Bluefin Tuna

Figure 1: Bluefin Tuna, jumping through the water. (Photo Source: http://www.worldwildlife.org/species/bluefin-tuna)

 

Bluefin Tuna are one of the largest vertebrates and can currently be found on the endangered species list.  They can live to be 40 years old, and can grow to be 1000 lbs (Walsh, 2013).  In the wild Bluefin Tuna are the top of their food chain, with almost no predators (except humans).  Generally these tuna are split into two categories, the eastern and the western Bluefin Tuna.      

The main reason for the Bluefin Tuna being on the endangered species list is because of overfishing.  There are a few reasons why the Bluefin Tuna is so sought after.  First, is the fact that the tuna is so large.  Second is the fact that the tuna is a very tasty fish, which many people look for and order at restaurants.  Finally there is the fact that the Bluefin Tuna goes for a lot of money, mainly being bought by sushi restaurants.  This tuna generally goes for about $15000, however the most expensive fish in 2013 was $1.76 million.  This large amount of money for each fish, causes for there to be greater incentive for fisherman to go out and catch them. 

Certain reports in 2013 showed that the population of Bluefin Tuna had decreased by nearly 96%.  Even though this number has increased slightly since then, the population of Bluefin Tuna is still only at about 50% of its past population number from 1970 (CBC News, 2014).  This major decline occurred before a quota was put into place.  However, this quota has been hard to calculate due to little data on the migration and movement patterns of the Bluefin Tuna (World Wildlife Fund). 

A study done by Cosgrove et al. in 2014 tried to get better information on the movement patterns of the tuna, and thus help the government produce a better fishing quota.  Within this research they tagged certain tuna, and followed their movements and recorded the data they collected.  The research found that the tuna dove to different depths at different times of the year.  These depths were consistent with all of the tuna who were tagged.  Knowing the depth at which the tuna will be at certain times of the year would allow for researchers to be able to accurately calculate the population of the Bluefin, and thus allow them to accurately calculate a quota.           

There is a few considerations that must be taken by the government in order for the quota to work, and for the recovery of the Bluefin Tuna.  First, they must consider the Bluefin “ranches” (Heffernan, 2014).  These are certain tuna farms, which raise Bluefin Tuna until they have become fattened, by nearly 20%.  Generally the tuna that are taken and placed into these farms are very young, immature tuna.  This affects the reproductive success of the tuna by removing the ones which are able to reproduce and pass on their genes.  The next consideration that must be taken into account is illegal fishing.  Within the fishing quota every place has their own percentage of the quota they can catch legally (Figure 2).  Most of the tuna that are caught are not reported and thus are not considered when looking at what the current quota should be.  There is also the idea among fisherman to declare a lie (say you only brought in the quota) even if you brought in more. This would allow for the fisherman to continue fishing, thus making more money.  The last consideration is the Bluefin tuna’s migration pattern.  Through recent satellite studies it has been found that both western and eastern Bluefin Tuna migrate within the same area (Safina and Klinger, 2008).  However, when caught they are not counted as two separate entities even though there are two different quotas (one for the western tuna and one for the eastern tuna).  This is mostly an important consideration when it comes to the western tuna.  Since this is the more endangered tuna, if they are caught on the eastern side (and counted toward the eastern side) then the western population will decline whether the fisherman follow the quota or not.     

Figure 2: The quotas for different countries in 2013. (Photo Source:http://www.sciencedirect.com.ezproxy.tru.ca/science/article/pii/S0308597X14001444?)

 

I believe that future research is needed in order to make sure the recovery of the Bluefin Tuna continue.  Research is needed in order to better understand the migration patterns of these tuna, as well as the government taking into consideration illegal fishing and tuna “ranches” when making up the fishing quotas. 

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Citations:

Cosgrove, Ronan; Arregui, Igor; Arrizabalaga, Haritz; Goni, Nicolas; and Sheridan, Michael.  [Internet]  2014.  New insights to behavior of North Atlantic albacore tuna (Thunnus alalunga) observed with pop-up satellite archival tags.  Fisheries Research, 150: 89-99  [Cited February 3, 2016]  Available from: http://www.sciencedirect.com/science/article/pii/S0165783613002403? DOI: 10.1016/j.fishres.2013.10.013

Heffernan, Joseph Paul.  [Internet]  2014.  Dealing with Mediterranean Bluefin tuna: A study in international environmental management.  Marine Policy, 50: 81-88 [Cited February 3, 2016] Available from: http://www.sciencedirect.com.ezproxy.tru.ca/science/article/pii/S0308597X14001444?  DOI: 10.1016/j.marpol.2014.05.014

Safina, Carl; and Klinger, Dane H.  [Internet]  2008.  Collapse of Bluefin Tuna in the Western Atlantic.  Conservation Biology, 22: 243-246 [Cited February 3, 2016]  DOI: 10.111/j.1523-1739.2008.00901

CBC News.  [Internet]  Bluefin tuna catch limits increased to 2,000 tonnes for 2015.  [Cited February 3, 2016]  Available from: http://www.cbc.ca/news/canada/nova-scotia/bluefin-tuna-catch-limits-increased-to-2-000-tonnes-for-2015-1.2837862

Walsh, Bryan.  [Internet]  2013.  The Pacific Bluefin Tuna is Going, Going…  [Cited February 3, 2016]  Available from: http://science.time.com/2013/01/11/the-pacific-bluefin-tuna-is-almost-gone/

World Wildlife Fund.  [Internet]  Bluefin Tuna.  [Cited February 3, 2016]  Available from: http://www.worldwildlife.org/species/bluefin-tuna