Bluefin Tuna

From GEOG397 Topics
Jump to: navigation, search

Contents

Introduction

Figure 1. Bluefin Tuna swimming in large schools

Bluefin Tuna are found all over the world and are highly sought after commercially as well as for recreation. Bluefin comprises of three different species; the Atlantic, the Pacific and the Southern Bluefin. All three species have been over-fished for decades. They are caught and killed to fuel an unsustainable trade. A single fish can fetch over a million dollars on the Japanese market. Earlier in the 2013, at the Tsukiji fish market in Tokyo a specimen sold for 155 million yen (approximately $1.7 million) <ref name= Westlake> Westlake,A. 2013. Single Bluefin Tuna sells for record 1.7 million at Tsukiji fish market. Japan Daily Press. http://japandailypress.com/single-bluefin-tuna-sells-for-record-1-7-million-at-tsukiji-fish-market-0720908/</ref>. Bluefin Tuna stocks have been a highly topical debate in recent years, with many concerned that the relentless pressure on the species may result in Bluefin surpassing its sustainable threshold resulting in another Unique species wiped from our plant. The following page is dedicate to introducing the three Bluefin species, its current state of existence as well as indicators, pressures and consequence and finally the management processes and responses of people which hope to help maintain the sustainability of a truly special resource.

Figure 2. Distribution and Spawning locations of Atlantic Bluefin Tuna <ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>

Atlantic Bluefin Tuna (Thunnus thynnus)

The Atlantic Bluefin Tuna is the giant of the Bluefin species. It is found predominantly in the Eastern Atlantic Ocean from Norway to the Canary Islands', it is also know to migrate almost as far down as the Bottom of Africa<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>. The species is also found in the Mediterranean Sea and the Black Sea. However its abundance within the Black Sea has dropped dramatically due to changing environmental conditions over the last few decades <ref name= IUCN>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21860/0</ref>. The Atlantic Bluefin Tuna is also found in the Western Atlantic from Canada down to Brazil, although the bulk of the population found off Brazil has deteriorated so much so that accounts of the Tuna off the Brazilian coast have not been recorded for decades <ref name= IUCN>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21860/0</ref>. The distribution of the Atlantic Bluefin is clearly shown in Figure 2<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>. The Atlantic Bluefin Tuna is primarily a oceanic species however has been known to travel seasonally closer in to shore. It is a pelagic species, spending its time in the top proportion of the water column, close to the surface. It is highly migratory and can tolerate a wide range of temperatures. The species schools by size and preys on smaller schooling fish and squid as well as crabs and other bottom dwelling species. <ref name= IUCN>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21860/0</ref> The life expectancy of the Atlantic Bluefin can range from 35-50 years<ref name= IUCN>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21860/0</ref>. Sexual maturity for Western Atlantic Bluefin is first reached at around 9-13 years, when it is approximately 145kg.<ref name= IUCN>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21860/0</ref> However for Eastern Atlantic Bluefin sexual maturity is reach much earlier when the species is only 3-5 years old and around 25kg <ref name= IUCN>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21860/0</ref>. Spawning for the Western Atlantic stock occurs in the Gulf of Mexico from April to June. The Eastern Atlantic stocks spawn in the Mediterranean Sea from May to August<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>. The current world rod and reel all-tackle record as determined by the International Game Fishing Association (IGFA) for the Atlantic Bluefin Tuna is 678.58kg, caught out of Nova Scotia, Canada in October 1979<ref name=IGFA>International Game Fishing Association. http://wrec.igfa.org/WRecSearchList.aspx?lc=AllTackle</ref>.

Figure 3. Distribution and Spawning locations of Pacific Bluefin Tuna<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>

Pacific Bluefin Tuna (Thunnus orientalis)

The Pacific Bluefin Tuna is located throughout the Indo-Pacific Ocean as seen in Figure 3 <ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>. It is predominantly a temperate to tropical species however it has been recorded to be found as far south as French Polynesia and New Zealand, thus showcasing its ability to tolerate a wide range of temperatures <ref name=IUCN2>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/170341/0</ref>. The Pacific Bluefin Tuna, like it relatives the Southern and Atlantic Bluefin is primarily a oceanic species however has been known to seasonally travel closer in to shore. It is also a pelagic species. It is an a dominant predator, feeding on schooling fish and squid as well as occasionally feasting on crabs and other bottom dwelling species <ref name=IUCN2>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/170341/0</ref>. The life expectancy of a Pacific Bluefin can range from 15-26 years. Sexual maturity is first reached when the species is approximately 5 years old, or when it is around 150cm in length and about 60 kg <ref name=IUCN2>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/170341/0</ref>. Spawning occurs between Japan and the Philippines between April and August also shown in Figure 3<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>. The current world rod and reel all-tackle record as determined by the IGFA for the Pacific Bluefin Tuna is 335.37kg, caught in 2012 in Houhora, New Zealand.<ref name=IGFA>International Game Fishing Association. http://wrec.igfa.org/WRecSearchList.aspx?lc=AllTackle</ref>.

Figure 4.Distribution and Spawning Location of Southern Bluefin Tuna<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>

Southern Bluefin Tuna (Thunnus maccoyii)

The Southern Bluefin Tuna is found throughout the Indian, Atlantic and Pacific Oceans as seen in Figure 4<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>. Unlike the its very similar relatives the Atlantic and Pacific Bluefin, it spends the majority of its time colder southern waters, primarily between 30⁰ South and 50⁰ South, however the species has been well-known to visit waters as far North as 10⁰ South and as far south 60⁰ South.<ref name=IUCN3>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21858/0 </ref> The Southern Bluefin Tuna is an oceanic species, it spends the bulk of its life out at sea visiting the coast line very few times. It is a pelagic species spending the majority of the time within the top proportion the water column. It is an opportunistic predator, feeding on a wide variety of schooling fish and squid, different types of plankton as well as many types of bottom dwelling species such as crabs, crayfish, octopus etc<ref name=IUCN3>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21858/0 </ref>. The life expectancy of the Southern Bluefin is around 20-40 years. Sexual maturity is reached at about 8-10 years old, when fin length is approximately 120-130 cm<ref name=IUCN3>The IUCN Red List of Threatened Species. http://www.iucnredlist.org/details/21858/0 </ref>. Spawning occurs in a fairly small area in the Indian Ocean off the North-Western coast of Australia from around September/October through to March, this is also shown in Figure 4<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref>. The current world rod and reel, all-tackle record as determined by the IGFA for the Southern Bluefin Tuna is 167.5kg, caught off Tathra, Australia in July 2009 <ref name=IGFA>International Game Fishing Association. http://wrec.igfa.org/WRecSearchList.aspx?lc=AllTackle</ref>.

Fishery History

Fishing for Bluefin Tuna has existed in certain areas for centuries. In the Mediterranean large scale capture of Bluefin has been a means of survival for many. In the Mediterranean the oldest known large scale method is the use of tuna traps, these were set nets near the coast which focused on spawning migration patterns. The majority of nets were set to catch tuna on arrival to their spawning grounds however some were set months after to catch departing tuna<ref name=Mather>Mather, F. Mason, J. Jones, A. 1995. life history and fisheries of the atlantic Bluefin Tuna. U.S Department of Commerce. National Oceanic and Atmospheric Administration. National Marine Fisheries Service.</ref>. Harpoon and hand line fishing has also been around for centuries in certain areas, however taking a very minimal portion of the stock. Pre-World War Two methods of capture had not changed very much, stocks were not over-fished and the species was sustainable. However following World War Two fishing significantly expanded, The beginning of the end in many people's eyes. The introduction of live-baiting, long-lining and closed bottom nets (Purse Seines) meant fishing could occur year round and catch numbers increased. By 1956 Japanese long-lines had become a dominant force in the Atlantic. By 1969 Japanese long-lining had expanded so much so that most waters between 40⁰ North and 40⁰ South were covered<ref name=Mather>Mather, F. Mason, J. Jones, A. 1995. life history and fisheries of the atlantic Bluefin Tuna. U.S Department of Commerce. National Oceanic and Atmospheric Administration. National Marine Fisheries Service.</ref>. Bluefin tuna are still fished intensively today as well as captured live to be placed in farms to grow. Year to year catch reports vary significantly, some express drastically declining populations others show and stable stock.

Current State

An assessment carried out in 2012 by the International Commission for the Conservation of Atlantic Tunas (ICCAT) has shown that the Western Atlantic Tuna Spawning Stock Biomass (SSB) had steadily declined from the early 1970s to 1992 as seen graphed in Figure 5. However since then, with significant variance year to year the SSB has gradually increased<ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref>. On The other hand however, the Eastern Atlantic Bluefin SSB peaked in the early 1950's and again in the early 1970's. The SSB has then proceeded to significantly decline, almost halving by the mid 2000's also shown graphed in Figure 5.<ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref>.

Figure 5. The right graph indicates SSB (by kg) of Bluefin Tuna in the Eastern Atlantic, the Blue line shows reported and the red indicates inflated rates. The left graph shows SSB of Bluefin Tuna in the Western Atlantic <ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref>

Assessments carried out by the International Scientific Committee for Tuna and Tuna like Species in the North Pacific Ocean evaluated that the Pacific Bluefin Tuna stock is over-fished and SSB has declined significantly in the last decade, reaching its lowest levels as seen in Figure 6.<ref name=ISC>International Scientific Committee for Tuna and Tuna like Species in the North Pacific Ocean http://isc.ac.affrc.go.jp/pdf/Stock_assessment/Final_Assessment_Summary_PBF.pdf - isc pacific </ref>.

Figure 6. Shows the absolute and the realative SSB of Pacific Bluefin Tuna <ref name=ISC>International Scientific Committee for Tuna and Tuna like Species in the North Pacific Ocean http://isc.ac.affrc.go.jp/pdf/Stock_assessment/Final_Assessment_Summary_PBF.pdf - isc pacific </ref>.

An assessment of the of the Southern Bluefin Tuna stocks carried out by the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) in 2011 showed that SSB had reduced to very low levels, levels below the maximum sustainable yield as graphed in figure 7.<ref name=CCSBT>Commission for the Conservation of Southern Bluefin Tuna (CCSBT)http://www.iccat.int/Documents/SCRS/ExecSum/BFT_EN.pdf- iccat atlantic </ref>.

Figure 7. Shows the SSB for Southern BLuefin Tuna for the base case, showing the medians, quartiles and 90th percentiles, together with reference points of 20% of pre- exploitation spawning stock biomass <ref name=CCSBT>Commission for the Conservation of Southern Bluefin Tuna (CCSBT)http://www.iccat.int/Documents/SCRS/ExecSum/BFT_EN.pdf- iccat atlantic </ref>.

From the above statements, from some creditable organisation it is easy to establish that, yes Bluefin Tuna stocks are under a great deal of stress with the majority of spawning stocks in declined and still declining significantly over time in some circumstances .

Indicators of State

Figure 8: WWF Bluefin Tuna Tracking <ref name=WWF> WWF. http://mediterranean.panda.org/about/marine/bluefin_tuna/science_in_action/tag_track/ </ref>

Spawning Stock Biomass

Bluefin tuna have been massively fished for decades, leaving their population declining because of the irresponsible nature of the industry. Indicators for Bluefin tuna are limited and variably subject to misleading information. The individual organisations that monitor the different types of Bluefin tuna provide stock assessments of their respective fish. The spawning stock biomass graphs above are the best representation of current/future stock available.<ref name=WWF> WWF. The plunder of bluefin tuna in the Mediterranean and East Atlantic in 2004 and 2005 Uncovering the real story. http://awsassets.panda.org/downloads/wwfbftreportfinaleditionreducido_final.pdf </ref> Scientists are able to predict where and when Bluefin tuna will be spawning as their habitat requirements are relatively exact. With the constant oceanographic data from weather buoys and satellites, scientists are able to use this to help calculate spawning stock biomass.<ref name=Dailey> Science Dailey. Spawning Habitat of Bluefin Tuna in Gulf of Mexico: Critical Area Intersects Deepwater Horizon Oil Spill. http://www.sciencedaily.com/releases/2010/05/100528210726.htm </ref> Catch data is much more variable as it is reliant on the accurate data from fisheries that are motivated by high profits and bound by quotas. Illegal activities undertaken by fisheries is common place and WWF believe that deliberate understating of catch numbers happens frequently in order to stay under the defined quota.<ref name=WWF> WWF. The plunder of bluefin tuna in the Mediterranean and East Atlantic in 2004 and 2005 Uncovering the real story. http://awsassets.panda.org/downloads/wwfbftreportfinaleditionreducido_final.pdf </ref> This extremely lucrative market is causing this misleading information which will mean that we do not really know the extent of the damage the fishing is doing and extinction to one or more of these species could happen sooner than expected.

Some researchers believe that there is issues with the conservation organisation stocks for instance, the International Commission for the Conservation of Atlantic Tuna (Iccat). Researchers suggest that the stock for, the eastern and western Atlantic populations of bluefin, are in fact less for both as fish have been known to swim between provinces, providing inaccurate data. This is just an example of the many loose ties in the understanding and data for Bluefin Tuna.<ref name=Smith> Smith L. Bluefin tuna monitoring is flawed, say scientists. http://www.fish2fork.com/news-index/Bluefin-tuna-monitoring-is-flawed-say-scientists.aspx </ref>

Tagging

Tagging and monitoring of Bluefin tuna is a good way of finding out the status, whereabouts and weight of a tuna.<ref name=WWF> WWF. http://mediterranean.panda.org/about/marine/bluefin_tuna/science_in_action/tag_track/ </ref> The WWF provides the public with the ability to track the movements of certain Bluefin tuna (seen in figure 8), but more importantly on their data base they will know when a tagged fish is caught and potentially if it has made it to a farm or has been slaughtered. Far more management needs to be in place when dealing with fisheries and quotas. The reason illegal activity is happening so frequently is that there is not enough stock check up by officials to warrant fear of being caught. Increased involvement from 3rd party groups would be a good way to see fishing quotas followed.

Pressures

Figure 9: Japans Bluefin Catch from 1956-2007 <ref name=Sonu> Sonu S. BLUEFIN TUNA SUPPLY, DEMAND, AND MARKET OF JAPAN. http://swr.nmfs.noaa.gov/fmd/sunee/bluefin.pdf </ref>

The thriving nature of the bluefin fisheries and the declining population of bluefin species is directly correlated to the high demand for consumption. The giant fish is a highly sought after product in Japan, with 80% of the fish caught in the Mediterranean ending up here. Estimates are that, close to 50% of global Bluefin consumption is by the Japanese, with the rest made up from various European and Asian countries. <ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref>

Bluefin Tuna Sashimi <ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref>

Japanese Involvement

The Japanese love sea food, with close to a quarter of their total imports being sea food, it is notably their greatest edible import. With the country importing enough of it for each citizen to consume 70 kilos per year, it is not surprising that bluefin tuna imports and consumption are substantially higher, in Japan, than any other country.<ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref> Japan is also catching a huge amount of bluefin tuna each year. Mitsubishi Japan deals with almost half of the world’s bluefin tuna market, freezing 20,000 tonnes each year which it claims they use to even the market when catches are down.<ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref> This type of activity can be seen as preparation for the extinction of bluefin which will give Mitsubishi a monopoly on bluefin sales. Looking at figure 9 it is obvious that catches are down from the peak in the late 50’s to recent times and it is not due to lack of fishing but lack of fish. Estimates are that bluefin numbers have dropped up to 90% since 1970.<ref name=PEW> PEW. The story of Atlantic Bluefin Tuna. http://www.pewenvironment.org/news-room/fact-sheets/the-story-of-atlantic-bluefin-tuna-85899420680 </ref> What’s motivating this excessive fishing and massive declining population is the high demand for the bluefin tuna in sushi, and sashimi (thinly cut portions of raw fish). Bluefin tuna, which is commonly called Maguro in Japan, is considered the panicle of sushi fish and is usually the highest priced item on the menu in sushi bars and restaurants.<ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref> From the 1960s onwards, refrigerating technology enabled fish to be shipped great distances. This began the craze for bluefin tuna in Japan although only the very wealthy could afford to dine on the socially deemed exquisite delicacy. The fact that the fish was so expensive and eaten by the rich meant that more and more people wanted it and when the establishment of bluefin tuna farms was introduced and the increase in supply from other countries, it bought the price down and all Japanese could finally afford the delicacy.<ref name=WWF> WWF. Overexploited for its value. http://mediterranean.panda.org/about/marine/bluefin_tuna/overexploited_for_its_value/ </ref>

Sushi Sashimi

Japan is crazy about sushi and sashimi, it is one of the most desired of foods and Bluefin Tuna is the highest quality of ingredient. The Japanese are not wasteful and use as much of the fish as possible. Akimi is the most standard form of Maguro (Bluefin tuna) which consists of cuts from the middle and side of the fish and is served when no specifications are made. Otoro, which is cut from the very undersides of the fish is the most expensive due to the meats high fat content, it allegedly melts in your mouth upon consumption (according to sushi connoisseurs). Lastly Chutoro, which lies between Akimi and Otoro which is preferred by some for its lower fat content. Maguro is almost always served in sushi rolls with soy sauce and wasabi or raw.<ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref>

Bluefin Tuna Farm, Croatia <ref name=Phillips> Phillips T. Truth Behind Bluefin Fish Farming. http://www.globalanimal.org/2012/07/19/truth-behind-bluefin-fish-farming/78424/ </ref>

Bluefin Tuna Farms

Bluefin Tuna farming is a relatively new phenomenon which began in the late 1990’s. The farms are basically a fattening pen where tuna are kept until they are a desired size to sell on the market.<ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref> Fleets use large nets which are able to capture schools of young bluefin and transfer them to the ocean pens. Once here they are fed, an unsustainably large amount of baitfish, for just under a year where they average an increase in size of around 10 times their initial body weight.<ref name=Phillips> Phillips T. Truth Behind Bluefin Fish Farming. http://www.globalanimal.org/2012/07/19/truth-behind-bluefin-fish-farming/78424/ </ref> The first farm arose in the Mediterranean in 1996 and now there are more than 70 registered farms, with speculations of illegal operations operating to the side. This type of activity is even further bad news for the Bluefin as young tuna which would not sell on the market now can be kept till they are ripe. As all Bluefin species reach sexual maturity comparatively late, they often do not get the chance to spawn in the wild meaning many fish are not even reproducing once in their life, drastically affecting the population. Reproduction in tuna farms is, for arguments sake, impossible as conditions simply just do not allow it.<ref name=Werf> Der Werf, W. factSOn the bluefin tuna and damaging fiShing OperatiOnS in the mediterranean. http://www.seashepherd.org/images/stories/blue-rage/homepage/crew_briefing_document.pdf </ref> A very recent rule was implemented in 2010 meaning that no Mediterranean Bluefin tuna could be caught weighing less than 30 kg, aimed at allowing spawning. This was a sign of positive movements towards sustaining, although it was soon changed allowing Croatia exemption providing no tuna below 30 kg was put in farms. Soon after it became evident that juveniles were being framed by Croatia still, but with very little monitoring systems in place for farming, nothing can be done.<ref name=Phillips> Phillips T. Truth Behind Bluefin Fish Farming. http://www.globalanimal.org/2012/07/19/truth-behind-bluefin-fish-farming/78424/ </ref>

Consequences

Food Chain of Bluefin Tuna <ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref>

Extinction of Adults

Bluefin Tuna is an apex predator so plays a pivotal role in keeping the natural balance of the ocean. By removing an animal (especially a predator) from the food chain, a ‘trophic cascade’ can occur. <ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref>.This collapse of a species starts a domino effect that is felt right throughout the ecosystem. As Bluefins are near the top, all animals below it can grow without being hunted, fundamentally changing the nature of the ocean. A subsequent population increase in sardines, squid, crustaceans and other smaller carnivores. This unchecked population would over exert the herbivores below, henceforth creating an unbalanced, unsustainable food chain.

In the instance that Bluefin Tuna does collapse, scientists believe that there may be a steep increase of bentopelagic cephalopods, such as squid. As a result, the sardines that are hunted by squid would be negatively affected. However, in contrast, other small pelagic fish such as the sardinelle and horse mackerel would thrive with the removal of one of their major predators.<ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref>


Historical Example

Collapse of a species due to overfishing has been seen in many places worldwide. Perhaps one of the most severe was the overfishing and decline of ground fish species, such as cod and haddock in the Northwestern Atlantic. <ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref> The subsequent collapse cod stocks from overfishing meant that the cod was replaced by shrimps, crabs and lobsters. In turn, this lead to an unbalanced ecosystem and the now dominant shrimps, crabs and lobsters overhunting the animals below them on the food chain.

Role of Juveniles

Although, Bluefin tuna is obviously vital to the top of the food chain, it is also important to the bottom. The diet of a young Bluefin Tuna is predominantly plankton and other microscopic algae and animals living at or around the surface of the ocean. These minute organisms feed on bits of dead plant and fish matter along with sunlight and the runoff from human sewage and industrial waste <ref name=Ponds>Ponds, A. 2010. BlueFin Tuna are now an Endangered Species. NaturalNews.com http://www.naturalnews.com/029383_tuna_endangered_species.html#</ref>. ] Toxins and metals accumulate in the micro-plankton which then are passed onto the juvenile tuna and enriched through their lives and into the diets of humans and other predators of the tuna.

Risk to Humans

As young tuna grow into fully sized adults, the toxin and metal levels can reach dangerous levels. Possibly the most dangerous of these is mercury, as it can result in neurological problems such as Minamata disease. <ref name=Werf>Werf, W. (2010) Bluefin Bonanza: Facts on the Bluefin tuna and damaging fishing operations in the Mediterranean. Written for Sea Shepherd Conservation Society. Available from http//www.seashepherd.org</ref>. An independent study carried out in the US found that the much of the Bluefin Tuna purchased at restaurants and supermarkets contains mercury levels that are well above safe limits of consumption. <ref name=Werf>Werf, W. (2010) Bluefin Bonanza: Facts on the Bluefin tuna and damaging fishing operations in the Mediterranean. Written for Sea Shepherd Conservation Society. Available from http//www.seashepherd.org</ref>.

Historical decline of Atlantic Cod

Economical

Additional to the ecological damage there is serious economic and social consequences. By overfishing Bluefin tuna in an unsustainable manner, many peoples livelihoods will be lost. Direct and indirect job losses will impact families, economies and the global market. Currently, tuna fishing in Mediterranean is viewed under the assumption that if they don't take the last tuna then someone else will.<ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref> The problem is compounded with too many large boats catching too few fish, leading to illegal fishing and an unsustainable fishery. Due to declining stocks, illegal harvest has become a central factor in the economic equation. If the fishing fleets only took the legal limit (128-tonne quota per vessel) the net loss for each vessel would 224,000 euros per year.<ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref> Therefore, the current limits force fishermen into overfishing and illegal catches, inevitably resulting in stock and economic collapse. Upon collapse, fishermen will be without jobs and entire families and communities will go under. Those most sensitive are the approximately 1,000 traditional Spanish and Moroccan fishermen that depend on tuna trapping. The Spanish government estimates that for every job in the tuna trap fishery, there are three additional jobs in the processing and trade sector. <ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref>

Historical Example

When the Canada suspended North Atlantic Cod fishing in 1992, 40,000 fishermen and other workers became unemployed. This cost the Canadian government more than $4 billion (Canadian dollars) over a 20-year period in job and revenue losses. <ref name=WWF> WWF Briefing: Mediterranean bluefin tuna – the consequences of collapse. http://awsassets.panda.org/downloads/onthebrinktunacollapse.pdf</ref>

Management & Responses

Atlantic Stocks of Bluefin needed to reach sustainability <ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref>

Due to the large range of migration and habits, the management and response to the collapse of Bluefin Tuna is a complicated issue. Because of this, the problem has been broadly split into 3 different areas that are dependant on the species at risk. Alike many large pelagic, or open ocean, fish, Bluefin Tuna is managed by the regional fisheries management organizations (RFMOs).<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref> These RFMOs assign the rules and regulations that member countries can agree regarding the conservation and management of the tuna. The implementation of these measures occurs at the country level. There are four major RFMOs currently opperating; the Commission for the Conservation of Southern Bluefin Tuna (CCSBT), the Inter-American Tropical Tuna commission (IATTC), the International Commission for the Conservation of Atlantic Tunas (ICCAT) and the Western and Central Pacific Fisheries Commission (WCPFC). These organisations employ a selection of scientists and specialists to advise them on trends, stocks and sustainability of the Bluefin. However, the ultimate decision on national and overall quotas, size limits, and other management decisions are not made by these people but rather representatives of the member States who make up the RFMOs commission.<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref> Because the commission only asks the scientific committees advice, (which it can follow or decide not to) there is a danger in the commision setting regulations that are in the best interests of their country and not the sustainability of the Bluefin.

Atlantic Bluefin

Historically, this region has been divided into eastern and western sectors due to differences in catch and life histories, treating them as separate populations.<ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref> However, recent studies have found that the eastern and western Atlantic populations are reproductively separate but overlap through migration. It is now understood that up to 50 percent of the fish in some regions of the Western Atlantic having originated in the Eastern Atlantic <ref name=Boustany> Boustnay, A.M., C.A. Reeb, and B.A. Block. 2008. Mitochondrial DNA and electronic tracking reveal population structure of Atlantic bluefin tuna (Thunnus thynnus). Marine Biology 156(1): 13–24.</ref> Because of this new information, the management of western atlantic bluefin has changed drastically as even small changes in the number migrating from east (much larger stock) to west will greatly influence the stock counts.<ref name=ICCAT>International Commission for the Conservation of Atlantic Tunas (ICCAT). 2010. Report of the 2010 Atlantic Bluefin Tuna Stock Assessment Session. Madrid, Sept. 6–12, 2010. ICCAT Collected Volume of Scientific Papers 66(2): 505–714</ref>. The greatest problems in the management of bluefin tuna in the atlantic, is the compliance with management regulations. Due to higher quotas than scientific guidance and even lack of compliance with these quotas, sustainable catches have been exceed by up to 400 percent some years <ref name=Hurry> Hurry, G.D., M. Hayashi, and J.J. Maguire. 2008. Report of the independent review. September 2008. PLE-106/2008. ICCAT, Madrid.</ref> To try and halt a collapse, the commission established a total allowable catch at 13,500 t and 12,900 t in 2010, 2011 and 2012, respectively.<ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref> To accompany these limits, the commission stated that is need to establish a three-year recovery plan for 2011-2013 with the goal of achieving BMSY (Biomass corresponding to maximum sustainable yield) through 2022 with at least 60% of probability <ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref>. Although a more extreme mangament response than cutting quotas, the Atlantic Bluefin could be put on the endangered list which would prohibit international trade for commercial purposes. <ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref> Due to the majority of Atlantic tuna, bound for global sashimi markets, this listing would significantly reduce the forces driving it into a collapse.

Proscribed quotas for the Southern Bluefin <ref name= CCBST> Commission for the Conservation of Southern Bluefin Tuna (CCSBT). 2012. Report of the Seventeenth Meeting of the Scientific Committee </ref>

Pacific Bluefin

As the Pacific Bluefin is a temperate fish it fell through the cracks of RFMOs, meaning that it has not been managed by quotas and catch monitoring for as long as the other species.<ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref>This is because the main tuna fisheries in the Pacific have been yellowfin, bigeye, albacore, and skipjack, so thus been the focus of management. Currently, more than 90 percent of Pacific bluefin caught are juveniles and the spawning grounds are beeing targeted <ref name=Bard> Bard, D. 2013 New Scientific show Pacific Tuna population down 96.4%. Global Tuna Conservation. http://www.pewenvironment.org/news-room/other-resources/new-scientific-report-shows-pacific-bluefin-tuna-population-down-964-percent-85899441247 </ref> To prevent this continual decline, the major countries (Japan, Mexico, South Korea, and the United States) need to immediately inforce conservation measures. Such regulations should include; science-based catch limits, size limits implemented and banning fishing on bluefin spawning grounds. <ref name=Bard> Bard, D. 2013 New Scientific show Pacific Tuna population down 96.4%. Global Tuna Conservation. http://www.pewenvironment.org/news-room/other-resources/new-scientific-report-shows-pacific-bluefin-tuna-population-down-964-percent-85899441247 </ref> Additionally, each member of the pacific needs a specific quota, stop the carry-forward of unused quota, size limits and an effective monitoring program with an enforcement process. This would include; electronic tracking from catch to sale, require observers on fishing vessels, monitor tuna ranches and implement fishing bans on members or fleets that do not report catch data.<ref name=Bard> Bard, D. 2013 Policy Statement: Pacific Bluefin Management. Global Tuna Conservation. http://www.pewenvironment.org/news-room/fact-sheets/policy-statement-pacific-bluefin-tuna-management-85899469968 </ref>

Southern Bluefin

There has been a quota system since 1982 as a result of declining stocks seen in Australia, New Zealand and Japan. <ref name=Edwards> Edwards, M. 2001. Progress and problems: The operation of the convention for the conservation of southern bluefin tuna. In: K. Hinman (Ed.), Getting ahead of the curve: Conserving the Pacific Ocean’s tunas, billfishes, and sharks. National Coalition for Marine Conservation, Leesburg, Va. </ref> However, other fishing countries began to target the Bluefin and although the CCSBT put strict quotas in the population continued to decline. <ref name= CCBST> Commission for the Conservation of Southern Bluefin Tuna (CCSBT). 2010. Report of the Fifteenth Meeting of the Scientific Committee. September 11, 2010, Narita, Japan. </ref> To try and manage this problem South Korea Indonesia, Taiwan and China joined the commission along with additional countries added as cooperating nonmembers (cannot vote but ad-hear to quotas).<ref name= CCBST> Commission for the Conservation of Southern Bluefin Tuna (CCSBT). 2010. Report of the Fifteenth Meeting of the Scientific Committee. September 11, 2010, Narita, Japan. </ref> However, the under-reporting of catches has meant that tuna stocks have continued to decline to the current state. These recent limits to manage and restrict quotas are more server for member governments that had overfished in the past to allow the Bluefin to rebuild its population over time <ref name= CCBST> Commission for the Conservation of Southern Bluefin Tuna (CCSBT). 2010. Report of the Fifteenth Meeting of the Scientific Committee. September 11, 2010, Narita, Japan. </ref>. However, because the Southern Bluefin has a long life span and reproduces late in its life, this rebuild to sustainable numbers will be slow and fragile. <ref name=Boustnay> Boustnay,A. 2011. Bluefin Tunas, The State of the Science. The PEW Environment Group, Ocean Science Series. http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/Pew-BluefinTunaScienceCompendium-Oct2011.pdf</ref> This is a dangerous process for the Bluefin, as it only takes a small amount of illegal activity or miss-management by the members to decimate the remaining 3-4%.

Historical Example

Although the current outlook is bleak for the Bluefin Tuna, a recent success story does exist. Due to similar pressures currently facing the Bluefin; overfishing, large catches of juveniles and fishing on spawning grounds the North Atlantic swordfish population collapsed. It rapidly decreased 1980 and 2000, but with the cutting of quotas, legal sizes and closed areas to protect juvinles and spawning adaults the population has started to increase. <ref name=ICCAT> International Commission for the Conservation of Atlantic Tunas (ICCAT)http://www.ccsbt.org/site/recent_assessment.php</ref> This should be seen as a framework to which the Bluefin Tuna can follow and hopefully recover

Conclusion

In conclusion, the Bluefin Tuna species are incredible important. They have been fished for centuries all over the world. They are a vital food source for many and sustain a number of opportunities for thousands of people directly and indirectly.they play crucial role in an ever change ecosystem. Stocks have been over-fished now for decades. Pressures of the Japanese markets are a huge driver in influencing the downward spiral for many stocks. Without coming up with a means to sustain the species and enforcing rules and regulations surrounding the Bluefin Tuna species, it does face a very dark future with the prospect of extinction a very real outcome.

References

<references />