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Bluefin Tuna. A report by Kyle Hubbard, Kai Qin, and Ann-Germaine Kreger. An Unknown Future. One of the most sought and magnificent fish in the Atlantic, the Bluefin tuna is currently in critical condition due to several decades of ill advised over-fishing.

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bluefin tuna

Bluefin Tuna

A report by Kyle Hubbard, Kai Qin, and Ann-Germaine Kreger

an unknown future
An Unknown Future
  • One of the most sought and magnificent fish in the Atlantic, the Bluefin tuna is currently in critical condition due to several decades of ill advised over-fishing.
  • In fact, the number of Bluefin tuna has decreased by 70% since the 1990s and a staggering 90% since the 1970s. This is a statistically significant figure because this level of population decimation often leads to the failure of species recovery.
  • Without a healthy and viable population in which interaction and frequent breeding can occur, it can be difficult for a species to increase its number. This is compounded by the fact that the sheer unpredictability of the natural world can easily upset a recovering population.
spawning
Spawning
  • Furthermore, unlike many other marine and land animals, Bluefin tuna rely on a single annual breeding period where the Eastern and the Western stocks meet in the Eastern Mediterranean and the Gulf of Mexico.
  • This singular mating opportunity further diminishes the reproduction rate and thus the recovery ability of the Bluefin tuna.
ecological stability
Ecological Stability
  • More unsettling than the dramatic decrease in the Bluefin population, is the evidence of utter disregard for ecological stability on the part of fisheries and law-makers.
  • The ICCAT (International Commission for the Conservation of Atlantic Tuna) considered the mid-1970s Bluefin tuna population to be the MSY (Maximum Sustainable Yield). This essentially dictates that the stability of the tuna population is compromised if it dips below the MSY.
  • However, since the ICCAT announcement, the Bluefin tuna population has dropped an additional 88%. (Figure 1) It is unfortunate that in a few decades, the Bluefin population has plunged from three times the MSY to the brink of extinction.
the depletion of a species
The Depletion of a Species
  • Of the Eastern and Western stocks of the Bluefin tuna, the latter is currently in the more dire condition.
  • In the 1960s, the United States Atlantic Coast was heavily scoured by a massive fishing movement.
  • Numerous purse seiners operated in the Bluefin nurseries and gathered the juveniles to be canned as cat food. (Figure 2)
  • Subsequently, in the 1970s, Japanese longliners further decimated the adult Bluefin in the breeding grounds of the Gulf of Mexico. This two-sided attack was simply too much for the Western stock to handle.
  • Even today, the Western Atlantic population has yet to begin its recovery.
too little too late
Too Little Too Late
  • Upon this realization in the 1990s, the ICCAT set the fishing quota to be 2,830 metric tons for the Western Atlantic population and nearly ten times that amount for the Eastern Atlantic population.
  • Though a belated decree, it is nevertheless a step forward in the preservation of the remaining Bluefin population.
  • However, this quota was issued under the assumption that the Eastern and Western stocks do not interact and that trans-Atlantic migrations are not statistically significant.
intermingling groups
Intermingling Groups
  • A recent study conducted by scientists from Stanford, revealed that the two populations overlapped far more frequently and in larger numbers than previously believed.
  • Using tracking devices on more than 350 specimens, the scientists were able to discover that the western population travels to the feeding waters of Europe and the Eastern Mediterranean.
  • With the continued over-fishing in Eastern Atlantic waters, this new discovery challenges ICCAT’s previous quota. When they travel to the east, Bluefin tuna in the Western Atlantic have a much larger chance of being caught by fisheries.
  • Therefore, the current conservation plan may very well be ineffective and perhaps even harmful to western Bluefin tuna.
biomass of bluefin tuna
Biomass of Bluefin Tuna
  • This failure to meet the standards set by international fishing organization is spurred by many factors such as economic and political pressures.
  • This failure to meet the standards set by international fishing organization is spurred by many factors such as economic and political pressures.
  • Using Microsoft Excel, we extrapolated the equation of a negative exponential model. From our calculations, the biomass of the Bluefin tuna in 2005, will be a horrific 2,850 metric tons.
  • . This is under 5% of the original population present during the 1970s. By 2050, only 45 metric tons will be left. However, we suspect that the Bluefin will be extinct long before that date. A stock size of less than 50 metric tons would be insufficient to maintain a healthy and stable species.
a disastrous future
If the fishing of Bluefin tuna is not discontinued, its extinction will be a heartbreaking inevitability.

Not only would our planet lose one of the most majestic fish in the ocean, but an entire ecosystem and food chain can potentially be disturbed.

It is no doubt a difficult task to immediately halt the harvest of the Bluefin tuna. However, it is undeniably the best course of action for Western and Eastern Atlantic fisheries.

It is the only wise business choice to protect an industry’s capital, which in this case is the population of Bluefin tuna.

A Disastrous Future
aquaculture a beacon of hope
Aquaculture, A Beacon of Hope?
  • Another possible solution is the aquaculture, which is an artificial impoundment used to raise marine fish or shellfish species.
  • This practice, which originated in ancient China, can be used to ease the fishing pressures on the natural fish stock.
  • However, aquacultures produce a great deal of organic wastes which often pollutes the surrounding bodies of water. The organic nutrients such as ammonia and other nitrogen based compounds can potentially lead to toxic algal blooms.
aquaculture cont
Aquaculture (Cont.)
  • Often, aquacultures may not necessarily contain only local fish. This increases the chances of introducing invasive fish species into a stable ecosystem.
  • Along with the spread of new species of fish is the spread of parasites, pests, and certain diseases.Some carnivorous fish farmed in aquacultures require feed made from other smaller fish. For example, the herring is captured to be made into salmon feed. Therefore, some argue that aquaculture may actually increase pressures on over-fishing rather than appease them.
aquaculture potential
Aquaculture Potential
  • Positives of Aquaculture:
  • Aquacultures may greatly reduce the fishing pressures on natural populations such as the Bluefin tuna. It also allows for continued production of fish products to maintain economy and satiate seafood demand.
  • Pollution from aquaculture may be overplayed by some officials. Since polluted waters decrease fish production in aquacultures, these business owners would have an incentive to keep their waters clean.
  • Tuna aquacultures in Australia are a great success as it has tremendously reduced the pressures on the natural tuna populations. Other examples around the world such as Japan and New Zealand further attest to its ecological value.