Ocean News – Page 29 – Shark Research & Conservation Program (SRC)

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.

Shark Tagging in West Palm Beach with American Heritage Academy

November 4, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Emily Rose Nelson, RJD Intern

I had been trapped in my office, with no sight of the ocean for over a month. If this trip had been one day later I might have gone crazy, I needed to get out on the water. That being said, I was even more excited than usual to go shark tagging. We met at RSMAS bright and early to load gear and somehow managed to fit all of our gear plus 4 people into my car. Before even leaving RSMAS I found barracuda scales in my hair, a sure sign that it was going to be a good day.

After an easy drive and an obligatory stop at the nearest Starbucks the team arrived at the dock in West Palm. This was only the second day trip we had run with Jim Abernethy’s Scuba Adventures (RJD runs a research expedition in the Bahamas to “Tiger Beach” with JASA) and we were eager to check out the new fishing site. After loading gear with the help of our guests for the day, American Heritage Academy, we were off.

The RJD team preps gear for a day of shark tagging.

The conditions were perfect; the ocean was flat calm and their wasn’t a cloud in the sky. We set all 30 lines and throughout the day did not pull up a single shark. However, everyone was still in high spirits. It was a beautiful day and we had time for a couple swimming breaks. We even had the chance to see a Loggerhead Sea Turtle swimming by. We set 6 additional lines with hopes that we would get lucky at the end.

On the 33^rd line of the day someone yelled what we had been waiting to hear all day, “tension!” The RJD team waited in anticipation to confirm that there was a shark on the line and suddenly it surfaced. My all time favorite, a beautiful, juvenile tiger shark was on the end of the line. As we pulled her up it quickly became clear that she was a strong girl. After a couple of attempts, we safely restrained her on the platform in order to perform a quick work up. One of my favorite moments of the day was helping one of the high school students place a dart tag in the shark. It was his first time on a boat and excitement was pouring out of him. After we collected all the data from her, we safely released the shark and she swam off in excellent condition.

Removing the pump from the tiger shark in order to safely release it back into the ocean.

As we headed back to dock the RJD team started to clean up, feeling satisfied with the day. However, the fun was not over yet. A group of dolphins decided to hitch a ride with us. They were jumping and playing at the bow of the boat for quite some time. While I am not much of a “dolphin person” I can’t help but smile whenever this happens, it was the perfect way to end a great day on the water!

Global population growth, wild fish stocks, and the future of aquaculture

October 28, 2014/2 Comments/in Conservation, Ocean News /by aanstett

By: Hannah Calich, RJD Graduate Student

For many years we lived in a world where the state of our fish stocks was not a primary concern. However, our population has become so large, and our technology so advanced, that we are utilizing resources at a rate that was once inconceivable. We have significantly impacted many of the world’s fish stocks and it is no longer biologically or economically feasible to continue harvesting them at this rate. Thus, we must develop ways to relieve pressure on wild fish stocks while continuing to provide the world with the fish protein it requires. Given the projected human population, and the current status of wild fish stocks, it will be up to the aquaculture industry to help the ocean meet the world’s demand for fish protein.

The global human population has been projected to reach over 9 billion people by 2050, and over 10 billion people by 2100 (Figure 1; UN, 2012). While the rate of population growth has been slowing, and may eventually reach a plateau, feeding a population of 9 to 10 billion people represents a significant challenge.

Projected world population based on a medium population growth variant (data from UN, 2012)

Along with the world’s population, meat consumption has been steadily rising. In the 1950s the world’s population was consuming 44 million tonnes annually; by 2009 that figure had increased to 272 million tonnes. When the increase in human population is taken into consideration those figures suggest that the annual per capita meat consumption rate has more than doubled, to almost 90 pounds per person (Brown, 2011).

While on average the world’s meat consumption has been rising, there are regional trends in who can afford to eat meat. As Brown (2011) said, “wherever incomes rise, so does meat consumption” (pg. 173). As a result of incomplete or insufficient diets, currently 800 million people suffer from chronic malnourishment worldwide (FAO, 2014).

Fish are an important source of protein, nutrients and energy, particularly in poorer nations where essential nutrients are often scarce (FAO, 2014). For example, 150 g of fish protein can provide 50-60% of an adult’s daily protein requirement (FAO, 2014). In addition to being nutritious, fish are often an affordable source of protein. As such, nearly 17% of the global population’s protein intake comes from fish, though again the trends are regional and that number is closer to 50% for some developing countries in Africa and Asia (FAO, 2014). Following the trend of the world’s meat consumption, per capita fish consumption as also increased, from 10 kg in the 1960s to over 19 kg in 2012 (FAO, 2014). Per capita fish consumption has increased in both developing regions (5.2 kg in 1962 to 17.8 kg in 2010) and low-income food-deficit areas (4.9 kg to 10.9 kg) (FAO, 2014). While developed nations still consume more fish, the gap is narrowing.

The surge in fish consumption has left the marine capture industry struggling to meet the world’s demand for fish protein. Global marine capture fisheries have been consistently harvesting between 80 and 90 million tonnes per year since the mid-1980s (Figure 2; FAO, 2014; Pauly & Froese, 2012). However, this stability is not due to stable fish populations. Instead, the stability is due to pushing the boundaries of the ocean’s fish stocks. Specifically, the marine capture industry has been targeting less desirable species, fishing further offshore, and harvesting smaller fish than ever before.

Aquaculture and capture fisheries production in millions of tonnes from 1950-2012 (Source: FAO, 2014)

This high demand for fish protein has put a significant strain on wild fish populations. Currently, approximately 30% of wild stocks are considered overfished, 60% are fished at (or close to) their maximum sustainable limit, and only 10% are being fished under their limit (FAO, 2014). Overfishing not only negatively impacts the ecosystem, but also reduces fish production and has negative social and economic consequences. For example, in areas of poor governance fishers that are unable to legally catch their quotas occasionally turn to illegal, unregulated or unreported fishing techniques to earn a living. These practices can be wasteful, dangerous and negatively impact communities and the environment (FAO, 2014). Simply put, the world’s oceans cannot continue to support the planet’s increasing demand for fish.

Aquaculture has the potential to be the solution to the world’s fish shortage. Global aquaculture production is one of the fastest growing food-producing sectors. In 2012 aquaculture provided almost 50% of all fish for human consumption and has been predicted to provide 62% by 2030 (Figure 2; FAO, 2014). Not only are we raising more fish, but we are also eating more of the fish we raise. The amount of fisheries production used by humans for food has increased from about 70% in the 1980s to move than 85% (136 million tonnes) in 2012 (FAO, 2014). In fact, in 2012 aquaculture production was higher than beef production (66 million tonnes compared to 63 million tonnes) (Larsen & Roney, 2013). This increase in productivity is largely due to an increase in small-scale fish farms (FAO, 2014).

In addition to helping feed the world, aquaculture can play a critical role in the economy. Together, the fisheries and aquaculture industries help support the livelihoods of 10-12% of the world’s population (FAO, 2014). Additionally, fish is one the most commonly traded commodities worldwide and was worth almost 130 billion dollars in 2012; a value that has been predicted to increase into the future. The fish trade is particularly important in developing nations where in some cases the trade is worth over half of the total value of traded commodities. Aquaculture also benefits to the economy because of how efficiently herbivorous fish convert feed into live weight. For comparison, the grain to live weight ratio of cattle is approximately 7:1, it is 4:1 for pork, 2:1 for chicken and less than 2:1 for herbivorous fish such as tilapia or catfish (Brown, 2006). Since herbivorous fish have such a low ratio, focusing on them will allow us to harvest more protein while using less grain.

Aquaculture, in addition to directly providing food, can also serve as a way to support and replenish natural fish stocks. For example, in 2011 the Mississippi Department of Natural Resources raised and released 7,500 cobia in the northern Gulf of Mexico. The project’s aim was to help replenish stocks and to examine the feasibility of releasing fish that were raised in aquaculture facilities into the wild as part of a stock enhancement program (Mississippi Department of Natural Resources, 2011).

While aquaculture has shown great promise, like any industry it has it’s flaws. Two of the primary environmental concerns with aquaculture are preventing ecosystem degradation, and raising carnivorous fish without harming prey populations. Ecosystem degradation comes in many forms but can include: habitat destruction, disease, pollution, and changes to a species’ population genetics. Raising carnivorous fish, such as salmon or tuna, is controversial because while they are economically important species, their growth depends on the availability of large quantities of small prey fish, such as pilchards. Harvesting large quantities of wild prey fish for fish meal can seriously impact the prey’s natural populations (Brown, 2006). To continue to grow sustainably the aquaculture industry needs to reduce its environmental impact as well as become less dependent on wild fish for feed, and increase the diversity of culture species.

While there are important sustainability concerns surrounding the aquaculture industry, the industry is progressing and adapting at a very fast rate and fortunately, these concerns are becoming less relevant. Since the world’s population is only predicted to increase, finding a way to meet the world’s demand for fish without relying on wild stocks is essential. So long as the aquaculture industry continues to develop in a way that is environmentally sustainable, aquaculture will have an important role to play in providing healthy fish protein and jobs for the world’s economy.

References:

Brown, L. R. (2006). Plan B 2.0: Rescuing a Planet Under Stress and a Civilization in Trouble. Washington, DC: Earth Policy Institute. Retrieved September 4, 2014 from http://www.earth-policy.org/books/pb2

Brown, L. R. (2011). World on The Edge. Washington, DC: Earth Policy Institute. Retrieved September 4, 2014 from http://www.earth-policy.org/images/uploads/

book_files/wotebook.pdf

FAO. (2014). The State of World Fisheries and Aquaculture 2014. Retrieved September 4, 2014 from http://www.fao.org/3/a-i3720e.pdf

Larsen, J., & Roney, M. (2013). Farmed Fish Production Overtakes Beef. Retrieved September 4, 2014 from http://www.earth-policy.org/plan_b_updates/2013/ update114

Pauly, D., & Froese, R. (2012). Comments on FAO’s State of Fisheries and Aquaculture, or ‘SOFIA 2010’. Marine Policy, 36(3), 746-752.

Mississippi Department of Marine Resources. (2011). Cobia Released on Popular Mississippi Offshore Artificial Reef. Retrieved September 4, 2014 from http://www.dmr.state.ms.us/index.php/news-a-events/recent-news/272-11-131-lst

UN. (2012). World Population Prospects: The 2012 Revision. Retrieved September 4, 2014 from http://esa.un.org/unpd/wpp/unpp/panel_population.htm

Early Life History Predator-Prey Interactions and Habitat Use of the American Eel and American Conger

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

By Alison Enchelmaier, RJD Graduate Student

Declines in the American eel, Anguilla rostrata, have raised interest in studying the species’ early life history. Potential causes could include overfishing, increased predation, and habitat loss; but determining the cause is difficult due to the American eel’s complex life history. One potential factor, predation, is important to consider as the refuge value of estuarine nursery habitats are being reevaluated (Musumeci et al., 2014).Another factor is habitat competition. American eels arrive in North Atlantic estuaries in their early juvenile stage called glass eels, from the winter to spring. This overlaps with another species called Conger oceanicus. Commonly called the American conger, this species arrives in estuaries in the spring to summer. Considering both species have similar life histories, overlapping arrival to estuaries, and the American conger is a piscavore it is possible that both species compete for habitat space and C. oceanicus may prey on A. rostrata (Musumeci et al., 2014).

Early juvenile stage of eel growth called glass eels. Photo credit: http://www.caryinstitute.org/students/hudson-data-jam-competition/data-jam-data-sets/eels-hudson-river-tributaries-nysdec

Musumeci et al. (2014) examined the habitat use of both American congers and American eels by placing them in bowls containing sand and PVC pipe shelter. Each eel was observed to see how often they buried themselves in the sand, rested on top of the sand, or sheltered in the PVC pipe. American eels spent nearly even time sheltered (39%), buried (30%), and on top of the sand (31%). Alternatively, American congers divided their time lying on top of the sand (52%) and sheltering (48%). No congers buried themselves in the sand (Musumeci et al., 2014). From these observations it appears that there is some overlap in both species habitat use, though only American eels bury themselves.

To examine predator-prey relationships, Musumeci et al. (2014) placed two eels of varying sizes together for 24 hours. Predator-prey pairs were one American conger and one American eel, two American congers, or two American eels. American congers successfully preyed on American eels in 45% of the trials. American congers did not seem to have a size preference, as they preyed on American eels of similar and smaller sizes. American eels did not prey on American congers in any of the trials. When two congers were paired together cannibalism occurred in 16% of the trials, usually when the eels were different sizes. Only 1% (one instance) of American eel trials resulted in cannibalism.

Predator-prey interaction between an American conger (larger, predator) and American eel (smaller, prey). Photo credit: Musumeci et al., 2014)

Interactions between American congers and American eels are likely as they have been collected together for several decades. Both species arrival to estuaries and habitat preferences overlap, which means that they may compete for habitat space and demonstrate predator-prey interactions (Musumeci et al., 2014). Based on predation trials, it appears that American eels are potential prey for American congers, which has not yet been observed in nature. American conger cannibalism was frequent enough to indicate that it may occur in nature, though it has not yet been observed in field. The lack of American eel cannibalism contradicts culture system observations of cannibalism between similarly sized juveniles (Musumeci et al., 2014).American conger predation on American eels may affect the American eel’s survival and habitat use. This new information shows that predation and habitat space competition could play a part in the American eel’s decline.

Reference: Musumeci, V.L., Able, K.W., Sullivan, M.C., & Smith, J.M. (2014). Estuarine predator—prey interactions in the early life history of two eels (Anguilla rostrata and Conger oceanicus). Environmental Biology of Fishes. First published online: 1 November 2013.

Evidence for collective navigation in salmon for homeward migration

October 21, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Hanover Matz, RJD Intern

The long migrations undertaken by Atlantic and Pacific salmon to reach their spawning grounds are known by many. Salmon are anadromous; they spend their adult lives foraging at sea, and then return to the freshwater rivers of their births to spawn and reproduce. How this remarkable feat is accomplished by the salmon with such accuracy is believed to be a combination of geomagnetic and olfactory cues. However, Berdahl et al. examined evidence that salmon may also be relying on social interactions and collective behavior in order to navigate to their natal homes. The authors hypothesized that salmon migrating in large groups could more accurately navigate to their spawning grounds by reducing the effect of navigational errors made by individual salmon. In order to determine whether this was the case, Berdahl et al. compiled results from previous studies that indicated a decrease in straying with an increase in abundance, proposed potential benefits of collective navigation for salmon, and used catch size data to better understand how salmon aggregate in the wild.

The basis for collective navigation in migrating animals is that by traveling in relatively large groups, animals can reduce the effect of navigational errors made by individuals in the group by distributing those errors across the decisions of the group as a whole. A school of salmon returning to their home river can more accurately find that river by relying on the collective decisions of the group rather than an individual salmon can by reading cues on its own. Berdahl et al. synthesized results from multiple studies that showed salmon more effectively returned to their natal grounds when they were in higher abundance, indicating the possible role of collective behavior. Figure 1 shows the results taken from several studies, all of which demonstrate that as the run size or abundance of salmon increased, the straying rate of salmon migrating back to their natal rivers decreased. The more salmon present, the less likely individual salmon were to stray from the correct migration path, suggesting the possible role of collective navigation.

Results of several studies indicating a negative relationship between straying rate and run size in salmon

With this evidence for collective navigation in mind, the authors postulate several potential benefits to salmon through such behavior. Not only would collective navigation allow schools of salmon to properly orient themselves when traveling from the high seas to coastal environments, but it would also allow them to pinpoint the proper estuaries and river mouths necessary to reach their natal grounds. When presented with multiple rivers to migrate towards, collective navigation would also allow the group to effectively decide on the correct path, rather than relying only on the abilities of the individual fish. By making orientation and migration decisions based on the collective choices of the group, the salmon can reduce the effect of errors made by individual fish and the school can reach their spawning grounds based on the decisions of only a few informed individuals. Schooling offers many other potential benefits besides collective navigation, such as protection from predators, and it is likely that salmon rely on both visual and pheromone cues in order to migrate as a group. In order to further provide evidence for collective navigation in salmon, the authors collected catch size data to determine the degree to which salmon school in the high seas. The data revealed that the catch sizes for multiple species varied from the expected Poisson distribution, indicating the salmon likely aggregate in the open sea. It was overall rare to find fish, and when they were found, they were often found in large numbers, suggesting a degree of schooling at sea. This schooling may increase with increasing migratory behavior. Figure 2 shows the results of the catch size data.

Catch size data for multiple salmon species, shown in solid lines, does not follow the expected Poisson distributions, shown in dashed lines, indicating aggregation of the salmon

What does this evidence for collective navigation indicate? The possibility that salmon may rely on collective navigation in order to reach their spawning grounds implies that populations require enough individuals to aggregate and migrate as a group. What this means for salmon fisheries is that even if a fishery is managed to allow for the future reproduction of the salmon, if enough individuals are removed from the fishery so that the remaining fish cannot effectively aggregate, they may not be able to reach their natal rivers to reproduce. The population may be numerically fished so that there are enough individuals remaining to continue reproducing, but they may be distributed in such a way that they cannot school in large enough numbers to migrate. This could potentially lead to detrimental overfishing of salmon stocks. In order to fully understand the degree that social interactions may play in salmon migration and reproduction, future studies will have to be conducted on the role of collective navigation in salmon and other organisms that migrate over long distances.

References

1. Berdahl, A., Westley, P. A., Levin, S. A., Couzin, I. D., and Quinn, T. P. 2014. A collective navigation hypothesis for homeward migration in anadromous salmonids. Fish and Fisheries.

Maltreatment as hatchlings predisposes Nazca boobies to more frequent violent episodes as adults

October 17, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Daniela Escontrela, RJD Intern

The Galapagos Islands are home to four species of native and endemic boobies: the blue footed boobies, the masked boobies, the Nazca boobies and the red footed boobies. The name for the boobies comes from the name “bobo” which is a Spanish term for fool or clown. They are all part of the Gannet family which is also found in North America. These birds have dagger like beaks and are accustomed to diving into the ocean for their food. Although the three species of boobies nest and breed in approximately the same territories they don’t fish near each other. The blue footed boobies feed close to shore, the masked boobies farther out and the red footed boobies even farther out. The masked booby is the biggest of all the boobies; they are mostly white colored with black tail feathers and black primary feathers at the end of their wings. They have a yellow beak, with the females sporting a paler beak than the males. The term “masked” booby comes from the black skin at the base of their beak that makes it look like they are wearing a mask. Although the masked booby feeds itself by plunge diving, like the other boobies, this is rarely observed as it feeds farther offshore. These birds breed on an annual cycle, but each island has their own times for breeding. Like the other boobies, they have courtship rituals and dances but they are far less intricate than those of the blue footed boobies. The masked booby will lay two eggs but only one of them will hatch and be reared by the parents. These birds can often be found laying eggs on the islands of Espanola, San Cristobal and Genovesa. (Fitter et al 2000).

An image of a Nazca booby at Roca Union near the island of Isabela, Galapagos. Photo by Daniela Escontrela

The Nazca booby, which is native to the Galapagos, is a separate species than the masked booby but they are closely related and share a lot of the same characteristics and behaviors. Nazca boobies when young experience two types of maltreatment or violence: obligate siblicide and interactions with non-parental adult visitors. The cycle of violence hypothesis which has been tested on human subjects states that child abuse may be a cause violent behavior later in life. Nazca boobies provide a non-human model to test these hypothesis as the chicks are often subject to abuse, either from siblings or from nonfamilial adults. (Muller et al, 2011) Using the cycle of violence hypothesis, we predict that Nazca booby chicks subjected to these types of interactions may be more predisposed as adults to engage in similar aggressive activities, such as becoming non-parental adult visitors themselves. Furthermore, we predict that the predisposition of violent episodes experienced by adult Nazca boobies may be correlated with increased amounts of hormone release.

Nazca boobies vary in the size of the clutch they lay and it has been found that clutch size can often be related to the female’s food limitation (Humphries et al, 2005). The only reason the original clutch size may exceed more than one egg is because the second egg provides an insurance in case the first egg fails to hatch (Ferree et al, 2004). However, even though boobies often lay two or more eggs, usually only one of the chicks makes it to independence. The reason for this is that Nazca boobies practice a behavior termed obligate siblicide where aggression from a core chick often causes the mortality of the marginal chick which results in a brood reduction. (Humphries et al, 2005). Siblicide is often described as a form of a lethal attack coming from a sibling; if both eggs hatch, one chick will kill the other usually by pushing it off the nest. Once pushed off, the chick usually dies due to starvation, exposure or predation. Rarely does the chick make it back to the nest. (Ferree et al, 2004) In a study, very rarely did two chicks from one clutch make it to independence because of obligate siblicide. In the few cases two chicks made it to independence, one of the chicks was usually in such poor condition it almost didn’t make it. (Humphries et al, 2005)

Another form of aggression or maltreatment Nazca booby chicks experience is interactions with non-parental adult visitors (NAVs). In this interaction, adults tend to show an attraction to offspring of other parents which is often sexually or aggressively motivated. (Muller et al, 2011). There seems to be no reward for the adults that engage in this behavior while the chicks can often be injured (Grace et al, 2011). In Nazca booby communities this aggression or attraction to other nonfamilial young is common and most adult boobies engage in these acts at least once in their life. Nazca boobies are often raised as solitary nestlings (because the other chick is usually killed by obligate siblicide) in dense colonies were there are large probabilities for these NAV interactions. (Muller et al, 2011) In fact most nestlings experience NAV interactions at least once during their nesting period (Grace et al, 2011). NAV events usually occur when chicks are between 30 and 80 days old and usually happen because the chicks are left unattended while the parents go out and forage for food. When unattended by the parent, nonbreeding adults will seek the chicks for social interactions. These NAV events are less common when parents are around because the parents will chase away these adults. (Muller et al 2011)

A non-parental adult visitor (NAV) exhibits aggressive behavior (Grace et al, 2011)

There has been a positive correlation between the number of attacks chicks received (either from siblings or other adults) and the number of times the same chick participated in NAV behavior as an adult. The attacks received by the chicks at early stages of life affect and mold individual personalities. Although the siblicide behavior is a strong predictor of adult behavior, NAV events tended to contribute more to molding individual adult behavior. This shows that experiences as chicks can mold adult social behavior (Muller et al 2011).

Testosterone is a hormone released to mediate aggression. Testosterone is usually released when the argenine vasotocin system is stimulated. However, release of this hormone can be energetically expensive, especially if it has to be up-regulated for long periods of time. For this reason, according to the challenge hypothesis, testosterone is up-regulated only during social challenges. These social challenges include sibling aggression and interactions with NAVs which can be seen as times of fighting. After a study was conducted, it was found that testosterone levels tended to increase in the chicks during times of attack by NAVs or siblings. The chick being attacked tended to have higher testosterone levels than the attacker. In the case of obligate siblicide, the marginal chicks were often found to have higher levels of testosterone, even during times of no attack, because the core chicks represented such a threat. (Ferree et al, 2004) Another hormone, corticosterone which is associated with stress responses, was increased five-fold during maltreatment episodes (Grace et al, 2011).

Maltreatment behavior as adults is still not really understood. So far, three hypothesis have been proposed for the increased frequency of attacks inquired by adult Nazca boobies. One of the hypothesis predicts that “maltreatment in early life causes long term neuroendocrine changes that underline later maltreatment tendencies”. During NAV events, the hypothalamic-pituitary-adrenal (HPA) axis response is induced in the nestling under attack. Repeated activation of the HPA axis may lead to long term endocrine changes which could carry on to adulthood. These acute changes in the HPA axis experienced by chicks induced during NAV episodes, if repeated often, may increase the chances that the individual will engage in more NAV behavior as an adult. In fact, adults engaging in NAV events have been found to have higher levels of circulating corticosterone and lower testosterone levels than those adults that are non-engaged in this behavior. These difference in hormone levels may be a result of repeated maltreatment events in early life which resulted in permanent neuroendocrine modifications. The other two hypothesis that may explain increased frequency of NAV behavior as adults is that the behavior is acquired through observational learning or that it is a genetically heritable trait. However, not much evidence or research has been done to prove these hypotheses so they must be ruled out until more research is performed. (Grace et al, 2011)

Nazca booby chicks experience obligate siblicide and NAV events in the early stages of their development. These events have been found to mold individual adult behavior; as a chick is exposed to more of either of the two events, the more likely the chick is to be involved in NAV interactions as an adult. As chicks are subjected to these maltreatment events, the HPA axis is also induced, causing changes in hormone levels. This repeated activation of the HPA axis as a chick may cause long term endocrine changes that can carry on to adulthood. These endocrine changes may be the underlying factor that cause these individuals to be more predisposed to engage in NAV events as adults.

References

Ferree, E. D., Wikelski, M. C., & Anderson, D. J. (2004). Hormonal Correlates of Siblicide in Nazca Boobies. Hormones and Behavior, 46, 655-662.

Fitter, J., Fitter, D., & Hosking, D. (200). Wildlife of the Galapagos. Princeton, New Jersey: Princeton University Press.

Grace, J. K., Dean, K., Ottinger, M. A., & Anderson, D. J. (2011). Hormonal effects of maltreatment in Nazca booby nestlings: implications for the “cycle of violence”. Hormones and Behavior, 60, 78-85.

Humphries, C. A., Arevalo, D., Fischer, K. N., & Anderson, D. J. (2005). Contributions of marginal offpsring to reproductive success of Nazca booby (Sula granti) parents: tests of multiple hypothesis. Behavioral Ecology, 147, 379-390.

Muller, M. S., Porter, E. T., Grace, J. K., Awkerman, J. A., Birchler, K., Gunderson, A. R., . . . Anderson, D. (2011). Maltreated nestlings exhibit correlated maltreatment as adults: evidence of a “cycle of violence” in Nazca boobies (Sula granti). The Auk, 1-19.

Economic vs. Conservation: Trade-offs between Catch, Bycatch, and Landed Value in the American Samoa Longline Fishery

October 14, 2014/0 Comments/in Conservation, Ocean News /by aanstett

By Laurel Zaima, RJD Undergraduate Intern

Commercial fisheries have prioritized maximum economic profit over the ecological distresses caused by their fishing practices. Consequently, unsustainable fishing practices hook high amounts of bycatch in relation to the amount of the target species. Bycatch are the animals that are accidentally caught and discarded due to lack of value, insufficient size, damaged, or regulatory reasons. Bycatch has detrimental effects on the populations of a diversity of marine species; therefore, has altered ecological relationships and the economics of commercial fisheries. A seemingly obvious solution to this threat would be the implementation of commercial fishing gear that mitigates bycatch. However, this resolution results in trade-offs among the catch, bycatch, and landed value. In their scientific research paper, Trade-offs among Catch, Bycatch, and Landed Value in the American Samoa Longline Fishery, Watson and Bigelow (2013) assess the benefits and disadvantages of modifying longlines to reduce bycatch in the American Samoa longline.

Longline fisheries often modify their fishing gear to the behavior characteristics of their target species in order to have the most catch per unit effort. Shallow hooks (<100 m) would be set to target yellowfin tuna and billfish, where as, deep hooks (>100 m) will be set to target albacore and bigeye tuna. The U.S. longline fishery based in American Samoa target a majority of their valued species in deep water, such as albacore. Unfortunately, their current fishing practices are not modeled after the behavior of their target species and have led them to catch tons of bycatch. Non-targeted species, such as green sea turtles, silky sharks, and oceanic whitetip sharks spend majority of their life near the surface, and are susceptible to longlines set in shallow waters (<100 m) or hooks passing through the surface during the setting or retrieval of hooks. The elimination of shallow water hooks or the redistribution of shallow hooks to deeper depths could help reduce bycatch and increase the landing of target species.

Watson and Bigelow (2013) modified the American Samoa fishery’s longline fishing gear by removing the shallowest hooks per section of the longline or by hypothetically redistributing the shallowest hooks to a deep position. In the first three scenarios, Watson and Bigelow (2013) eliminated the first hooks, the first and second hooks, and the first, second, and third hooks at both ends of each section. In the other three scenarios, the hooks were theoretically rearranged into deeper depths by extending the number of sections.

A Longline section has about 23-36 hooks between two floats, and each longline has up to ~100 sections. In Watson and Bigelow’s (2013) study, they modified the longline by either eliminating the shallowest hooks or by hypothetically reallocating them into deeper positions.

They found that there is a decrease in all catch, including a significant decrease in bycatch, by eliminating shallow hooks from longline sections. By reallocating the shallow hooks to deeper positions, there was an effective bycatch reduction while still sustaining target species landings. In terms of economic profit, it would be most beneficial for longline fisheries to redistribute their hooks to deeper positions because it increases their chances of catching the most valuable species. Specifically, there was an increase in catch of the three most valuable species in the American Samoa fishery, albacore, yellowfin, and bigeye tunas, with the redistribution of hooks. The increased catch of these 3 species alone would increase the total annual landed value by an estimated U.S. 1.4 million dollars.

In terms of conservation benefits, the removal of the first three shallow water hooks reduces bycatch for a variety of species, including 25 species of fish, sea turtles, billfishes, and some shark species. Although there are ecological advantages to the elimination or redistribution of the shallow water hooks, there are some economic trade-offs. In the scenarios of elimination and redistribution, there is a loss in landed value for wahoo, billfishes, and dolphinfish. However, the catch of tuna would probably compensate for the loss value of these species. There is also a possibility of an unintentional trophic cascade with decreased catches of billfish (tuna predators) because it could increase the predation on a fishery targeted tuna species. Another potential trade-off would be the increased bycatch of deeper dwelling vulnerable species, such as shortfin mako sharks and the bigeye thresher sharks.

A thresher shark is caught on a longline as bycatch.

Watson and Bigelow’s (2013) modifications to the hook distribution on longlines should be considered for implementation by longline fisheries that target deeper residing species. Depending on the location of the fishery, these longlines could have varying economic and ecological results. Nonetheless, adjusting the longline hooks to specifically target a species is the most feasbile way to reduce bycatch while sustaining target species catches.