Shark Tagging in West Palm Beach with American Heritage Academy

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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.

Photo 1 (1)

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 33rd 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.

Photo 2

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

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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.

calich 1

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.

calich 2

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

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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).

Figure 1 (1)

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.

Figure 2 (1)

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

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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.

Figure 1 salmon paper (1)

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.

Figure 2 salmon paper (1)

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

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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).

Figure 1 Nazaca Booby Paper

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)

Figure 2 Nazca Booby Paper

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

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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.

Picture 1

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.

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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.

Real-Time Spatial Management as a Bycatch Mitigation Measure

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By Hannah Calich, RJD Graduate Student

Bycatch, or the unintentional capture of non-target species, has negative biological, economical and social consequences (figure 1). Reducing bycatch has been a fisheries management priority in the US for many years and is increasingly becoming a priority in European fisheries as well. While technical, regulatory and social approaches have all been recognized as ways to reduce bycatch, they are not always effective (Little et al., 2014).

 

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Bycatch from the Gulf of Mexico shrimp trawl fishery. Photo credit: Elliott Norse, Marine Conservation Institute/Marine Photobank

 

Currently, the primary methods of reducing bycatch involve either creating fishing closures or improving the selectivity of fishing gear. The primary problems with fishing closures are that they can be difficult to enforce and are unresponsive to changes in fish stocks (Little et al., 2014). Increasing the selectivity of fishing gear can create problems when the technology decreases catch of the target species (see figure 2 for an example of a successful gear modification). If the profitability of the fishery is negatively impacted fishers are less inclined to use selective fishing gear (Little et al., 2014). Alternatively, real-time spatial management plans are responsive to changes in stock dynamics and have been proposed as a way for fisheries to reduce their bycatch without impacting the catch of their target species (Little et al., 2014).

 

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Figure 2. A loggerhead sea turtle escapes from a trawl through a turtle exclusion device. Photo credit: http://www.sefsc.noaa.gov/labs/mississippi/images/loggerhead_ted-noaa.jpg

 

Real-time spatial management plans have been introduced in select European and American fisheries to help encourage vessels to leave areas of high bycatch. Since these plans are relatively new, Little et al., (2014) reviewed ten fisheries across the US and Europe to summarize how real-time spatial management has been successful and where improvements can be made.

While each real-time spatial management plan was tailored for it’s respective fishery, all of the fisheries used their own catch and discard observations to identify areas of high bycatch. Once bycatch levels were identified fishery closures were updated and the news was communicated to the fleet. The time it took fishery closures to be updated varied from hours to weeks depending on the fishery. Real-time spatial management plans benefit fisheries because once areas of high bycatch are identified fishers can avoid them, thus saving time and money. Additionally, there is a positive feedback loop that gives fishers a sense of empowerment and responsibility in managing the natural resources they depend on for their livelihoods (Little et al., 2014).

While real-time spatial management sounds promising, its success depends on the existence of strong leadership and infrastructure (Little et al., 2014). Strong governmental or local leadership is necessary to create and manage fisheries management plans. A strong infrastructure is required to create a real-time communication system that facilitates the collection and monitoring of findings. Additionally, participation, enforcement, and the physical and ecological characteristics of the fishery also influence the success of the plan (Little et al., 2014).

Under the right circumstances real-time spatial management has the potential to greatly assist in mitigating bycatch. However, until the plans are fully developed they should be used in conjunction with other bycatch mitigation measures. Future research is required to determine if using real-time spatial management plans can help mitigate fisheries bycatch over the long term.

 

Reference:

Little, A.S., Needle, C.L., Hilborn, R., Holland, D.S., & Marshall, C.T. (2014). Real-time spatial management approaches to reduce bycatch and discards: experiences from Europe and the United States. Fish and Fisheries. First published online: 18 March 2014. DOI: 10.1111/faf.12080

 

 

 

Whale Conservation in the Mediterranean

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By Jessica Wingar, RJD Intern

Conservation of threatened species is very critical in order to maintain the state of our oceans. There is a wide range of reasons for why the species needs to be conserved from threat of boat strikes to disease outbreak. However, humans cause many of these threats. In an effort to protect these threatened species from humans, marine protected areas, or MPAs, can be established. In this study, researchers were looking at whether it would be more effective to establish a series of MPAs or to restrict shipping through the International Maritime Organization, IMO, in order to protect the Mediterranean fin whale. The researchers looked at the advantages and disadvantages to all of the options available to determine what would be the best method of protection for a wide-ranging cetacean such as this species of fin whale.

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Current distribution of the Mediterranean fin whale in the Mediterranean Sea.

Researchers from University College London and Stockholm University looked at the current state of the Mediterranean fin whale and the causes of its need for conservation to devise the most effective course of action to protect this species. This species of fin whale is on the IUCN’s red list as Vulnerable. The main threat facing this species is collisions with ships. One of the issues facing the protect of Mediterranean fin whales is that a lot of the Sea is not governed by any particular country. However, some of the countries bordering the Mediterranean are currently trying to create a collection of MPAs to protect these waters.

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Current protected areas in the Mediterranean

In the study, the researchers concluded that including IMO in the conservation of whales would lead to increased protection of these animals. One of these reasons is that this organization has the tools to monitor the area in order to decrease factors that lead to whale and boat collisions. One of these ways would be to order a reduction in boat speed. If IMO puts this law into place, it becomes mandatory for all of the member nations of IMO to follow this. IMO is also respected in the shipping industry, so by them recognizing the threat of ships to whales, other vessels will follow creating a cascading effect. In addition, changes can occur quickly under IMO  and ships are more likely to feel inclined to follow the rules of IMO than if the area was a MPA.

Studies of this nature are very important because they discuss an alternative plan for protection and start a discussion about the pros and cons of each plan. IMO and the governments of the countries involved will, hopefully implement the plan for conservation that the researchers devised. Thus causing greater plans for the protection of the Mediterranean fin whale.

 

Reference

Geijer, C. K.A., and Peter J.S. Jones. “A network approach to migratory whale conservation: Are MPAs the way forward or do all roads lead to the IMO?” Marine Policy 51 (2014): 1-12.

Fuel consumption of global fishing fleets

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By Gabi Goodrich, RJD Intern

Everyone is well aware of the problem of overfishing. Fishing fleets go out and fish until they meet their quota. While over fishing is a major problem for the oceans health, another, less talked about side of the issue is the fuel consumption of those fishing fleets. As the “fight to fish” grows, fleets have become bigger and more powerful fleets. With the public concern for green products, the use of high emission energy sources has been put into the spotlight. In an article titled “Fuel Consumption of Global Fishing Fleets: Current Understanding and Knowledge Gaps,” Robert W R Parker and Peter H Tyedmers studied more than 1,600 records of fuel use by fleets worldwide using all types of fishing methods.

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A shrimp trawler hauling in nets. Photo Credit – Robert Brigham, NOAA Photo Library

 

It is apparent that some are bigger offenders than others. Some of the most popular foods hold the top ten spots, with shrimp and lobster coming in at number one for worst offenders. It is interesting to see that the global difference between fishing practices. While globally, shrimp and lobster hold an average of 2932 liters per ton, the fuel use intensity (FUI) is 783 liters of fuel to catch one ton of Maine Lobsters from traps, while the Norway Lobster takes 17,000 liters of fuel per ton in the North Sea (Parker 2014). These variations, however, can be attributed to different fishing styles, gear, and availability and magnitude of what they are trying to catch. Those to have to travel farther and longer distances to find the desired catch use more fuel than those who have to travel shorter distances and have greater potential to land the desired catch. Catches like the Peruvian Anchovy, Atlantic Mackerel, and Australian Sardine are some of the most efficient fisheries and are some of the largest fisheries globally, by volume of landings. The use of purse seine gear or other surrounding nets average an FUI of 71 liters per ton while trawling for small pelagic fish has an FUI of 169 liters per ton (Parker 2014).

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A boat and lobster pots. Photo credit – Bob Jones

 

So what does this all mean? According to the FUI records, the median value is 239 liters per ton. That’s roughly an average of two kilograms of carbon dioxide produced per kilogram of seafood caught and landed. To put that into perspective, beef has an average of just over 10 kilograms of CO2 per kilogram produced, pork has just less than 6 kilograms of CO2 per kilogram. While compared to other sources of food, the production and fishing of seafood is relatively low. The study does have some serious implications. The most efficient sources of fishing (small pelagic fisheries) are often overlooked as a viable food source in developing countries and are instead used for aquaculture and livestock. Furthermore, with fuel prices on the rise and carbon emission regulations and laws growing stricter, the profitability of the fishing industry will be compromised. Parker and Thyedmers say the most effective way to improve the energy performance of fisheries is to rebuild stocks and manage capacity effectively.

 

Patterns of serial exploitation of sea cucumbers in the Great Barrier Reef Marine Park

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By Jake Jerome, RJD Graduate Student and Intern

There is no doubt that overfishing is a major threat to ocean ecosystems. When most people think of overfishing, they think of the over harvesting of fish species that many in the world rely on. However, there are species besides fish that face the threat of exploitation. Eriksson and Byrne found in 2013 that the tropical sea cucumber fishery in Australia’s Great Barrier Reef Marine Park (GBRMP) is following patterns of overexploitation.

To reach this conclusion, the authors performed a meta-analysis of catches in the fishery from 1991 to 2011 by reviewing data published in peer reviewed literature and fisheries reports.  From their analysis they found that the sea cucumber fishery initially focused only on harvesting high-valued species but shifted towards lower-valued species over time. The initial target was black teatfish (Holothuria whitmaei) until 1999, when a 70% decline in the catch of black teatfish was noted, and subsequent effort then shifted towards the white teatfish (H. fuscogilva). The fishery was subsequently diversified after the collapse of the black teatfish to include other species of medium and low-value. Despite the addition of these new species into fishery efforts in 1999, most of them no longer appeared on catch lists as of 2005. Two new key target species prompted an increase in the harvest during the 2004 to 2011 period, though they were species of lower value than the teatfish.

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Catch records from the Queensland East Coast bêche-de-mer fishery (ECBDMF). The three areas indicated in the figure are conceptual periods in the fishery based on the composition of catch. (Eriksson and Byrne 2013)

A major problem with the sea cucumber fishery in the GBRMP is the lack of information about the original population sizes of the species targeted. Without a baseline of knowledge, predicting the critical threshold beyond which a species can no longer recovery is extremely difficult. Because of this, many of these species may have been fished past their critical threshold and may not be able to avoid extinction.

With Australia being a developed high-income country, it is expected that management of fisheries is better resourced then it would be in low developed countries. This study showed that serial expansion and the quick replacement of high-valued species with lesser valued individuals is not limited to fishing practices in low-income developing countries and is a common trend in the overexploited global sea cucumber fishery. This is important to the fishery because it points out gaps in the management of sea cucumbers. Although Australia tried to manage this particular fishery with a rotational zoning scheme (RZS) in 2004, it proved to be either too late or ineffective. In addition, this study illustrates that providing relatively few fishermen access to a large fishing area through licensing, does not necessarily transfer to sustainable sea cucumber harvest.

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White teat sea cucumber (Holothuria fuscogilva). (Stacy Jupiter/Marine Photobank)

In the end, it is clear that more studies need to be done on population sizes of tropical sea cucumbers to accurately assess their vulnerability. Without being able to monitor populations as they are harvested, effectively managing the many now threatened or endangered sea cucumbers will continue to be a problem.

Reference

Eriksson, H. and Byrne, M. (2013), The sea cucumber fishery in Australia’s Great Barrier Reef Marine       Park follows global patterns of serial exploitation. Fish and Fisheries. doi: 10.1111/faf.12059