Atlantic Bluefin Tuna (Thunnus Thynnus)
Samantha Santoro
"Mediterranean bluefin tuna is collapsing as we speak and yet the fishery will kick off again tomorrow for business as usual. It is absurd and inexcusable to open a fishing season when stocks of the target species are collapsing."
- Dr. Sergi Tudela Head of Fisheries at WWF Mediterranean |
Taxonomy:
Domain: Eukarya Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Perciformes Family: Scombridae Genus: Thunnus Species: thynnus |
Atlantic bluefin tuna (Thunnus thynnus) are remarkable fish of crucial value, with a high selling price on the raw seafood market in Japan. Bluefin tuna are among the largest bony fishes in the ocean reaching lengths of over 10 feet, weights of over 1,200 pounds, and live to be over 30 years (1). The Atlantic Bluefin Tuna has a huge appetite and they will feed as often as they can with their diverse diet. They will consume small fish, squid, eels, and crustaceans. These fish have been known to traverse large migratory distances, such as across the Atlantic and Pacific Oceans (3). The bluefin tuna exhibits the ability to transverse across drastically temperature diverse waters due to its endothermic abilities. These fish are prized catches of both commercial and recreational fishermen worldwide. The historic popularity of fishing for bluefin tuna and their increasing market value have contributed to the exploitation of this species (1).
Atlantic Bluefin Tuna spawn in extremely large groups. This is a very dangerous time for them due to commercial fishing networks. They use boats and even aircraft to identify where those spawning groups are. Then they can capture these fish and yield a huge pay off by selling them (9). Due to the delicious taste of the Atlantic Bluefin Tuna they have been heavily caught in many locations. As a result is illegal to commercially fish them in various areas to help them increase in numbers. Due to the high demand though for this type of fish and the money people will pay for it, illegal hunting of the Atlantic Bluefin Tuna continues to be a very serious problem (10). HELP SAVE THE TUNA!
Atlantic Bluefin Tuna spawn in extremely large groups. This is a very dangerous time for them due to commercial fishing networks. They use boats and even aircraft to identify where those spawning groups are. Then they can capture these fish and yield a huge pay off by selling them (9). Due to the delicious taste of the Atlantic Bluefin Tuna they have been heavily caught in many locations. As a result is illegal to commercially fish them in various areas to help them increase in numbers. Due to the high demand though for this type of fish and the money people will pay for it, illegal hunting of the Atlantic Bluefin Tuna continues to be a very serious problem (10). HELP SAVE THE TUNA!
These fish are known as Thunnus thynnus and have originated from an exothermic ancestor and within 8-10 million years two different species diverged, forming the genus Thunnus. These fish are different from others, they are warm blooded, which is not typical and they can swim in different temperatures of water ranging from cold waters in Iceland to tropical waters in the Mediterranean (1). The system of blood vessels within the tuna are very different, it prevents any heat created through energy being lost to the surroundings, meaning the tuna can swim in water too cold for other fish.
Even though Bluefin tuna tend to stay fairly close to the surface when swimming in the wide open sea, they are capable of diving to depths of 1,000 meters when searching for prey because of their system of blood vessels. The Atlantic Bluefin tuna has two types of muscle; one suited to long-distance, continuous swimming (a Bluefin tuna can cross the Atlantic Ocean in less than 60 days (2), the other providing short, fast bursts of speed (1). They have torpedo shaped bodies making them one of the fastest and largest fishes. The streamline bodies are built for their speed, they can swim up to about 45 miles per hour and the tuna literally means "to rush." (2) They can even retract their dorsal and pectoral fins into slots to reduce drag.
The Bluefin tuna have a beautiful blue and silver-white coloring making them have a camouflage from above and below within the water (4). In fresh specimens, alternating colorless lines and rows of dots can be seen along the lower sides. The first dorsal fin is yellow or blue, the second is red or brown. The anal fins are yellow and edged with black. The central caudal keel is black (5).
In the Atlantic, spawning has been detected in only two areas: the Mediterranean and Gulf of Mexico. This is a limited spawning area compared to other tropical tunas. Spawning in the Gulf of Mexico occurs from April to June and Mediterranean spawning occurs from June to August. Differences in timing could be due to any of a number of factors, such as differing environmental cues or genetic variation (2).
Bluefin are less likely to feed during the spawning season, when the majority of their activity must be dedicated to spawning activities (2). Their major competitors for food are marine mammals and other large fish. Bluefin exhibit different feeding strategies, dependent upon their targeted prey. They have such an enormous size because they are constantly feeding on anything that is smaller than them, this can be anything like filter feeding zooplankton or even swallowing squid, eel, or crustaceans (3). A quick, energetic pursuit is used in obtaining smaller schooling fishes, particularly anchovies, while "modified filter feeding" is used to catch small, slow moving organisms. Marine mammals, including killer whales and pilot whales, feed on the Bluefin tuna. Other predators include sharks, other large predatory fishes, and seabirds (2).
Even though Bluefin tuna tend to stay fairly close to the surface when swimming in the wide open sea, they are capable of diving to depths of 1,000 meters when searching for prey because of their system of blood vessels. The Atlantic Bluefin tuna has two types of muscle; one suited to long-distance, continuous swimming (a Bluefin tuna can cross the Atlantic Ocean in less than 60 days (2), the other providing short, fast bursts of speed (1). They have torpedo shaped bodies making them one of the fastest and largest fishes. The streamline bodies are built for their speed, they can swim up to about 45 miles per hour and the tuna literally means "to rush." (2) They can even retract their dorsal and pectoral fins into slots to reduce drag.
The Bluefin tuna have a beautiful blue and silver-white coloring making them have a camouflage from above and below within the water (4). In fresh specimens, alternating colorless lines and rows of dots can be seen along the lower sides. The first dorsal fin is yellow or blue, the second is red or brown. The anal fins are yellow and edged with black. The central caudal keel is black (5).
In the Atlantic, spawning has been detected in only two areas: the Mediterranean and Gulf of Mexico. This is a limited spawning area compared to other tropical tunas. Spawning in the Gulf of Mexico occurs from April to June and Mediterranean spawning occurs from June to August. Differences in timing could be due to any of a number of factors, such as differing environmental cues or genetic variation (2).
Bluefin are less likely to feed during the spawning season, when the majority of their activity must be dedicated to spawning activities (2). Their major competitors for food are marine mammals and other large fish. Bluefin exhibit different feeding strategies, dependent upon their targeted prey. They have such an enormous size because they are constantly feeding on anything that is smaller than them, this can be anything like filter feeding zooplankton or even swallowing squid, eel, or crustaceans (3). A quick, energetic pursuit is used in obtaining smaller schooling fishes, particularly anchovies, while "modified filter feeding" is used to catch small, slow moving organisms. Marine mammals, including killer whales and pilot whales, feed on the Bluefin tuna. Other predators include sharks, other large predatory fishes, and seabirds (2).
It is important to understand the general trends and any large changes in the history of tuna fisheries as a brief review of the development of tuna of the world. In the nineteenth century, and even ancient times, tuna fishing has been carried out in many places in the world. Most species of tunas are highly migratory, these fisheries caught tunas only at certain points in their life cycle, and this meaning, the fish had to be seasonal (1). These fisheries were local and generally near coasts (2). Industrial fisheries started during the 1940s and 1950s. Major fisheries consisted of Japanese long-liners and bait-boats in the United States. After the Second World War the Japanese tuna fishery expanded its fishing area very rapidly and in the late 1950s reached the Atlantic Ocean (6).
Development of extremely cold storage systems established new frozen products for the sashimi market, which changed the target species. Soon after, speedboats were used to chase the tuna into the net, together with the dolphins. This change in fishing strategy greatly affected the fishing areas and seasons, and the species compositions of catches, including by-catch species (6). For the large-scale long-liners, the Japanese and Korean fleets started to decrease in size, whereas the Taiwanese and "flag of convenience" (FOC) fleets increased rapidly. During this period, regional fishery management organizations introduced many management and regulatory measures for tuna fisheries, which affected fishing patterns and the distribution of catches among countries (7).
More and more management measures have been introduced, and illegal, unreported and unregulated (IUU) fishing practices have increased. IUU fishing became a major problem for the proper management of fisheries resources. In general, tuna-fishing capacity, including IUU vessels, increased extensively during this decade. Recent increases in catches have sometimes caused over-supply to the market. Small-scale long-line fishing increased extensively, while the legal long-line fishing industry started to limit its capacity (7).
Starting in the 1980s, and increasingly in the 1990s, many coastal states, in all oceans, started new tuna fisheries by chartering FOC boats. Some of these vessels changed flag to the coastal state that chartered them, and possibly this tendency will be intensified in the near future. Partially due to the development of these new coastal fisheries, the fishing effort by traditional longline countries started to decline (7).
Fish-aggregating devices (FADs) in the Atlantic in the early 1990s, and this method expanded to the Indian and Pacific Oceans. The FAD fishery is less selective than other fishing modes with regard to the species and size of the fish caught. Fishing efficiency, the size of the fish taken, the species compositions of the catch, and the by-catch of species caught incidentally have all changed drastically with the adoption of this fishing method (8).
In this decade, tuna farming (keeping tuna in captivity for a short time for fattening purposes) started as a new industry (7). This business resulted in increasing price and demand for specific sizes and species of tunas, and hence affected fisheries to a great extent: the relatively small tunas taken by purse seiners that used to be sold only to the canning industry can be now converted to products for the sashimi market. Currently, the main species used in farming is Bluefin tuna, however it is expanding greatly (8).
Development of extremely cold storage systems established new frozen products for the sashimi market, which changed the target species. Soon after, speedboats were used to chase the tuna into the net, together with the dolphins. This change in fishing strategy greatly affected the fishing areas and seasons, and the species compositions of catches, including by-catch species (6). For the large-scale long-liners, the Japanese and Korean fleets started to decrease in size, whereas the Taiwanese and "flag of convenience" (FOC) fleets increased rapidly. During this period, regional fishery management organizations introduced many management and regulatory measures for tuna fisheries, which affected fishing patterns and the distribution of catches among countries (7).
More and more management measures have been introduced, and illegal, unreported and unregulated (IUU) fishing practices have increased. IUU fishing became a major problem for the proper management of fisheries resources. In general, tuna-fishing capacity, including IUU vessels, increased extensively during this decade. Recent increases in catches have sometimes caused over-supply to the market. Small-scale long-line fishing increased extensively, while the legal long-line fishing industry started to limit its capacity (7).
Starting in the 1980s, and increasingly in the 1990s, many coastal states, in all oceans, started new tuna fisheries by chartering FOC boats. Some of these vessels changed flag to the coastal state that chartered them, and possibly this tendency will be intensified in the near future. Partially due to the development of these new coastal fisheries, the fishing effort by traditional longline countries started to decline (7).
Fish-aggregating devices (FADs) in the Atlantic in the early 1990s, and this method expanded to the Indian and Pacific Oceans. The FAD fishery is less selective than other fishing modes with regard to the species and size of the fish caught. Fishing efficiency, the size of the fish taken, the species compositions of the catch, and the by-catch of species caught incidentally have all changed drastically with the adoption of this fishing method (8).
In this decade, tuna farming (keeping tuna in captivity for a short time for fattening purposes) started as a new industry (7). This business resulted in increasing price and demand for specific sizes and species of tunas, and hence affected fisheries to a great extent: the relatively small tunas taken by purse seiners that used to be sold only to the canning industry can be now converted to products for the sashimi market. Currently, the main species used in farming is Bluefin tuna, however it is expanding greatly (8).
In general, Tuna species are within the most commercially valuable fish on earth. Many tuna stocks are fully exploited or overfished and Bluefin tuna are unfortunately delicious and have been eaten by us humans for centuries. Not until the 1970’s did these fish become extremely popular to sushi eaters. In Japan, new ways to capture these quick giants were discovered and with a low reproduction rate and an increase in over fishery the Bluefin tuna had a dramatic decline in their population (1). Overfishing is driving this magnificent fish toward the brink of extinction, and yet many sushi restaurants continue to serve it.
In the last 40 years, Bluefin tuna have declined by 72% in the Eastern Atlantic Ocean, and by 82% in the Western Atlantic Ocean. There are quotas in place to try and prevent overfishing by ICCAT (International Commission for the Conservation of Atlantic Tunas), but that does not stop illegal fishing beyond those quotas (7).
These fish have encountered a very serious problem of being bait to humans. During their time of spawning, the commercial fishing networks have been able to spot these tuna in an extremely large group. The females can produce about 30 million eggs per year, unfortunately only about 1 percent of them will go on to produce more fish. The other 99% of these Bluefin tuna are captured and eaten or sold by humans or become lunch for other predators in the sea. (3) As shown in the graph above, an analysis was done showing that the bluefin breeding population will disappear by 2012 under the current fishing regime. There is such a high demand for these fish that they have become endangered and now illegal fishing for these tuna have become a major problem (3).
The danger of fishing for tuna is not just that they are becoming extinct, but many fishing methods kill other animals during the process as well, this is called by-catch. The equivalent on land would be hunting for deer, but also killing squirrels, birds, bears, and wolves too. Long-line fishing sets out bait hooks at fixed intervals over a fishing line that may be several miles long. While searching for the Bluefin tuna, animals such as seabirds, sea turtles, sharks, dolphins, and whales are caught on these lines too. Those animals either need air to breathe, or must swim constantly to breathe, and they die when caught in these fishing lines (5).
Young Bluefin tuna caught in the Mediterranean are often sent to floating "ranches" where they are held and fattened for up to two years before they are killed, sold, and sent to the market. During this time, they may be bought and sold multiple times before reaching consumers (5). Unfortunately, this complicated supply chain provides an opening for fraud and misreporting, and an opportunity for illegally caught fish to enter the supply chain. Bluefin tuna that is caught and sold must be accompanied by a BCD paper, or Bluefin catch document, that tracks the fish as it moves through the supply chain (4).
Illegal fishing is part of what is referred to as illegal, unreported, and unregular (IUU). This is one of the biggest challenges facing the Mediterranean Bluefin tuna fishery today. The problem in the Mediterranean fishery is that the supply chain is complicated, and profits are high, making fraud and misreporting of catch common. Illegal and unreported fishing not only hurts fishermen operating legally; it also affects the health of Bluefin tuna populations and the direction of future management decisions (8). Scientists use information from catch records to set quotas for fishing seasons. But if catch records are inaccurate, the actual amount of fish killed each year will be incorrect and scientists will be unable to make accurate management recommendations, putting the species at further risk (6).
Unfortunately, Bluefin tuna remains a prized possession on some restaurants menus. The sushi market keeps prices for tuna high, a single tuna sold for a crazy amount at $1.7 million in early 2013, and encourages illegal and unreported fishing. Despite the outrage from concerned people, many sushi restaurants across the globe continue to serve bluefin. Atlantic Bluefin tuna will become extinct if we keep getting fished at current rates (9).
In the last 40 years, Bluefin tuna have declined by 72% in the Eastern Atlantic Ocean, and by 82% in the Western Atlantic Ocean. There are quotas in place to try and prevent overfishing by ICCAT (International Commission for the Conservation of Atlantic Tunas), but that does not stop illegal fishing beyond those quotas (7).
These fish have encountered a very serious problem of being bait to humans. During their time of spawning, the commercial fishing networks have been able to spot these tuna in an extremely large group. The females can produce about 30 million eggs per year, unfortunately only about 1 percent of them will go on to produce more fish. The other 99% of these Bluefin tuna are captured and eaten or sold by humans or become lunch for other predators in the sea. (3) As shown in the graph above, an analysis was done showing that the bluefin breeding population will disappear by 2012 under the current fishing regime. There is such a high demand for these fish that they have become endangered and now illegal fishing for these tuna have become a major problem (3).
The danger of fishing for tuna is not just that they are becoming extinct, but many fishing methods kill other animals during the process as well, this is called by-catch. The equivalent on land would be hunting for deer, but also killing squirrels, birds, bears, and wolves too. Long-line fishing sets out bait hooks at fixed intervals over a fishing line that may be several miles long. While searching for the Bluefin tuna, animals such as seabirds, sea turtles, sharks, dolphins, and whales are caught on these lines too. Those animals either need air to breathe, or must swim constantly to breathe, and they die when caught in these fishing lines (5).
Young Bluefin tuna caught in the Mediterranean are often sent to floating "ranches" where they are held and fattened for up to two years before they are killed, sold, and sent to the market. During this time, they may be bought and sold multiple times before reaching consumers (5). Unfortunately, this complicated supply chain provides an opening for fraud and misreporting, and an opportunity for illegally caught fish to enter the supply chain. Bluefin tuna that is caught and sold must be accompanied by a BCD paper, or Bluefin catch document, that tracks the fish as it moves through the supply chain (4).
Illegal fishing is part of what is referred to as illegal, unreported, and unregular (IUU). This is one of the biggest challenges facing the Mediterranean Bluefin tuna fishery today. The problem in the Mediterranean fishery is that the supply chain is complicated, and profits are high, making fraud and misreporting of catch common. Illegal and unreported fishing not only hurts fishermen operating legally; it also affects the health of Bluefin tuna populations and the direction of future management decisions (8). Scientists use information from catch records to set quotas for fishing seasons. But if catch records are inaccurate, the actual amount of fish killed each year will be incorrect and scientists will be unable to make accurate management recommendations, putting the species at further risk (6).
Unfortunately, Bluefin tuna remains a prized possession on some restaurants menus. The sushi market keeps prices for tuna high, a single tuna sold for a crazy amount at $1.7 million in early 2013, and encourages illegal and unreported fishing. Despite the outrage from concerned people, many sushi restaurants across the globe continue to serve bluefin. Atlantic Bluefin tuna will become extinct if we keep getting fished at current rates (9).
The Mediterranean Bluefin tuna fishery has been under scrutiny for years, due to widespread illegal fishing and historically. Pew is helping to reverse the decline of the Atlantic Bluefin tuna, encourage a sustainable fishing industry, and promote the recovery of this species through three key areas; illegal and unreported fishing of Bluefin tuna, trade, and science (10).
Pew’s Global Tuna Conservation Campaign promotes 23 species of tuna, seven of which are fished commercially. The vessels catch 4.5 million tons of tuna annually are responsible for more hooks and nets in the water than any other fishery in the world. The worldwide and ever increasing demand for tuna has fueled fraud, overfishing and threatens the health and sustainability of many of these species (10).
Pew’s global tuna conservation campaign is urging countries fishing for tuna to do multiple things (10). One accomplishment they would like to complete is to enact strong measures that will lead to the recovery of the severely depleted Atlantic Bluefin tuna population, including the enforcement of science-based catch limits and better tracking of the amount of tuna caught each year. Another is to enact science-based conservation and management measures for other tuna populations in order to ensure healthy tuna populations, protect ocean ecosystems, and ensure the livelihoods of local communities that depend on a healthy marine environment (9).
Strong science and management key to tuna’s survival is to achieve a few goals, Pew is working with governments, other conservation groups, and industry to implement science-based catch limits and improve the quality of data used to manage the fisheries (10). Tuna stocks are fished by dozens of countries, with a significant amount of tuna coming from the high seas, areas that start 200 miles from shore and cover approximately half of the Earth. Their management is largely overseen by Regional Fisheries Management Organizations (RFMOs)—international bodies made up largely of countries that seek to manage fisheries for certain species in specific geographic areas. Pew engages at a number of RFMOs to improve tuna management in the Atlantic and Pacific Oceans (9).
Other improvements being made for the tuna are small projects and petitions that are done through sites and word of mouth. The main ideas of these projects are to change the culture and mind-frame aboard charter and private sport fishing. Small things like blogs can be the start of a huge foundation (9). Simple and easy ways for recreational offshore anglers to practice conservation are in need. There is then a tagging program, all the tag information and data is sent through NOAA's Cooperative Tagging Center which helps inform domestic and international fishery management issues. This program's main goal is to change the culture aboard recreational (charter and private) sport fishing boats to consider tunas as a resource worth protecting. Specifically the program aims to activate the practice of catch, tag and release by allowing anglers free and easy access to tags, tagging gear and education (8).
Pew’s Global Tuna Conservation Campaign promotes 23 species of tuna, seven of which are fished commercially. The vessels catch 4.5 million tons of tuna annually are responsible for more hooks and nets in the water than any other fishery in the world. The worldwide and ever increasing demand for tuna has fueled fraud, overfishing and threatens the health and sustainability of many of these species (10).
Pew’s global tuna conservation campaign is urging countries fishing for tuna to do multiple things (10). One accomplishment they would like to complete is to enact strong measures that will lead to the recovery of the severely depleted Atlantic Bluefin tuna population, including the enforcement of science-based catch limits and better tracking of the amount of tuna caught each year. Another is to enact science-based conservation and management measures for other tuna populations in order to ensure healthy tuna populations, protect ocean ecosystems, and ensure the livelihoods of local communities that depend on a healthy marine environment (9).
Strong science and management key to tuna’s survival is to achieve a few goals, Pew is working with governments, other conservation groups, and industry to implement science-based catch limits and improve the quality of data used to manage the fisheries (10). Tuna stocks are fished by dozens of countries, with a significant amount of tuna coming from the high seas, areas that start 200 miles from shore and cover approximately half of the Earth. Their management is largely overseen by Regional Fisheries Management Organizations (RFMOs)—international bodies made up largely of countries that seek to manage fisheries for certain species in specific geographic areas. Pew engages at a number of RFMOs to improve tuna management in the Atlantic and Pacific Oceans (9).
Other improvements being made for the tuna are small projects and petitions that are done through sites and word of mouth. The main ideas of these projects are to change the culture and mind-frame aboard charter and private sport fishing. Small things like blogs can be the start of a huge foundation (9). Simple and easy ways for recreational offshore anglers to practice conservation are in need. There is then a tagging program, all the tag information and data is sent through NOAA's Cooperative Tagging Center which helps inform domestic and international fishery management issues. This program's main goal is to change the culture aboard recreational (charter and private) sport fishing boats to consider tunas as a resource worth protecting. Specifically the program aims to activate the practice of catch, tag and release by allowing anglers free and easy access to tags, tagging gear and education (8).
1. http://animals.nationalgeographic.com/animals/fish/bluefin-tuna/
2. http://eol.org/pages/223943/details#ecology
3. http://bioexpedition.com/atlantic-bluefin-tuna/
4. http://www.biologicaldiversity.org/species/fish/Atlantic_bluefin_tuna/bluefin_boycott/index.html
5. http://worldwildlife.org/species/bluefin-tuna
6. http://www.forestandbird.org.nz/what-we-do/publications/-best-fish-guide-/southern-bluefin-tuna
7. http://www.nmfs.noaa.gov/ia/iuu/iuu_overview.html
8. http://www.azgfd.gov/w_c/Fish_Tagging_Marking_Techniques.shtml
9. http://ec.europa.eu/fisheries/cfp/international/rfmo/
10. http://www.pewtrusts.org/our_work_detail.aspx?id=146
2. http://eol.org/pages/223943/details#ecology
3. http://bioexpedition.com/atlantic-bluefin-tuna/
4. http://www.biologicaldiversity.org/species/fish/Atlantic_bluefin_tuna/bluefin_boycott/index.html
5. http://worldwildlife.org/species/bluefin-tuna
6. http://www.forestandbird.org.nz/what-we-do/publications/-best-fish-guide-/southern-bluefin-tuna
7. http://www.nmfs.noaa.gov/ia/iuu/iuu_overview.html
8. http://www.azgfd.gov/w_c/Fish_Tagging_Marking_Techniques.shtml
9. http://ec.europa.eu/fisheries/cfp/international/rfmo/
10. http://www.pewtrusts.org/our_work_detail.aspx?id=146