany and M. Troell (2014). “Farming of Bluefin Tuna–Reconsidering Global Estimates and Sustainability Concerns.” Reviews in Fisheries Science & Aquaculture 22(3): 184-192.
Sumaila, U. R. and L. Huang (2012). “Managing Bluefin Tuna in the Mediterranean Sea.” Marine Policy 36(2): 502-511.

Effect of Climate Change on Pacific Tuna Stocks

November 7, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Beau Marsh, RJD Intern

Pacific tuna fisheries are essential to the livelihood, sustainability and well-being of many Pacific islands, they acts as an important food source, as well as a lucrative activity for local economies. The species of tuna composing these fisheries are Skipjack (Katsuwonus pelamis), Yellowfin (Thunnus albacares), Bigeye (Thunnus obesus), and Albacore (Thunnus alalunga). Skipjack are particularly significant because they regularly make up more than 60% of the Pacific tuna catch (Ganachaud et al., 2013). It is important to learn as much as possible about the conditions in which the different tuna species spend their time, so habitat shifts in response to climate change and El Nino Southern Oscillation (ENSO) can be anticipated.

Tuna are considered thermoregulators (Lehodey et al., 2010). This means that they can tolerate a greater range of temperatures by maintaining a fairly constant internal temperature. The mechanism by which this is possible is called countercurrent heat exchange, through which their circulatory system conserves heat more effectively (Lehodey et al, 2010). This mechanism is more developed in certain tuna species, so different species occupy different parts of the water column based on temperature. Adult Skipjack reside in waters ranging from 20-29 degrees Celsius (Ganachaud et al., 2013). Other species, including Bigeye and Albacore, are capable of living at cooler temperatures, allowing them to dive to deeper depths. Bigeyes can dive to around 600 meters in about 5 degree Celsius water (Brill et al., 2005), whereas Skipjack are restricted to the upper 200 meters (Lehodey et al., 2010).

These environmental conditions do not apply to tuna larvae. In the larval stage, tuna are more sensitive to environmental factors. They require stricter physical and chemical conditions. The different species’ larvae spend all their time at the surface where the warmest water and food supplies are consistent (Brill et al, 2005). Distributions of tuna depend on horizontal stratifications by temperature, as well as the depth of the mixed layer (Ganachaud et al., 2013). Ideal conditions are formed by the convergence and divergence of ocean currents that create thermal fronts, locations of upwelling, and eddies (Langley et al, 2009). These physical boundaries, combined with foraging areas, dictate tuna distributions basin-wide.

The physical boundaries are the Pacific Equatorial Divergence (PEQD), the West Pacific Warm Pool (WPWP), the North Pacific Subtropical Gyre (NPSG), and the South Pacific Subtropical Gyre (SPSG) (Ganachaud et al., 2013). In the case of the Skipjack, over 90% of the population resides in the WPWP, specifically, along the eastern front at its boundary with the PEQD (Fig.1) (Ganachaud et al., 2013).

SST and superimposed Pacific hydrological factors (Ganachaud et al, 2013).

In contrast to the WPWP, the waters of the central and eastern Pacific are characterized by higher salinity (>35 psu) and increased concentration of nutrients (Maes et al, 2006). This is explained by the strong wind-driven upwelling that takes place along the west coast of South America and the Ekman-driven divergence that occurs in the Central Equatorial Pacific (Picaut et al, 2001). Due to the strong difference between the WPWP and the PEQD, the boundary of these water masses exhibits unique physical, chemical and biological characteristics and is the location of most tuna fisheries in the Pacific (Lehodey et al, 2010). Although the abundance of tuna in warm, oligotrophic waters in the WPWP is counter-intuitive at first glance, convergence zones such as the one between the WPWP and the PEQD are known to act as aggregating mechanisms of plankton and micronekton and, subsequently, large predators.The western equatorial Pacific presents one of the most prolific areas for tuna in terms of spawning and foraging grounds (Ganachaud et al, 2013). Formed by the wind-driven South Equatorial Current (SEC), the WPWP is characterized by the highest sea surface temperature of the world’s oceans (often reaching more than 30°C) and low sea surface salinity caused by increased precipitation (McPhaden and Picaut, 1990; Picaut et al, 2001; Maes et al, 2006). As a result of this accumulation of water in the western Pacific, the thermocline in the WPWP is considerably deeper than along the central and eastern Pacific; this inhibits deep vertical mixing and makes the WPWP an area of low nutrients and low primary productivity (Picaut et al, 2001).

Schematic drawing illustrating a possible aggregation mechanism for plankton and micronekton (Yoder et al, 1994)

The WPWP-PEQD convergence boundary is not static; it’s modulated by the extent and location of the WPWP and has a well defined interannual variability that is strongly linked to the phase of ENSO. McPhaden and Picaut (1990) first observed the migration of the WPWP in relation to ENSO; they reported a strong eastward displacement of the eastern boundary of the WPWP during El Niño and associated this shift to a reversal of the SEC caused by weakened trade winds. Later, Lehodey et al (2010) reported a strong correlation between the location of the WPWP-PEQD boundary (using the 29° C isotherm as a proxy), the abundance of Skipjack tuna and the phase of ENSO; they reported clear eastward population shifts during the warm phase of ENSO. Other approaches have been used to ascertain the location of the convergence zone and its variability; Maes et al (2006) identified a strong salinity gradient (0.4 psu over 10°-15° in longitude) to be a more accurate indicator, and more recently have used satellite-based ocean color observations to detect the eastern edge of the WPWP (Maes et al, 2006).

In an attempt to incorporate climate change predictions into tuna population models, Lehodey et al (2010) forecast the distribution of Bigeye tuna in the Pacific. Results of this study showed an expansion of favorable spawning area towards mid-latitudes and to the eastern Pacific; in contrast, the WPWP became too warm and oxygen depleted to sustain stable populations of tuna by the end of the century.

Ganachaud et al (2013) documented changes in oceanographic parameters of importance to tuna distribution in the Pacific. They reported a large-scale shoaling of the thermocline, increasing stratification and limiting nutrient provision to the biologically active layer. They also highlight changes in oceanic currents such as the strengthening of the NEC which they hypothesize could modify the supply of iron in the eastern Pacific. Ganachaud et al (2013) anticipate an eastward migration of the WPWP-PEQD boundary by 6,000 (±2,000) km.

Global warming will affect the ocean’s physical, chemical and biological characteristics and those changes will have an impact on fisheries and its fish-dependent communities (Hollowed at al, 2013). The extent to which fisheries will be able to continuously provide food for millions of people is contingent upon our understanding of future distributions and abundance of commercially important species such as tuna.

Attempts should be made to provide new insight into future spawning and foraging favorable grounds for tuna in the Pacific Ocean. Traditionally, the areas near the NPSG and the SPSG have been overlooked and categorized as low productivity areas. Nevertheless, the NPSG-PEQD and SPSG-PEQD boundaries might exhibit similar oceanographic characteristics to those found in the convergence zone at the WPWP-PEQD boundary and it is possible that under a global warming scenario these areas will become more favorable for tuna populations. Efforts should be made to ascertain the suitability of these regions as potential future tuna habitats.

References

Brill, R. W., Bigelow, K. A., Musyl, M. K., Fritsches, K. A., & Warrant, E. J. (2005). Bigeye Tuna (Thunnus obesus) Behavior And Physiology And Their Relevance To Stock Assessments And Fishery Biology, 57(2), 142–161.

Ganachaud, A., Sen Gupta, A., Brown, J., Evans, K., Maes, C., Muir, L. C., & Graham, F. S. (2013). Projected changes in the tropical Pacific Ocean of importance to tune fisheries. Climatic Change, 119, 163-179.

Hollowed, A., Barange, M., Beamish, R., Brander, K., Cochrane, K., Drinkwater, K., Foreman,G.,Hare,J., Holt,J., Ito,S., Kim,S., King,J.R.,Loeng,H., MacKenzie,B.R., Mueter,F.J., Okey,T.A., Peck, M., Radchencko,V.I., Rice,J.C., Schirripa,M.J., Yatsu,Y., Yamanaka,Y.. (2013). Projected impacts of climate change on marine fish and fisheries. ICES Journal of Marine Science, 70(5), 1023-1037.

Langley, A., Briand, K., Sean, K. D., & Murtugudde, R. (2009). Influence of oceanographic variability on recruitment of yellowfin tuna (thunnus albacares) in the western and central Pacific Ocean. Canadian Journal of Fisheries and Aquatic Sciences, 66, 1462-1477.

Lehodey, P., Senina, I., Sibert, J., Bopp, L., Calmettes, B., Hampton, J., & Murtugudde, R. (2010). Preliminary forecasts of bigeye tuna population trends under the A2 IPCC scenario. Progress in oceanography, 86, 302-315.

Maes, C., Ando, K., Delcroix, T., Kessler, W., McPhaden, M., & Roemmich, D. (2006). Observed correlation of surface salinity, temperature and barrier layer at the eastern edge of the western Pacific warm pool. Geophysical Research Letters, 33. doi: 10.1020/2005GL024772

McPhaden, M., & Picaut, J. (1990). El Nino-Southern Oscillation Displacements of the Western Equatorial Pacific Warm Pool. Science, 250, 1385-1388.

Picaut, J., Ioualalen, M., Delcroix, T., Masia, F., Murtugudde, R., & Vialar, J. (2001). The oceanic zone of convergence on the eastern edge of the Pacific warm pool: A synthesis of results and implications for El Nino-Southern Oscillations and biogeochemical phenomena. Journal of Geophysical Research., 106, 2363-2386.

Yoder, J., Ackleson, S., Barber, R., Flament, P., & Balch, W. (1994). A line in the sea. Nature, 371, 689-692.

The Mess Left by the Gulf Oil Spill

November 5, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Jessica Wingar, RJD Intern

Oil spills are notoriously awful environmental events. The worst one to ever occur was on April 2, 2010 in the Gulf of Mexico. One of the Deepwater Horizon oil rigs exploded, killing eleven people, and causing copious gallons of oil to pour into the ocean. After eighty seven days, the rig was capped off, but the damage was already done. The environmental consequences of this spill are very wide ranging. The estimated amount of oil that spilled into the ocean is about 4.9 million barrels and that is probably a low estimate. With this amount of oil and because of ocean currents, this oil spread all around the Gulf of Mexico and into the entire water column. Of course, the animals living in this oil were and still are greatly affected by this spill, and future generations will continue to be effected. From stranded dolphins to oil covered turtles, the list goes on (Gulf Oil Spill).

An immediate effect of the oil spill: A scientist saving an oil covered turtle.

In addition, to the visible effects, there are many effects of the oil spill that occurred under the surface. Oil contains petroleum hydrocarbons, which are pollutants meaning that they are harmful to organisms that ingest them. These hydrocarbons can lead to the suppression of the immune system, which increases the likelihood of disease in populations. Therefore, increasing the likelihood of death in these organisms, and thus decreasing the populations of many organisms. The effects of these hydrocarbons also lead to a decrease in ability to respond to large changes in environmental factors (Whitehead, A, 2014). However, there are more than just the effects on the present populations of marine organisms. There are many consequences of the spill that will be felt for generations to come.

The effects of oil on the development of fish are of high concern. It is of high concern because the oil from the rig has gone throughout the water column and to the surface. Many fish embryos develop in the surface water. Before the spill, the effect of a lot of crude oil was not an issue, but after this huge spill the worry of developmental problems has increased (Incardona, J.P., 2014).

Many studies have been done since the spill that observe the changes in fish development. One study conducted shortly after the spill looked at developing killifish embryos and adult organisms in order to see how they reacted to the oil. These fish were taken from marshy areas that had been directly affected by the fallout of the deepwater horizon spill. PCB is one of the main toxins in crude oil and these embryos exhibited activation of PCB responsive genes. Therefore, leading to decreased hatching, development, and survival of killifish. These effects are major concerns because killifish are the most abundant vertebrates in the Gulf of Mexico marshy environments (Whitehead, A. et al, 2012). In a study done using oil taken from the slick, amberjack, Bluefin tuna, and yellowfin tuna were raised in a lab and their heart development was observed. As the concentration of oil increased, heart rate decreased and arrhythmia was also observed. In addition to the problems in heart development, there were also physical developmental problems. Fins appeared to be reduced in size and there was decreased development of finfolds (Incardona, J.P., 2014). Another study observing mahi-mahi also showed an increase in heart rate as percentage of oil increased. These important pelagic species also had swimming challenges as they grew.

Affects on the caudal finfolds

This same study looked at how the swim speed of mahi-mahi was affected by the Deepwater Horizon oil spill. The mahi were exposed to oil as embryos for 24 and 48 hour periods. Both time exposures showed that when these fish grew to juveniles they experienced a decrease in swim speed that they could maintain for long periods of time. Since it took about 25 days for these decreases to be seen, this study also found that there must be some delay in development as well caused by the polycyclic aromatic hydrocarbons, toxins, in the crude oil from the Deepwater Horizon Spill (Mager, E, 2014). Research is still continuing in order to find out more of the long term effects of this devastating oil spill. This research is increasingly important seeing as in years to come, these effects could be more pronounced in the ocean. In addition, if this research is done, then further work can be done to conserve the organisms that currently live in the Gulf of Mexico.

References

Gulf Oil Spill. (n.d.). Retrieved October 27, 2014, from http://ocean.si.edu/gulf-oil-spill

Incardona, J.P., Gardner, L.D., Linbo, T.L., Brown, T.L., Esbaugh, A.J., Mager, E.M., Stieglitz, J.D., French, B.L., Labenia, J.S., Laetz, C.A., Tagal, M, Sloan, C.A., Elizur, A, Benetti, D.D., Grosell, M, Block, B.A., and Nathaniel L. Scholz. (2014). Deepwater Horizon crude oil impacts the developing hearts of large predatory pelagic fish. Proceedings of the National Academy of Sciences, 111(15): 7053-7061.

Mager, E.M., Esbaugh, A.J., Stieglitz, J.D., Hoenig, R, Bodinier, C, Incardona, J.P., Scholz, N.L., Benetti, D.D., and Martin Grosell. (2014). Acute Embryonic or Juvenile Exposure to Deepwater Horizon Crude Oil Impairs the Swimming Performance of Mahi-Mahi (Coryphaena hippurus). Environmental Science and Technology, 48(12): 7053-7061.

Whitehead, A. (2013). Interactions between Oil-Spill Pollutants and Natural Stressors Can Compound Ecotoxicological Effects. Integrative and Comparative Biology, 53 (4): 635-647.

Whitehead, A, Dubansky, B, Bodinier, C, Garcia, T.I., Miles, S, Pilley, C, Raghunathan, V, Roach, J.L., Walker, N, Walter, R.B., Rice, C.D., and Fernando Galvez. (2012). Genomic and physiological footprint of the Deepwater Horizon oil spill on resident marsh fishes. Proceedings of the National Academy of Sciences, 109 (50): 20298-20302.