Conservation – Page 24 – Shark Research & Conservation Program (SRC)

A changing climate impacts fish distributions

November 10, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By Grace Roskar, RJD Intern

Long-Term Changes in the Distributions of Larval and Adult Fish in the Northeast U.S. Shelf Ecosystem

Fishing pressure and climate change have been linked to changes of the distribution of several fish species in past studies. These factors contributed to geographic shifts of fish populations to different areas and impacted the abundances of adult fish. In this study, researchers at NOAA studied initial stages of fish species’ life cycles to examine how these fish distributions have changed over time and space.

Many fish species switch habitats during different parts of their lives. Most fish species in the Northeast U.S. (NEUS) Shelf Ecosystem produce pelagic eggs. Pelagic eggs float among currents in the open ocean. The eggs hatch into larvae, grow into juveniles, and finally become adults. Since these different life stages often utilize different habitats, at the end of one stage, fish need to be ready to move to a new habitat for the next part of their lives. Past research has focused more on the adult stage than the larval stages. However, the early life stages of fish are critical because a species’ population abundance can be greatly affected by the survival rates of those earlier stages.

This photo shows a larva from the Scombridae family, which includes mackerels, tunas, and bonitos. The Scombridae family was one of fish families sampled by NOAA. Photo credit: NOAA http://www.sefsc.noaa.gov/species/fish/larval/photos_larval.htm

In this study, data from the NOAA Northeast Fisheries Science Center was used to analyze larval distributions in the NEUS Shelf. Past analyses showed that the adult fish distributions in this region have generally shifted towards the north or into deeper water. This study examined two time periods (1977-1987 and 1999-2008). The goals of Walsh et al. (2015) were to “1) examine changes in the spatial distributions of larval fish…2) examine changes in larval seasonal occurrence…3) compare changes in larval distributions to changes in adult distributions, and 4) evaluate changing distributions relative to regional occurrence, timing of larval occurrence, management status of adults, and habitat used by adults.” Larval fish samples were collected from the NEUS Shelf from North Carolina to Nova Scotia by two survey programs. Adult fish samples were collected using bottom trawl surveys over the same area and timeframe.

This figure shows the regions along the NEUS Shelf where sampling occurred. (Walsh et al. 2015)

The results showed that 43% of larval species and 50% of adult species changed distribution. The changes in larval distribution indicate changes in “spawning, currents, survival, or some combination of the three,” (Walsh et al. 2015). This emphasizes the need for further examination into how each stage of the life cycle is connected in these regions. Around 50% of the total taxa exhibited a change in direction, either along the shelf, across the shelf, into deeper waters, such as the movement of Atlantic cod (Gadus morhua), or a combination of these. Most directional changes were towards the north, perhaps an effect of rising temperatures. For 60% of the taxa surveyed, “distribution changes differed between adult and larval stages,” indicating changes in the overall habitat range that species utilize throughout their lives (Walsh et al. 2015). This could be problematic for species if the distribution changes create longer migrations or longer distances between nursery and feeding grounds. These changes in distribution and life stages have significant ramifications for fisheries. When the distribution of a life stage is altered, the stock of the species changes, which can lead to different outcomes for the fishery each year.

Certain off-limits areas in the NEUS Shelf are meant to protect certain species by enforcing fishing regulations. However, when distributions change, the closings could be inadequate at protecting a species if the species simply is not there. Moreover, changes in larval fish distributions can have impacts on the whole ecosystem. For example, if populations are shifting northward, the larvae can be subject to new predators and interactions in the food web. This study showed distributional changes in both larval and adult fish taxa in the NEUS Shelf region. Of importance is that these are complex changes with many factors, such as timing and regional occurrences, which will affect the assessment and management of these resources.

References:

Walsh H.J., Richardson D.E., Marancik K.E., Hare, J.A. 2015. Long-Term Changes in the Distributions of Larval and Adult Fish in the Northeast U.S. Shelf Ecosystem. PLoS ONE 10(9): e0137382. doi:10.1371/journal.pone.0137382

The effect of environmental factors on fish movements

November 4, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By William Evans, RJD Intern

Assessing environmental correlates of fish movements on a coral reef by Currey, et al. discusses the movement of fish dependent on environmental conditions. In this study, the researchers aimed to determine if environmental factors changed the location of Lethrinus miniatus, also known as the redspotted sunfish, on the reef to then make assumptions about the movement of that species as environmental factors change over time. There has been research done to show how fish react to changes in environmental stimuli but in relation to the environmental stimuli causing biological and behavioral alterations. In certain species, these alterations can be decreases in reproductive performance and slower growth rates.

The researchers sampled at Heron Island Reef in the southern portion of the Great Barrier Reef. The fish were captured, using a rod and reel on the reef slope by using a bait of pilchard and squid as bait. They were captured using barbless 8/0 and quickly vented and anaesthetized with Aqui-S. Once captured, a V13P transmitter with pressure sensor capabilities was surgically implanted in the abdominal cavity of each fish between the pectoral and ventral fins on the left side. The fish were recovered in fresh sea water and then released at the same capture site. The capture, venting and tagging process occurred in 8 minutes or less.

Each transmitter produced a different identification code of the same frequency to then relay data to the depth of that specific fish, with a maximum of 50 meters deep. To receive the data, 25 VR2 W acoustic receivers were deployed on the reef slope. Nineteen of the receivers were deployed on the reef slope and the other six were deployed in the lagoon. This arrangement of receivers was designed for a full year, of data collection and could detect acoustic transmitters within 270 m and 25 m deep. A total of sixty fish were tagged over three trips of twenty fish each: April 2011, February 2012, and September 2012.

The Facility for Automated Intelligent Monitoring of Marine Species sensor network and Great Barrier Reef Ocean Observing System mooring collected environmental data from April 2011 to September 2013 by on site monitoring. This environmental data included water temperature, atmospheric pressure, wind speed and direction, rainfall, and moon phase. The means of this data were averaged daily and weekly because of the vast amount of data collected over an extended period of time. These specific parameters were chosen because they were hypothesized to be the potential causes of reef movement among L. miniatus. Included in the biological parameters that were assessed, fork length (FL) was used to also determine if there was an effect based on fish size.Atmospheric pressure and wind direction data were not included in the final analysis because atmospheric pressure was correlated with water temperature and the data for wind was determined to be unbalanced because of the direction that the wind came.

Fish were used in the final analysis when they were detected for more than 5 days and when a receiver recorded the same fish presence more than once in the same day. From the 60 L. miniatus originally tagged, only 26 were able to be used for the final data analysis. These fish ranged in fork length from 372 mm to 493 mm and we detected from 2 to 52 weeks throughout the study by the receivers. The data was processed using sixteen sub-models to analyze the environmental effects of reef presences of L. miniatus. One of the models predicted that there would be less than a 50% presence of them on the reef slope if the daily mean water temperature was greater than 24°C. All of the other parameters that were measured were not considered to be important for this specific study. From using this temperature data and tracking the fish for up to 12 months, the researchers could make some predictions about temperature change and the effect it could have on fish on the reef, specifically L. miniatus. The data displayed that as water temperature increased, the presence of L. miniatus on the reef decreased.

Most of the studies concerning the effects of temperature on fish are about the biological changes in the fish such as changes in metabolism and sexual behaviors. This study can help predict the distribution of L. miniatus as temperatures increase or change their location in the water column in order to be at their preferred temperatures. Additionally, because increasing temperature was the main factor in determining the presence of L. miniatus on the reef, the researchers can infer that as temperature increases, the presence of the species will reduce on the reef slope. Although this study was only based around one species, this research can benefit managers in helping them understand how climate change will effect the movement of reef fishes and how the fishery will be impacted over time.

References:

Currey, Leanne M., Heupel, Michelle R., Simpfendorfer, Colin A., Williams, Ashley, J. (2015). Assessing environmental correlates of fish movement on a coral reef. Coral Reefs.

Donelson JM, Munday PL, McCormick MI, Pankhurst NW, Pankhurst PM. (2010). Effects of elevated water temperature and food availability on the reproductive performance of a coral reef fish. Mar Ecol Prog Ser 401:233–243.

Munday P, Kingsford M, O’Callaghan M, Donelson J. (2008a). Elevated temperature restricts growth potential of the coral reef fish Acanthochromis polyacanthus. Coral Reefs 27:927–931.

Baleen whales host a unique gut microbiome with similarities to both carnivores and herbivores

November 2, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By Julia Whidden, RJD Graduate Student

“Microbiome” is the term used to describe the communities of microorganisms that live inside a host, and includes microorganisms that are beneficial, detrimental, and neutral to host health. Some of these microorganisms are vital to digestion, but the diversity, composition, function, and source of an animal’s microbiome is still largely understood. For example, the microbiome of the herbivorous panda bear was expected to host communities similar to other herbivores with the same diet, while in actuality its communities were discovered to be more similar to other closely related yet omnivorous pandas. Cetaceans, or dolphins and whales, evolved from artiodactyls, which were terrestrial animals that fed on plants. Other modern-day animals evolved from artiodactyls include cows and hippopotamuses, or ruminants, and are similar to this ancestor in their herbivorous diet. The main polysaccharide, or large carbohydrate that herbivores acquire from their diet is cellulose. Whales, however, are carnivorous. Even baleen whales that are filter feeders consume small fish and crustaceans, digesting another large carbohydrate, chitin, from the ‘shells’ of their prey. Despite vastly different diets, ruminants and whales share a multichambered foregut, which is used in these animals to help digest the tough structure of the large polysaccharides they consume. This study investigated the microbiome of baleen whales to determine whether their community composition was more similar to their ancestor and distant relatives, the herbivores, or to their carnivorous diet.

Fecal samples were collected from wild baleen whales in the Bay of Fundy, Canada, in August 2011, and were complemented by samples of captive cetaceans and wild terrestrial animals. The wild fecal samples were obtained by first locating and identifying the whales, and then samples were scooped from the water immediately following defecation. Captive cetacean and wild terrestrial animal samples included Pacific Humpback whales, Atlantic white-sided dolphins, bottlenose dolphins, Beluga whales, hippopotamus, and other unnamed wild terrestrial carnivores and herbivores. DNA extraction from the fecal samples isolated 16S ribosomal RNA (rRNA), which is involved in protein synthesis in ribosomes. An analysis of 16S community sequence was performed, which indicates the diversity in a microbiome by identifying the number of gene variants present, assuming each microorganism has a different variant of the gene. The microbiome diversity within each group of animals – including the baleen whales, toothed whales, terrestrial herbivores, and terrestrial carnivores to name a few – was then compared (see Figure 1 below).

Results indicated that the microorganisms of the baleen whale’s microbiome involved in the digestion of polysaccharides were similar to those of terrestrial herbivores. This is intuitive, as the chitin that the baleen whales consume is similar in structure and function to the cellulose that herbivores consume. Further, the baleen whale microorganisms responsible for breaking down proteins and building amino acids – which make up proteins – were more similar to the microbiome of the terrestrial carnivores analyzed. This study concluded that microbiome composition is determined by a mix of the host’s past and present, incorporating microorganisms associated with their ancestor’s diet, as well as their modern diet.

What happens to the seahorses that you accidentally land in your trawl net?

October 28, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By Stephen Cain, RJD Intern

For millennia our ancestors fished the world’s oceans. Today’s fishing fleets are the most effective in all of human history, extracting ever-larger quantities of wild fishes. Only recently have scientists shown that seas are vulnerable to overexploitation, which can put species at extinction risk. Meanwhile, human population growth places increased pressure on marine resources to feed billions, thus representing a significant share of global trade.

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) is a multinational treaty with the mandate of monitoring and regulating species trade such that wild populations remain healthy. But do large, multi-national efforts such as CITES actually work? Writing in Aquatic Conservation: Marine and Freshwater Ecosystems, researchers Sarah Foster, Stefan Wiswedel and Amanada Vincent attempt to answer this question by analyzing CITES data and by using seahorses (Hippocampus) as a case study.

2002 was a noteworthy year for CITES. For the first time in nearly 25 years the international body added a marine fauna, seahorses, to its list of Appendix II species. According to the agreement, such species are of a conservation concern in the absence of regulation, and any of the 180 member nations trading in Appendix II species must demonstrate through monitoring that trade does not harm wild populations. Previous biologic surveys of seahorses analyzed by Foster et al. showed that extensive trade existed. The genus’ life-history characteristics, such as small home ranges, low fecundity and density gave scientists cause for concern over the long-term sustainability of global populations.

Photo Credit: Sarah Foster

Foster and her team reviewed CITES monitoring reports for the first seven years of the Appendix II listing (2004-2011). They wanted to determine its successes and obstacles, as well as uncover key relationships between market demand, trade routes, and the sources of trade.

Surveys undertaken prior to the implementation of the CITES listing showed that millions of individuals were traded annually. Seahorses were exported primarily as dried specimens for traditional Chinese medicine (TCM), and to a lesser degree as live individuals for aquaria. Remarkably, commercial trawlers that obtained seahorses as by-catch or non-targeted species met the larger demand for TCM markets. When seahorses were specifically targeted as catch, they were taken alive and destined for the aquaria trade. The United States imported the largest number of live seahorses during the study period.

In all, Foster et al. identified 31 out of 47 species of the genus Hippocampus as important species to international trade, four of which dominated by volume (H. kelloggi, H. kuda, H. spinosissimus, and H. trimaculatus). The top four, the authors noted, are species listed as threatened by the IUCN.

While reporting gaps and inconsistencies made definitive findings challenging, Foster and her team suspect that it is unlikely that the demand for seahorses has diminished in the years following the CITES designation. Monitoring of trade emerged as one of the greatest challenges for the treaty. Some countries known to export quantities of seahorses did not report. Other countries failed to specify the unit volumes of exports, which made it difficult to form a clear picture of international trade. Taken together, however, Foster et al. interpreted the monitoring failures as an area of opportunity for CITES.

The challenge now is for international authorities to build member capacity in annual reporting. For this, the researchers suggested that automated record validation, a process aided by new technology, could add precision to the accounting of imports and exports. In addition, standardized educational materials for species identification could strengthen the accuracy of reporting, and trade surveys could give a fresh perspective on species abundance. The promptness of the reporting also needs improvement. In some instances a country’s current reporting period represented data collected two years prior.

The measures of success for a CITES listing really come from accurate longitudinal data. As long as countries around the globe participate in and strengthen monitoring practices, Foster and her team are confident it can be a useful tool in the conservation of species. But the team is cautious in the case of seahorses. CITES listings may have little bearing on species caught as by-catch. Commercial fishers who cash in on seahorses from by-catch are capitalizing on a market demand for a fishing pressure that they have already exerted, even if accidentally. The question of whether or not they can undo that pressure, either by altering gear types or by releasing non-targeted species, is a complicated one. In the end, the decision may not rest squarely on the shoulders of the international community, but on our species.

You can find this paper in Aquatic Conservation: Marine and Freshwater Ecosystems

Foster, S., Wiswedel, S., & Vincent, A. (2014). Opportunities and challenges for analysis of wildlife trade using CITES data – seahorses as a case study. Aquatic Conservation: Marine and Freshwater Ecosystems, http://doi.org/10.1002/aqc.2493

For the latest on seahorse research, conservation, and news, see Project Seahorse

http://seahorse.fisheries.ubc.ca/

Can Marine Protected Areas Help Conserve Intertidal Species?

October 27, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By Hannah Calich, RJD Graduate Student

The giant limpet (Patella ferruginea; Figure 1) is one of the most endangered species in the Mediterranean Sea. As with many other marine species, their population decline has been attributed to overexploitation by humans. Giant limpets are most commonly harvested for food, fishing bait, or shell collection.

A giant limpet. Photo by: Jan Delsing / Wikipedia Commons

Much of the giant limpet’s remaining population is found within Sardinia’s marine protected areas (MPAs) and national parks. The population found within the Penisola del Sinis – Isola di Mal di Ventre MPA, is particularly important because despite being home to only a few hundred individuals this population has strong genetic differentiation, which is important for population recovery.

Unfortunately, giant limpets are being illegally harvested from within the Penisola del Sinis – Isola di Mal di Ventre MPA. In light of this finding, Coppa et al. (2015) set out to determine how much protection MPAs provide for intertidal species. Specifically, Coppa et al. (2015) investigated how site accessibility (semi-accessible vs. hardly accessible) and legal protection (high, medium, and limited protection) impact poaching levels and population size of the giant limpet within the Penisola del Sinis – Isola di Mal di Ventre MPA (Figure 2).

Map of Penisola del Sinis – Isola di Mal di Ventre MPA that highlights accessibility levels and protection zones. Zones A, B, and C have high, medium, and limited legal protection, respectively. Figure from Coppa et al. (2015)

The results of annual field surveys in 2011 and 2013 showed that the total population of giant limpets has declined 52% in two years as a result of illegal harvesting. However, this decline was not consistent throughout the MPA. There was a significantly higher density of giant limpets in hardly accessible sites compared to easily accessed sites. Additionally larger individuals, which are targeted by poachers, were predominantly found in sites with maximum legal protection that were hard to access. If the current levels of illegal harvesting continue the authors predict that the giant limpet may face local extinction within the next 10 years. These results suggest that this MPA is only protecting limpets in certain areas and unfortunately, this protection is insufficient.

Local people collecting intertidal invertebrates within Penisola del Sinis – Isola di Mal di Ventre MPA. Photo from Coppa et al. (2015)

The results of this study emphasize the fact that simply implementing an MPA is not necessarily sufficient to ensure species protection. This is particularly true for intertidal species that are easily accessed by illegal harvesters. Coppa et al. (2015) suggest that joint efforts between enforcement agencies, regulators, and researchers are a crucial component to ensure MPAs are able to meet their conservation objectives.

Reference:

Coppa, S., De Lucia, G. A., Massaro, G., Camedda, A., Marra, S., Magni, P., Perilli, A., Di Bitetto, M., Garcia-Gomez, J. C., Espinosa, F. (2015). Is the establishment of MPAs enough to preserve endangered intertidal species? The case of Patella ferruginea in Mal di Ventre Island (W Sardinia, Italy). Aquatic Conservation Marine and Freshwater Ecosystems. DOI: 10.1002/aqc.2579

Conservation of Amsterdam Albatrosses

October 13, 2015/2 Comments/in Conservation, Ocean News /by aanstett

By Samantha Owen, RJD Intern

This paper outlines the current conservation efforts for the Critically Endangered Amsterdam albatross (Diomedea amsterdamensis) and the threat posed by industrial longline fisheries. In 2007 a population survey estimated that there were only 167 Amsterdam albatrosses in the world. This is largely because they are only found in one place, Amsterdam Island, in the southern Indian Ocean. Their population declined dramatically in the 1960s and 1970s due to the increase in industrial longline fishing targeting bluefin tuna. While diving below the surface of the water when feeding, birds can be accidentally hooked or entangled in the longlines.

Like most albatrosses, this species is a biennial breeder, which means they only breed every other year. In between breeding years, they spend the entire break year roaming at sea. A successfully mated pair will produce only one egg per breeding year. This means that with such a small population, any mortality could have a huge impact on the viability of this species. The established threshold to trigger a population decline is a loss of more than six individuals to bycatch per year. The potential number of individuals removed from the Amsterdam albatross population each year due to longline fishing is 2-16 depending on whether mitigation measures such as tori lines, plastic streamers trailing from the back of the boat used to scare birds away, were systematically employed.

This paper quantifies the potential threat from industrial longline fishing fleets to the Amsterdam albatross based on time of year and life stages. It shows that even though the Amsterdam albatross is potentially in contact with longline fisheries at every stage of its life, non-breeding individuals have a much higher susceptibility due to their significantly increased roaming area during their break year at sea. The time of year when Amsterdam albatrosses are at the highest risk for mortality as a result of bycatch in longlines is the austral winter (July, August, September) when fishing fleets are targeting albacore and other tunas.

The Taiwanese longline fishing fleet poses the greatest threat to Amsterdam albatrosses, followed closely by the Japanese fleet. One reason it is thought that the Taiwanese fleet has such a high impact on the Amsterdam albatross is because they deploy the most longlines in the waters immediately adjacent to the species’ home, Amsterdam Island.

In conclusion, this paper states three recommendations for further conservation efforts. First, increasing the coverage of fishing operations by dedicated observers in the distribution range of the Amsterdam albatross during the austral winter. This would ensure the successful implementation of bycatch mitigation measures such as tori lines. The second recommendation is for Regional Fisheries Management Organizations (RFMOs) such as the Indian Ocean Tuna Commission (IOTC) to require all operating vessels to report ring recoveries. All Amsterdam albatrosses have been fitted with leg bands (rings) identifying each individual. Although it would not directly prevent bycatch, reporting all recovered rings would allow scientists to more accurately define population-specific bycatch patterns in regional areas resulting in more targeted conservation efforts. The third recommendation is to implement regulations on fishing efforts in the waters surrounding Amsterdam Island during the austral winter. The combination of these three conservation efforts would allow the world’s only population of the Amsterdam albatross to grow and prevent any further decline that might very well result in the extinction of the species.

References:

Thiebot J.B., Delord K., Barbraud C.B., Marteau C., Wemerskirch H. 2015. 167 individuals versus millions of hooks: bycatch mitigation in longline fisheries underlies conservation of Amsterdam albatrosses. Aquatic Conservation: Marine and Freshwater Ecosystems. DOI: 10.1002/aqu.2578

Bioaccumulation of Toxins in Shellfish and the Consequences for Human Health

October 8, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By James Keegan, RJD Intern

Toxic shellfish and toxic seafood in general are not modern phenomena. Human practices and records indicate that shellfish poisoning has been around for hundreds if not thousands of years. Many believe that diet restrictions dictated by the Bible demonstrate a wariness of shellfish poisoning. Moreover, Native Americans would keep watch for the flickering of ocean waves, an indication of dinoflagellate abundance, in order to know when to stop eating shellfish (Williams et al. 1999). Dinoflagellates are tiny marine organisms ultimately responsible for shellfish toxicity as well as the infamous red tides. More recently, the first published description in the Western World of a patient with symptoms of shellfish poisoning dates back to 1689 (Williams et al. 1999). A more famous example may be the poisoning of Captain Vancouver’s crew in British Columbia, Canada, in 1793 after they consumed toxic mussels (Landsberg 2002).

Bioluminescent dinoflagellates lighting a breaking wave. Image source: Wikimedia Commons

Today, doctors recognize that the ingestion of shellfish can cause several types of neurologic diseases. These diseases include shellfish poisoning, diarrheal shellfish poisoning, and neurotoxic shellfish poisoning, but paralytic shellfish poisoning is one of the most common (Williams et al. 1999). Commonly implicated varieties of shellfish include mussels, clams, oysters, and scallops. Paralytic shellfish poisoning is caused by saxitoxin found in certain shellfish (Williams et al. 1999). Because saxitoxin is heat stable, steaming and cooking do not affect its potency, so both raw and cooked shellfish can cause paralysis. Moreover, commercial processing does not eliminate the toxin. The onset of symptoms of paralytic shellfish poisoning is rapid, occurring within 30-60 minutes of ingestion. Victims complain of a feeling of pins and needles, numbness, vertigo, and tingling of the face, tongue, and lips. There are no antidotes for saxitoxin or paralytic shellfish poisoning; however, even patients with severe symptoms do well if quickly supported by respiratory systems (Williams et al. 1999).

Although shellfish contain the toxins that cause these neurological diseases, they do not produce them. Instead, these toxins come from toxic microalgae like dinoflagellates. They serve as food for the shellfish, which filter and concentrate them in digestive glands (Williams et al. 1999). Because shellfish filter feed, they can take up toxic cells from these microalgae directly from the water column (Landsberg 2002). Shellfish then store and accumulate toxins as they feed on microalgae, and these accumulated toxins can become harmful to consumers once ingested. Shellfish naturally ingest a variety of dinoflagellate species, so their toxin profiles vary depending on the toxicity of the dinoflagellate to which each population is exposed. Many toxic microalgae have sedimentary or resting stages as part of their life cycle, and in some cases, these stages may be more toxic than the floating planktonic ones. These stages can be up to 1000 times more toxic, so shellfish filtering sediments can be exposed to much higher levels of toxins (Landsberg 2002). Moreover, the location and concentration of toxins in various tissues varies between species. For example, scallops do not accumulate toxins in their adductor muscles, the only part usually consumed, so they are normally safe for public consumption (Landsberg 2002).

A pile of clams. Image source: Wikimedia Commons

Although toxins are widely distributed among shellfish, generally long-term toxin deposition had not seemed to cause them adverse health effects. However, in recent years, researchers have begun to focus on the effect toxins have on shellfish and found that they may indeed harm or even kill shellfish (Landsberg 2002). This assertion gains credibility as several studies have shown that shellfish behaviorally avoid the consumption of toxic dinoflagellates (Landsberg 2002). Examples of this would be closing shells, reducing pumping and filtration rates, increasing mucus production, modifying burrowing behavior, and changing cardiac activity or oxygen consumption (Landsberg 2002). Therefore, the accumulation of toxins in shellfish has health consequences for both the shellfish themselves and the animals higher up on the food chain.

The most effective way of managing shellfish poisoning is prevention. For centuries, humans have recognized that toxic seafood coincides with certain seasons of the year, water temperatures, weather conditions, seabird mortality, and the color of the waves (Williams et al. 1999). These methods are not exact, so monitoring programs use more modern techniques when determining potential shellfish toxicity. Programs have recently used mice to monitor toxin levels in shellfish by extracting their accumulated toxins and injecting them into the mice (Williams et al. 1999). Low concentrations may have little effect while high concentrations will kill the mice. Although effective, scientists would like to find a more rapid and direct method to monitor potential shellfish toxicity that does not require the use of mice. Scholin et al. 1999 developed a method to monitor microalgae, the ultimate source for shellfish toxicity, and their concnetrations. A floating robotic instrument will take in seawater and break apart any floating cells. It will then recognize certain microalgae by the presence of their DNA and relay this information to monitoring stations onshore. This system is still not completely ready, but it promises a much faster reaction time to fluctuating levels of microalgae.

The MBARI-designed robotic instrument called the Environmental Sample Processor. Image source: NOAA.gov

Modern coastal monitoring agencies have decreased incidence of shellfish poisoning by restricting shellfish harvesting during high-risk periods, such as the period from late spring to early fall (Williams et al. 1999). Recent outbreaks of shellfish poisoning have occurred on isolated islands where public health monitoring is infrequent (Williams et al. 1999). Accumulated toxins cause illness in people, but only with elevated levels during certain periods of time. With vigilant surveillance, consumption of shellfish does not pose a significant health risk to humans.

References:

Clark, RF, SR Williams, SP Nordt, AS Manoguerra. (1999) A review of selected seafood poisonings. Undersea & hyperbaric medicine 26:3, 175–184.

Landsberg, Jan H. (2002) The Effects of Harmful Algal Blooms on Aquatic Organisms, Reviews in Fisheries Science 10:2, 113-390, doi: 10.1080/20026491051695

Scholin, C. A., R. Marin III, P. E. Miller, G. J. Doucette, C. L. Powell, P. Haydock, J. How- ard and J. Ray. (1999) DNA probes and a receptor binding assay for detection of Pseudo-nitzschia (Bacillariophyceae) species and domoic acid activity in cultured and natural samples. Journal of Phycology 35:1356–1367

Modeling for Management: Predicting Ideal Conditions for Seagrass Habitat

October 6, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By Emily Rose Nelson, RJD Intern

Seagrasses are an essential part of the marine ecosystem. They provide food, habitat, and safe nursery areas to a wide range of species. Seagrasses help to stabilize the sea floor during intense currents and storms, filter nutrients coming from land-based runoff, increase water clarity by trapping sediments, generate oxygen, and store excess carbon. Unfortunately, seagrass area is in significant decline around the world largely due to cumulative impacts of human activities such as coastal development, increasing pollution, and reckless boating. It is of utter importance that conservation and restoration efforts are put into place in order to protect seagrasses the ecosystem services they provide.

Map showing changing in seagrass area since 1879 at 205 sites along coastlines worldwide (Waycott et al., 2009).

To date, restoration efforts have been largely unsuccessful. In order to effectively reestablish seagrass area, knowledge of the environmental factors that impact seagrass is necessary. Presence requires a number of environmental conditions including light availability, wave height, and sediment characteristics to be satisfied. Knowing this, Adams et al. have created a mathematical model to link environmental conditions to the presence or absence of seagrass.

Moreton Bay, Australia is subtropical shallow coastal embayment. There is decades of extensive data on seagrass cover and environmental conditions available for this area, making it the perfect location to use to develop this model. The model takes into account three of the most important factors in the success of seagrass: light levels (represented by mean annual benthic light availability), physical wave conditions (represented by significant wave height), and geological sediment conditions (represented by mud concentration). Looking at previous data and performing a number of mathematical manipulations established limitations for each of the three environmental factors. Seagrass will only be present when the following conditions are satisfied: annual benthic light availability is greater than 9molm^-2d^-1, mean significant wave height is less than 0.6m, and sediment mud concentration is less than 50%. The study area was then divided into 100m by 100m cells and the presence or absence of seagrass was tested for each cell using the mathematical model.

Application of the model to Moreton Bay, Australia provided promising results. When compared to a real seagrass map from 2004, the model correctly predicted seagrass presence or absences at 85% of the cells. The model did even better when compared to a real seagrass map from 2011, correctly predicting 88% of the cells. Further, it is possible that some of the incorrect cells, in particular false positives, correspond to areas of opportunity for future seagrass growth.

Real seagrass observational data compared to predictions using the model developed by Adams et al. for 2004 and 2011. a, b, and c are based on seagrass observed in 2004 and d, e, and f are based on seagrass observed in 2011. a/d show the observed seagrass data, b/e show the predicted seagrass using the model, and c/f show the difference between the real observations and the model predictions.

The success of the model created by Adams et al. provides hope for combining continual monitoring with modeling as a method to determine actions needed for conservation and restoration of seagrass beds on a local level. The limiting environmental factors differ among locations and therefore different actions are needed to improve chances of seagrass survival; if the model predicts absence of seagrass at a particular spot there is an environmental reason for that. If the area does not have enough sunlight efforts should be made to improve water clarity, and thus allow more light through. If the area has intense wave conditions, actions can be put in place to weaken the physical effects of waves. Knowing a specific reason why seagrass is absent in a particular area makes it easier for policy makers to successfully manage the area.

A school of yellow striped grunt swimming through the seagrass (photo credit: google images).

However, there are fallbacks to this model. For one, there are several other environmental variables that effect seagrass that are not taken into account. The model also does not account for interactions between seagrass abundance and the environmental conditions. It is also important to consider that management decisions, such as adding a break wall to minimize wave action, will likely affect other environmental factors indirectly. Despite some issues with this model, it does provide a start. Further work, such as adding additional environmental variables to the model, has the potential to make modeling an effective tool for restoration and conservation of seagrasses.

Reference:

Adams, M. P., Saunders , M. I., Maxwell, P. S., Tuazon , D., Roelfsema, C. M., Callaghan, D. P., et al. (2015). Prioritizing localized management actions for seagrass conservation and restoration using a species distribution model. Aquatic Conservation: Marine and Freshwater Ecosystems.

Waycott, M., Duarte, C.M., Carruthers, T.J.B., Orth, R.J., Dennison, W.C., Olyarnik, S., et al. (2009). Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proceedings of the National Academy of Sciences of the Unites States of America.

Competitive Interactions Between South American Sea Lions and Fishermen in Southern Brazil

October 1, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By James Keegan, RJD Intern

Often, humans and top predatory carnivores compete for the same resources, even in the marine environment. This conflict occurs where fishing operations of humans and feeding areas of the predators overlap. In South America, fishermen complain of adverse competition from South American sea lions, which interact with all types of fishing gear. South American sea lions can interact with fishing effort either directly or indirectly. They can damage the fish captured by nets or the nets themselves, or they can decrease the relative abundance of local fish, decreasing the fishermen’s yield. Conversely, this competition can adversely affect the sea lions, decreasing their populations or changing their diet composition. Machado et al. 2015 sought to understand the competitive influence between humans and South American sea lions by providing the first detailed characterization of direct interactions between coastal gillnet fishing and the sea lions in Brazil.

Off the coast of southern Brazil, medium-scale gillnet fishing is the predominant fishing activity. Gillnets are vertical panels of netting hanging in the water column which allow fish to pass their heads through the netting, but not their bodies. The net then snags onto the fish’s gills as they try and back out, capturing the fish. Gillnet fishing activity in this region was monitored during three periods: 1992 to 1998, 2003 to 2005, and 2011 to 2012. During the surveys, scientists collected vessel characteristics, fishing area and net location gear type, target species, fishing effort (length of the nets and soak time), number of fishing operations (recovery of the net from the water), fish species captured, and the number of South American sea lions present near a net during a fishing operation.

Study area showing two fishing harbors (Imbé and Passo de Torres) in Southern Brazil. The gray circles represent fishing operations based out of Imbé and the gray triangles represent fishing operations based out of Passo de Torres. (Machado et al. 2015)

Machado et al. 2015 found that South American sea lions interacted with gillnets in 24% of the fishing operations monitored. They also found that interactions increased with increased soak time, and that interactions were significantly affected by the seasons, with more interactions occurring in the winter. Moreover, in 85.3% of the interactions recorded, South American sea lions ate fish caught in the nets. In order to trick or drive the sea lions away, fisherman would resort to tactics like throwing fireworks in the water or putting out decoy nets. Fortunately, no sea lion mortalities occurred during the study due to incidental capture or injury caused by fishermen.

Relative frequency of occurrence of interactions between South American sea lions and coastal gillnet fishing in the two study areas of Imbé and Passo de Torres in southern Brazil during the three study periods (1992-2012). (Machado et al. 2015)

The highest frequency of interactions occurred in autumn and winter. This may be due to the low fish availability during that time, requiring a greater effort from the sea lions to obtain food, which creates a driving force for targeting fishing vessels. However, these interactions seem not to have a great economic impact on fisheries because they do not occur at a high frequency throughout the year, and the amount of fish the South American sea lions consume represents about .8 to 3.5% of the total landed value of the catch (Machado et al. 2015). Nevertheless, South American fishermen have a negative view of the sea lions, saying that they cause a significant economic loss. Moreover, this negative perception will only worsen in the future as fish stocks continue to decrease and competition for this resource increases. In order to alter this perception, a fisheries management system needs to be developed that reduces fishing effort and recovers fish stock. Additionally, by educating fishermen on the real economic impact sea lions have on their production, conflicts between fishermen and sea lions would decrease.

References:

Machado, R., Henrique, P., Benites Moreno, I., Danilewicz, Tavares, M., Alberto Crespo, E., Siciliano, S., Rosa De Oliveira, L. (2015). Operational interactions between South American sea lions and gillnet fishing in southern Brazil. Aquatic Conservation: Marine and Freshwater Ecosystems. doi: 10.1002/aqc.2554

Masked, diluted and drowned out: how global seafood trade weakens signals from marine ecosystems

September 29, 2015/0 Comments/in Conservation, Ocean News /by aanstett

By Jake Jerome, RJD Graduate Student

It has been shown that global seafood trade inherently drives seafood production, negatively impacting marine ecosystems worldwide. While it is well known that these ecosystems are deteriorating, most research has been focused on global stock assessments, catch trends, or fisheries dynamics, with little attention given to researching the ways in which global trends are linked to consumers through trade. Fish prices can potentially be used as a feedback signal to consumers about the state of fisheries and marine ecosystems, but this method faces several issues. Crona et al 2015 dive deeper into the usefulness of using fish prices as a feedback signal, but develop a set of mechanisms that combine to weaken this signal from global trade to consumers.

The first mechanism that weakens price signals is masking. Masking occurs within individual fisheries and consists of two parts. First, negative impacts that arise from fishing are often separated from the operating cost of the fishery. For example, fisheries may cause habitat destruction or result in bycatch of endangered animals, but neither of these have a large impact on the yield or cost. Second, short-term catch trends may not provide accurate representation of target stock declines due to factors such as increased effort, technological advances, and fishing deeper or farther from shore.

Shrimp trawl net with bycatch (Elliott Norse, Marine Conservation Institute/Marine Photobank)

The second mechanism discussed is dilution. Dilution occurs when the amount of supply that an individual fishery has declines but is hidden from consumers by using the supply from another resource area. For example, the UK imports Atlantic cod from Iceland and Faeroes to make up for the decline of North Sea cod. Through dilution, changes in any one ecosystem are concealed from consumers because substitutable products are made available from different ecosystems.

A third mechanism examined is the ‘drowning out’ of price signals. This is usually due to other market factors that affect fish prices. Things like changes in consumer spending patterns or price/availability of alternative protein sources can combine to alter fish prices that do not necessarily connect with ecosystem or species decline.

Chilean Seabass for sale at Whole Foods (Gerick Bergsma 2011/Marine Photobank)

In conclusion, the authors suggest that the feedback from individual fisheries to consumers worldwide is highly asymmetric and that price signals reflecting changes in the source ecosystem typically are masked, diluted, or drowned out unless large proportions of seafood stocks collapse. Despite this, opportunities do exist that possibly could help provide a positive feedback signal to consumers, resulting in promoting sustainable seafood practices.

Source: Crona, B. I., Daw, T. M., Swartz, W., Norström, A. V., Nyström, M., Thyresson, M., Folke, C., Hentati-Sundberg, J., Österblom, H., Deutsch, L. and Troell, M. (2015), Masked, diluted and drowned out: how global seafood trade weakens signals from marine ecosystems. Fish and Fisheries. doi: 10.1111/faf.12109