Extreme Breath Holding: Marine Mammal Diving

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by Emily Nelson, RJD Intern

Sperm whales have been recorded diving to depths well over 2,000 meters. Elephant seals have recorded dives lasting over 2 hours. Humans, on average, can hold their breath underwater for less than 30 seconds. How is it that marine mammals spend such long periods of time underwater, diving to incredible depths? After all, they breathe oxygen just as terrestrial mammals do. The answer lies in the many adaptations these animals have acquired over time that completely change how oxygen is stored, delivered, and used in the body.

The incredible diving capabilities of marine mammals are shown in this table.

The incredible diving capabilities of marine mammals are shown in this table.

Contrary to what you may think, the lungs are not a primary site of oxygen storage in marine mammals. The purpose of the lung is to exchange gases between blood and the air. This function is largely restricted while diving; with increasing pressure, resulting from increasing depth, the lungs and trachea decrease in size and eventually collapse. However, this collapse helps to prevent nitrogen narcosis. Commonly known s the bends, this is a problem and concern for SCUBA divers. At depth nitrogen moves into the bloodstream rapidly and can cause gas bubbles to form in the body, blocking the flow of oxygen. In marine mammals, as lung size decreases air is forced into the upper airway spaces. These areas do not exchange gases with the blood and thus nitrogen is prevented from entering the blood stream altogether, allowing them to avoid the bends.

Despite decreased lung capacity, increased total body oxygen is a necessary component in the ability of marine mammals to hold their breath. /’|/Oxygen consumed during a dive is stored in three areas: muscles, blood, and lungs. Marine mammals have large stores of oxygen in their muscles and blood, acting almost like an on board scuba tank. Myoglobin (oxygen binding protein in muscle) is present at levels three to seven times higher than in terrestrial mammals. This internal store of oxygen is used for much of the animal’s aerobic metabolic needs. In addition, the amount of blood in a marine mammal is proportional to the depth at which it dives. Increased blood volume and hemoglobin (oxygen binding protein in blood) lead to higher oxygen stores. The concentration of red blood cells is also increased. Red blood cells carry oxygen, and as an animal starts a dive it sends red blood cells through the blood stream until it returns to the surface. The extent to which an animal shows these adaptations varies between species, but the amount of oxygen available and its utilization has a big impact on how long an animal can hold its breath for all marine mammals.

In addition to marine mammals’ increased ability to store oxygen, they can also decrease their oxygen consumption during a dive using bradycardia and selective ischemia. Bradycardia is a rapid decrease in heart rate upon starting a dive. An orca whale has the ability to go from a heart rate of 60 beats per minute to 30 beats per minute in a matter of 15 seconds. Heart rate during a dive is nearly the same as heart rate experienced during a respiratory pause. This decreased heart rate is then maintained for the duration of an animal’s dive. Because the heart is beating slower it is performing less work and oxygen consumption is reduced. The extent to which bradycardia occurs is proportional to the length of the dive, the longer a dive the slower the heart rate. As a dive nears completion an animals’ heart rate increases drastically in process known as anticipatory tachycardia.

Selective ischemia is the redistribution of blood to the most vital organs, the brain and heart. This deprives the kidneys and liver of blood and they may shut down during the dive. By limiting blood circulation oxygen is conserved and metabolic rate is decreased. Blood flow to muscles is minimal, but they still need to function in order to swim. Muscles can rely on internal myoglobin stores as well as anaerobic (without oxygen) metabolism. Muscles can withstand anaerobic metabolism due to their high tolerance for lactate. Upon surfacing blood flow returns to normal and these areas are flushed with blood, coming back to normal function almost immediately.

A humpback whale descending.

A humpback whale descending.

These are among the major adaptations marine mammals have gathered over time, allowing them to dive longer and to greater depths than any terrestrial mammal. They have the ability to readily adapt from surface conditions to conditions at extreme depths. However, there is still a lot to be learned about how these animals can survive under such unique circumstances.

REFERENCES

Hoelzel, A. Rus. Marine Mammal Biology: An Evolutionary Approach. Oxford: Blackwell Science, 2002. Print.

Kooyman, Gerald L. “Marine Mammal Diving.” Encyclopedia of Marine Mammals. 2nd ed. Oxford: Academic, n.d. 327-32. Print.

Richardson, Jill. “Anatomy and Physiology II.” MSC 350. University of Miami, Coral Gables. Mar. 2013. Lecture.

Communicating Science Through Film

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by Fiona Graham, RJD Graduate Student and Intern

Utilizing film as a media to communicate science can be a powerful way to quickly reach large numbers of the general public in a user friendly way. Whether it’s newly published scientific research, or you’re trying to promote scientific awareness for conservation purposes, choosing to create a short online based film about the topic is a great way to get involved in outreach and education. Promoting science through outreach is extremely important to conservation efforts, as, often, awareness about an issue can be a major barrier in conservation efforts. I see this first hand when conversations with new acquaintances inevitably turn to the “what do you do” small talk, and as a result of my research on sharks for my masters, I frequently find myself talking about shark population declines. It’s not surprising to me anymore that most people have no idea how threatened some shark species are, have never heard of shark fin soup, and don’t know what bycatch is.

Reaching the general public about these issues and new research results can be difficult, especially because non-scientists don’t often read published papers or necessarily speak the language. However, with the online resources we have available now it can be quite easy to quickly reach large numbers of people around the world. Social media platforms like Facebook, Twitter, and Instagram make sharing content simple. Short, online based films are a particularly great way to get across a message because it can be very engaging to the average person. In addition, a good educational film can easily be used again and again as a tool in classrooms around the world. Viewing platforms like YouTube and Vimeo can also give useful insight into view counts and the film’s audience demographic, helping to quantify outreach efforts.

Data from YouTube helps to quantify outreach efforts.

Data from YouTube helps to quantify outreach efforts.

One of the reasons I love being a part of the RJ Dunlap Marine Conservation Program is that the value of outreach and communicating research is recognized and embraced. RJD has a full time media specialist and media focused interns that work with our scientists to communicate their research to the world through online virtual learning experiences, photographs and, of course, film.

Welcome to RJD, an introduction video. Watch it here: https://vimeo.com/21759088

Welcome to RJD, an introduction video. Watch it here: https://vimeo.com/21759088

In addition to the benefit that a film’s audience can derive from the experience, the process of filming, editing and publishing your own film about your research as a scientist can be a great creative outlet and quite rewarding. There is no room for creativity in science, or showing your personality through publications, however film is another story.

Waterlust, an organization I help run along with a couple other graduate students, is focused on creating these online based films in order to inspire more people to care about our environment. We mix the science and conservation in with sports such as freediving, kiteboarding, and sailing in order to pull more people in that wouldn’t otherwise seek out the science themselves. Taking this route we believe we’re able to reach more people that don’t already care, and hopefully get them to consider their own connection with the ocean, what water means to them, and educate them about issues facing our marine environment in order to inspire respect for these resources. This particular strategy is called entertainment-education (Singhal & Rogers, 1999). At Waterlust we often advocate for scientists becoming their own filmmakers, however collaborations between scientists and filmmakers can also result in successful ways in which to connect research with the public. The point is to get the information out there through an engaging, effective medium: film.

It’s important to note that I’m not at all suggesting that film will ever replace peer reviewed articles in scientific journals, only that it is a great supplement to said publications. In fact, a major barrier to film becoming a more mainstream way in which to communicate science is that it is not peer reviewed. With regards to this, it is important to maintain integrity and stick to true, science based information. That said, film is definitely gaining traction within the scientific world. Support for film is seen through contests such as Ocean180, sponsored by the Florida Center for Ocean Sciences Education Excellence (COSEE Florida), and NSF’s video contest. Video abstracts accompanying papers are becoming more popular, and many scientists are recognizing its value for broader impacts.

REFERENCES

Showstack, R. (2013), Ocean Science Video Challenge Aims to Improve Science Communication, Eos Trans. AGU, 94(40), 351.

Singhal A, Rogers E.M. (1999), Entertainment–education: a communication strategy for social change. Lawrence Erlbaum Associates, Mahwah, NJ

Impact of Costa Rican Longline Fishery on its Bycatch Species

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by Fiona Graham, RJD Graduate Student and Intern

Bycatch, the incidental catch of non-target species, tends to be high when using non-discriminatory fishing methods, such as longlining. Longline fisheries, such as that of Costa Rica, generally target mahi mahi and silky sharks, however data collected by an observer program shows that a large percentage of their catch is olive ridley turtles and non-target shark species. These longlines literally consist of long lines of baited hooks that stretch for miles and soak in the water for hours. Unfortunately, fisheries bycatch is one of the primary reasons for population declines in sharks, rays and sea turtles.  This is due to their life history characteristics, such as long lifespans, late age of maturity, and few offspring, that make them inherently sensitive to these high rates of mortality.

In a recent paper describing the impact of the Costa Rican longline fishery on its bycatch species, authors Derek Dapp et al. examine the catch numbers, capture locations, seasonality and body size of non-target sharks, sting rays, bony fish and olive ridley turtles. The paper uses data from the fishery observer program from 1999 to 2010 where observations were conducted onboard six medium scale vessels out of a Costa Rican fleet of 350 vessels. One troubling, but not so surprising result of their analysis found that the olive ridley turtle was the second most abundant species captured by the fishery. Two of the six major beach nesting aggregations for olive ridleys in the world are in Costa Rica, and populations at these two main nesting beaches have declined since the 1980s. Based on (most likely an underestimate) of the number of olive ridleys caught by the fishery – 290,500 a year – the impact of the Costa Rican longline fishery on olive ridleys needs to be greatly reduced.

Olive ridley sea turtle (photo: Wikimedia Commons).

Olive ridley sea turtle (photo: Wikimedia Commons).

Large numbers of sharks and rays are also caught as bycatch by the longline fishery, where rays are thrown back overboard and sharks are retained for their fins, meat, or as bait. Notably, the authors were able to identify a blacktip nursery near the Osa Peninsula due to the presence of high catch rates of juvenile blacktip sharks during the spring and summer months.

Catch per 1000 hooks on longlines for blacktip sharks, indicating the presence of a nursery ground near the Osa Peninsula (figure: Dapp et al. 2013).

Catch per 1000 hooks on longlines for blacktip sharks, indicating the presence of a nursery ground near the Osa Peninsula (figure: Dapp et al. 2013).

As well as affecting blacktip sharks, the authors found that the fishery affected the other two species of shark that they examined, silky sharks and pelagic thresher sharks. They concluded that there is a clear need for more effective management of the Costa Rican fishery.

While this is an obvious conclusion to be made here based on the data available, the specific management protocol and how that management is put into place and enforced is a more complicated discussion. In this recent paper, Dapp et al. criticize many fisheries biologists for believing that the only acceptable methods of reducing bycatch are those that do not inconvenience fisherman or reduce their target catch substantially. They conclude that the only solution is through reduction of fishing effort through creation of marine protected areas or time area closures. They also suggest placing observers on at least 50% of medium and larger fishing vessels to acquire more data on fishing methods and bycatch and to educate fishermen to improve their techniques and to release bycatch species alive.

Current and Future Conservation Efforts for the Critically Endangered Smalltooth Sawfish (Pristis pectinata)

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by Laurel Zaima, RJD Intern

The endangerment and extinction of many plant and animal species is often due to a direct anthropogenic impact on the environment. If humans cause the endangerment of a species, humans should be held responsible for recovery of that species. Unfortunately, this is the case for the incredibly unique elasmobranch, the smalltooth sawfish (Pristis pectinata). The smalltooth sawfish populations began globally declining during the mid to late 20th century due to a variety of irresponsible anthropogenic practices (“Pristis pectinata”). International and national conservation actions have been taken in the past ten years to help prevent the sawfish from becoming extinct; however, the smalltooth sawfish is still considered critically endangered. The smalltooth sawfish has the potential to be removed from the International Union for Conservation of Nature (IUCN) endangered red list if more research is gathered to better develop conservation programs, and if the current conservation laws are enforced and enacted by the public.

The morphology of the smalltooth sawfish has an indirect influence on the depletion of the sawfish population. Smalltooth sawfish average a weight of 350 kilograms, a length of 5.5 – 7 meters, and an age of 25-30 years (“Smalltooth Sawfish”).  Similar to many sharks, the smalltooth sawfish have a low reproductive rate because they grow slow, mature at a late age, and produce few young per liter (“Sawfish Facts”). These characteristics make it difficult for the smalltooth sawfish populations to recover in a timely manner, especially when they are subject to anthropogenic threats (“Sawfish Facts”). The smalltooth sawfish, as suggested, is known for their “saws,” also known as a rostrum, which are long, flat snouts edged with pairs of teeth that they use to locate, stun, and kill their prey (“Sawfish-Cousins of the Shark”).

The rostrum of a smalltooth sawfish is edged with pairs of teeth that they use for predation.

The rostrum of a smalltooth sawfish is edged with pairs of teeth that they use for predation.

The smalltooth sawfish’s large size and the protruding rostrum make them especially vulnerable to bycatch by various fishing gear. Net fishing gear, especially gillnets and trawl nets, have high tendency to tangle around the rostrum of the sawfish (“Sawfish Facts”).  Occasionally, fishermen will kill the sawfish before they were removed from the fishing gear in order to prevent damage to the fishing gear or danger to the fisherman (“Smalltooth Sawfish”). During the 1970s, recreational and commercial fishers would catch smalltooth sawfish mainly for their meat (“Sawfish-Cousins of the Shark”).

Historically, fishermen easily caught smalltooth sawfish for meat using a variety of fishing gear, including gill nets and trawl nets.

Historically, fishermen easily caught smalltooth sawfish for meat using a variety of fishing gear, including gill nets and trawl nets.

Today, sawfish are intentionally caught less for their meat, but more for the value of their saws, fins, and teeth in the illegal wildlife trade (“Sawfish-Cousins of the Shark”).

Anthropogenic habitat degradation has also contributed to the exponential decline of the smalltooth sawfish population, and it has tremendously limited their habitat distribution. Smalltooth sawfish inhabit shallow coastal waters with muddy, sandy bottoms of the tropical sea, estuaries, and mangroves (“Smalltooth Sawfish”). Extensive habitat modifications and losses of the smalltooth sawfish is directly caused by agricultural and urban development, commercial activities, dredge-and-fill operations, boating erosion, and diversion of freshwater runoff from coastal and catchment development (“Pristis pectinata”). A study by Simpfendorfer, Wiley, and Yeiser (2010) used active tracking and passive acoustic monitoring of the juvenile smalltooth sawfish in order to understand the fine scale movements and habitat in southwest Florida. Shallow banks close to estuaries and mangrove shorelines were found to be especially important nursery areas for juvenile smalltooth sawfish (Simpfendorfer, Wiley, Yeiser, 2010). Unfortunately, much of these areas have been damaged or lost due to human development.  The loss of nursery areas declines the smalltooth sawfish reproductive ability and prevents this species from restoring their population. The acoustic telemetry data collected by C. A. Simpfendorfer of the Mote Marine Laboratory (2001) indicates that smalltooth sawfish in the Everglades National park had high levels of site fidelity and preferred to inhabit an area for months. Since sawfish do not regularly migrate, the destruction of shallow coastal waters, estuaries, and mangroves can increase the levels of mortality of the sawfish in that area.

The smalltooth sawfish once flourished international waters, but habitat loss has nearly extirpated their distribution range. Historically, the smalltooth sawfish populated U.S. waters ranging from the Gulf of Mexico (Texas to Florida), and along the east coast from Florida to Cape Hatteras; internationally, the smalltooth sawfish populated South Africa, Madagascar, the Red Sea, Arabia, India, the Philippines, along the coast of West Africa, portions of South America, Ecuador, the Caribbean Sea, the Mexican Gulf of Mexico, and Bermuda (“Smalltooth Sawfish”). The global and U.S. distribution of sawfish is estimated to have profoundly declined. The smalltooth sawfish is currently found in the southeastern U.S., specifically Florida, the Bahamas, Cuba, Honduras, and Belize (“Pristis pectinata”). The distribution of smalltooth sawfish in other parts of the world is uncertain because there is a lack of population surveys and biological research towards this species (“Pristis pectinata”). While the presence of sawfish is ambiguous, major anthropogenic threats and few local population surveys serve as evidence to suggest that the distribution range and population of sawfish has drastically decreased.

Currently, international and national conservatory action has been enacted in hopes to restore the smalltooth sawfish population. The United States has initiated a variety of programs that spread awareness of the smalltooth sawfish endangerment, educate to the public regarding their population status, and conserve and protect the smalltooth sawfish. The Smalltooth Sawfish Recovery Team is comprised of scientists, managers, and environmental managers that plan to recover the U.S. population of the smalltooth sawfish (“Smalltooth Sawfish”). The Smalltooth Sawfish Recovery team collaborated with the National Marine Fisheries Service (NMFS) to formulate the final recovery plan in January 2009, which strives to reduce fishing impacts, protect important habitats, educate the public, and provide guidelines to fishermen on safely handling and releasing sawfish (“Smalltooth Sawfish”). In 2003, the Endangered Species Act (ESA) listed the smalltooth sawfish as the first elasmobranch classified as endangered (“Sawfish Facts”). The protection under the ESA means that it is illegal to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or attempt to engage in any form of contact with a smalltooth sawfish (“Pristis pectinata”). The ESA has been able to provide a framework for the conservation and recovery of the smalltooth sawfish by better protecting the species and their habitats throughout the U.S. In 2009, the National Marine Fisheries Service established a critical habitat for juvenile smalltooth sawfish in the U.S., which is designed to facilitate recruitment into the adult sawfish population by protecting juvenile nursery areas (“Pristis pectinata”). Within the U.S., Florida, Louisiana, and Texas have prohibited the “take” of sawfish, and Florida banned the use of gill nets in state waters and established three national wildlife refuges to protect the smalltooth sawfish habitat (“Smalltooth Sawfish”). The quick and extensive conservative action taken by the U.S. has allowed the smalltooth sawfish population to stabilized in national waters.

Internationally, conservative action towards the smalltooth sawfish has also been implemented. All species of sawfish are listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which bans the commercial international trade of sawfish or sawfish parts (“Pristis pectinata”). Individual countries have taken personal conservatory action towards the protection of the smalltooth sawfish. Nicaragua imposed a permanent ban on targeted sawfish fishing in Lake Nicaragua; Brazil has protected the smalltooth sawfish by the Ministry of Environment; Mexico has banned the take of all sawfish; sawfish are protected under the Exclusive Economic Zone in Guinea and Senegal, and in the marine protected areas in Mauritania and Guinea-Bissau (“Pristis pectinata”). Although there are many programs, strategies, and laws that strive to protect the smalltooth sawfish, this species is still considered critically endangered. Therefore, further action must be taken in hopes to recover the smalltooth sawfish population and to stabilize their species.

In order for the smalltooth sawfish species to bounce back from critical endangerment, more research and population surveys needs to be globally conducted, and the conservation programs that are already initiated must be enforced. Further information regarding the distribution and abundance of the smalltooth sawfish needs to be collected more frequently, and across a larger area to obtain an accurate estimation of the species population. A smalltooth sawfish study conducted by C. A. Simpfendorfer of the Mote Marine Laboratory (2001) successfully surveyed south Florida to determine the distribution and abundance, utilized acoustic and satellite telemetry to investigate movements and habitat utilization, used the public reporting database to gather data on sawfish encounters by the public, and studied the population dynamics and conservation genetics to investigate how the population decline has impacted the genetic diversity.

Research Scientists install a tag on a sawfish to monitor its movement and home range.

Research Scientists install a tag on a sawfish to monitor its movement and home range.

This research provides useful information about the smalltooth sawfish, but unfortunately, it is limited to the southern Florida area. More research, similar to this study, must be conducted worldwide to fully understand the sawfish population and to create effective conservation programs for this species. According to a study performed by Carlson et al. (2012), there is little scientific research about the sawfish critical habitats and the environmental conditions of these habitats; however, there are large amounts of nontraditional data that comes from public encounters voluntarily reported to members of the recovery team. The nontraditional data is helpful in obtaining an idea of the smalltooth sawfish habitats, but this data is not as reliable as scientific research. Unfortunately, the immediate need to protect the smalltooth sawfish habitat by the ESA and a lack of research resulted in the use of the nontraditional data to designate critical habitats (Carlson et al., 2012).  There is an imperative need for more scientific research about the smalltooth sawfish habitat and their movement patterns in order to accurately initiate protective strategies.  Some additional policy and conservative recommendations include: training local fisheries to conduct sawfish surveys in key regions including West Africa, Borneo, Brazil, India, and Papua New Guinea; helping key regions develop national and regional plans to recover sawfish; creating sawfish identification manuals to aid fishermen, customs agents, and enforcement personnel in preventing illegal trade; reducing sawfish bycatch in trawl and gillnet fisheries around the world (“Sawfish-Cousins of the Shark”).

Although significant progress has been made towards the conservation of the smalltooth sawfish, there is still a lot of research and conservatory action that needs to occur. If expedite action is taken, the smalltooth sawfish can avoid extinction and be removed from the IUCN critically endangered list.

REFERENCES

Carlson, J. K. et al. 2012. “Designating Critical Habitat for Juvenile Endangered Smalltooth Sawfish in the United States.” Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science 4: 473-480.

“Pristis pectinata.” The IUCN Red List of Threatened Species. n.p., 2013. Web. 7 Oct. 2013.

“Sawfish-Cousins of the Shark.” NOAA Fisheries. n.p., 15 Aug. 2012. Web. 7 Oct. 2013.

“Sawfish Facts.” MOTE Marine Laboratory. n.p., 2012. Web. 7 Oct. 2013

Simpfendorfer, Colin A. (2001). Occurrence and Movements of Sawfish in Southern Florida. National Geographic Society’s Committee for Research and Exploration: Sarasota, Florida. 787.

Simpfendorfer, Colin A., Wiley, Tonya R., Yeiser, Beau G. 2010. “Improving Conservation Planning for an endangered Sawfish using data from Acoustic Telemetry.” Biological Conservation 143: 1460-1469.

“Smalltooth Sawfish.” NOAA Fisheries Office of Protected Resources. n.p., 26 Aug. 2013. Web. 7 Oct. 2013.

Global Fishmeal and Fish-oil Supply

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by Beau Marsh, RJD Intern

Fishmeal and fish-oil are global commodities produced for both animal and human consumption.  These products are manufactured from whole fish catches, as well as the by-products of fish processed for human consumption.  Fishmeal and fish-oil are utilized for livestock and aquaculture feeds, and fish-oil is being increasingly sought after by people for the omega-3 fatty acid content.  In the review paper by Shepherd & Jackson (2013), information from the United Nations Food and Agriculture Organization (FAO) and the International Fishmeal and Fish-oil Organization (IFFO) is used to analyze the trends of fishmeal and fish-oil use.  The data also suggests the role fishmeal and fish-oil will play in the future of animal and human consumption.  In the past 50 years, fishmeal and fish-oil consumption has seen considerable change.

World fishmeal ( ) and fish-oil ( ) production for 1964–2011 ( , El Ni˜no years)(source: Shepherd & Jackson 2013).

World fishmeal ( ) and fish-oil ( ) production for 1964–2011 ( , El Ni˜no years)(source: Shepherd & Jackson 2013).

 

Global production increased from the 1960’s until it peaked in 1995.  Since 1995, there is a clear pattern of decreasing annual production.

Fishmeal and fish-oil predominantly come from forage fishes (i.e. whole fishes), while an additional portion come from the processed by-products of fishes caught for human consumption.

Fishmeal and fish-oil industry supply-chain (source: Shepherd & Jackson 2013).

Fishmeal and fish-oil industry supply-chain (source: Shepherd & Jackson 2013).

Fishmeal offers a nearly optimal diet for animal feeds.  Its benefits were initially recognized for agricultural purposes.  In 1960, agriculture constituted 98% of fishmeal consumption, splitting it between pig and poultry feeds.  Aquaculture has grown to the dominant use of fishmeal and fish-oil.  Presently, aquaculture has expanded to the point where it consumes over 73% of global fishmeal production.

Source: Shepherd & Jackson 2013.

Source: Shepherd & Jackson 2013.

In regards to fish-oil, its main purpose was for both margarines and shortenings or for various industrial uses.  After fish farming began in the 1980’s, it has expanded to where aquaculture now consumes over 80% of global fish-oil production.  In addition, fish-oils high in omega-3 fatty acids, notably eicosapentaenoic  acid (EPA) and docosahexaenoic acid (DHA), are increasing in demand for human consumption.

Source: Shepherd & Jackson 2013.

Source: Shepherd & Jackson 2013.

With the growth of these emerging markets, there is a greater demand on the fishmeal and fish-oil industry.  Due to recent, more stringent fisheries regulation, there is a reduced source of whole fishes available.  Therefore, greater amounts of fish by-products are being incorporated into the final products, and marine ingredients in fishmeal compounds are becoming more expensive.  A cost effective response has been to substitute in vegetable components and land-animal by-products as a cheaper source of proteins and lipids.  This is not an ideal solution because of potential human health concerns such as transmissible spongiform encephalopathies (TSE).  It also causes a diminishing effect on the fatty acid make-up of the fish.

Multiple approaches are being taken to solve the fact that the need for fishmeal and fish-oil continues to grow, but their production remains static or decreases.  Possible future solutions may be genetically modified plants or transgenic farmed fish, both of which would render high levels of omega-3 fatty acids.  However, genetic modification inevitably receives consumer criticism, so these techniques are unlikely in the near future.  Another solution already underway is the use of other sources such as krill species and algal biomasses for the valuable oils.  This should hopefully reduce some pressure on the omega-3 oil resources; however, the incorporation of vegetable oils continues to increase.

A separate issue affecting fishmeal and fish-oil resources is the lack of regulation and responsible management in Asian fisheries.  These fisheries are among the world’s largest aquaculture producers, but decades of overexploitation have hurt production.  Additionally, the regional practice of feeding with trash fish exacerbates the problem.  Low-level trash fish causes the depletion of fisheries and diseases to spread throughout the fishes.  These instances of poor management have triggered multinational agencies to work with local governments in order to implement healthier practices.

Every year fewer marine ingredients are available because of increased fisheries regulation and the increasing demand from aquaculture and human consumption markets.  While it is fortunate to see responsible management implemented over fisheries, emergent challenges arise.  These challenges have sparked innovation which has developed alternatives (some more controversial than others) to the forage fish supply.  Substituting marine ingredients has proven to be efficient in aquaculture, but what are the implications for the end consumer?  While the fish species may show successful growth, there are reduced levels of omega-3 fatty acids in the fishes.  These oils can also be extracted from algae or krill, but it is less efficient.  Fishmeal and fish-oils are valuable resources that require responsible and efficient management which without could mean compromising the health of human consumers and aquacultures.

REFERENCE

Shepherd, C. J. and Jackson, A. J. (2013), Global fishmeal and fish-oil supply: inputs, outputs and marketsa. Journal of Fish Biology, 83: 1046–1066. doi: 10.1111/jfb.12224

Sea Level Rise: How bad is it really going to be?

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by Gabi Goodrich, RJD Intern

For years scientists have been discussing the effects of global warming, carbon emissions and those effects on the oceans. But how bad is it really? Currently the rate of sea-level rise is about 3.2 millimeters per year (about .13 inches per year) [1].  However, with our current output of carbon emissions, scientists say that rate will increase tenfold. This means we have “locked in” a fate of sea levels rising 1.3 – 1.9 meters (4.27 – 6.23 feet) higher than today. Anders Levermann and his team of scientists have found that the sea levels are hyper sensitive to global warming. In fact, for every degree Celsius increase in global temperature, sea levels will rise about 2.3 meters (7.55 feet).

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Marine protected area help recover fish without harming fishers

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by Kyra Hartog, RJD Intern

With fisheries collapsing around the world, Marine Protected Areas (MPAs) have emerged as a potential solution to allow fish stocks to recover to a level at which they may be harvested sustainably. There are several types of MPAs, ranging from areas with some fishing allowed to no-take reserves. Though MPAs are widely considered as fishery recovery tools, there has been little empirical evidence showing the benefit a fishery may receive from an MPA. In addition, fishermen generally believe that an MPA will come with an economic cost, possibly related to decreased catch rates and increased boat travel time. In their recent paper, Kerwath et. al (2010) demonstrate the effectiveness of the no-take Goukamma MPA off the coast of South Africa with no apparent cost to fishermen.

The focus species of this study was the roman (Chrysoblephus laticeps), a seabream endemic to the South coast of South Africa that inhabits rocky reefs. The species is targeted as part of a larger fishery directed toward rocky-reef dwelling predatory fish. Due to lifestyle characteristics such as long lifespan and broadcast spawning reproduction, the roman is vulnerable to overexploitation and has been heavily depleted along the South African coast. Fishermen have been required to report species and boat catch data since 1985, providing five years of roman catch data before the Goukamma MPA was implemented in 1990. The study then examined catch data for ten years following the MPA’s implementation. The specific metrics used in this study were catch per unit effort (CPUE), which was used as an indicator for roman abundance, and total roman catch.

The researchers found that in the years leading up to and during the first year of the Goukamma MPA implementation (1985-1991), total roman catch decreased. A year after the MPA was implemented, roman catch began to increase. While there was no visible trend in CPUE before the MPA, researchers saw an increase in CPUE in the vicinity of the MPA after its implementation. Other areas further away from the Goukamma MPA exhibited neither positive nor negative effects with respect to CPUE or total catch. The researchers also did not see any increased travel time for fishermen due to the availability of access points to the fishery outside of the MPA.

Figure 1 from Kerwath et al. 2013

Figure 1 from Kerwath et al. 2013

The analysis of fishery data suggests to the researchers that the Goukamma MPA was effective in terms of fishery management and conservation of the roman. Though the exact reasons as to why the MPA was effective have not been investigated, it is believed that spillover and larval export from the MPA are the main contributors to the increase in CPUE around the MPA. When roman inside the MPA are protected, the biomass of the species will increase inside the area until the species has recovered sufficiently. Spillover of adults will occur, as the fish are able to grow without pressure from fishing. After males and females have recovered to pre-exploitation numbers, further CPUE increases can be attributed to recruitment of larval roman. The currents in the area can allow pelagic larvae to stay in the area of the MPA, where they can then settle out, grow and become available to the fishery.

This study gives strong positive evidence for MPA use as a fishery management tool. It provides empirical evidence for fishery recovery without great cost to the local fishermen. This study can be cited as reason to implement MPAs in areas around the world where species similar to the roman are in decline due to exploitation.

 

REFERENCE

Kerwath, S. E., Winker, H., Götz, A., & Attwood, C. G. (2013). Marine protected area improves yield without disadvantaging fishers. Nature Communications, 4, 1–6. doi:10.1038/ncomms3347

 

Plastic ingestion in fish

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By Dani Escontrela, RJD Intern

Plastic debris is becoming a very prevalent problem for our world’s oceans. In fact two of the ocean’s largest features, the North Pacific and North Atlantic Subtropical gyres, have large patches of anthropogenic debris floating in its waters. There has been a significant amount of research that has found plastic or other anthropogenic debris in the stomachs of sea birds, invertebrates, marine mammals and planktivorous fishes. This debris can be harmful to these species as it can lead to physical entanglement, decreased nutrition from intestinal blockage, suffocation and decreased mobility; plastic can also be a vector for other harmful contaminants. As much research as there is about anthropogenic debris ingestion by the species mentioned, there aren’t many studies about ingestion by large marine fishes. This study set out to study this phenomenon by sampling large, pelagic predatory fishes from the central North Pacific subtropical gyre surrounding the Hawaiian Island archipelago.

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Ghostnets: marine debris is “ghostfishing”

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by Emily Rose Nelson, RJD Intern

Annually 640,000 tons of fishing gear is lost, abandoned, or discarded at sea. This deserted fishing gear is known as “ghostnets” and has the potential to “ghostfish” by itself for decades. Ghostnets are a growing issue due to their ability to trap and kill large quantities of commercially valuable fish and threatened species, leading to a loss in food and biodiversity. This waste is of even more concern than other types of marine debris because it is developed specifically to catch marine organisms, often leading to their death.

It is clear there is a lot of trash in the oceans, however little is known about where debris occurs and what organisms it is interacting with. In order to address the problems resulting from ghostnets it is necessary to answer these questions. A team of researchers in Australia set out to understand some of the impacts abandoned fishing gear could have on biodiversity. By combining physical and ecological approaches they were able to predict entanglement risk (expected interactions between nets and turtles) of marine turtles in the Gulf of Carpentaria (GOC) region of Australia.

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Predator identity and its indirect effects on fishing

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By Laura Louon,
Marine conservation student

Few would be surprised by the fact that fishing causes a reduction in the population of the targeted fish. That is a direct effect of fishing. But nothing in the ocean happens in a vacuum; if you decrease the number of individuals of one species, you are bound to see an effect on at least one other species, if not the entirety of the ecological community. When developing holistic management and conservation plans, it is therefore imperative that managers also consider the indirect effects of decreasing the population of a species in an ecosystem as to make the correct decisions. But how do you measure, and hence predict, these indirect effects?

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