Are captive tuna farms a viable alternative to overfishing?
As originally published August 22nd, 2012 TheEcologist.org
Japanese scientists at Kinki University - based in Osaka, Japan - have unveiled a brand new tuna species, entitled the Kindai Tuna. After three generations of breeding this species is almost identical to its wild cousins, in terms of texture and nutrition, but is the first to be completely nurtured and grown in captivity. However, the process is still expensive and rather inefficient. And the new Kindai tuna sells more, per pound, than wild Bluefin.
In 1982, Japan led the global fishing market with an annual catch of over 11.8 million short tons. The United States followed with an annual catch of 4.3 million. Over the last thirty years these numbers have skyrocketed reaching annual rates of 2 billion tons in Japan and 800 million in the United States. What some may view as advancement and efficiency in the fishing industry, others will deem the result of gluttony and blind consumption. What is undeniable is the adverse environmental impact.
The biggest (and most alarming) impact can be seen in large predatory fish such as the Bluefin Tuna. Although the Pacific Bluefin is not recognised as an endangered species, its dwindling numbers are indicative of a teetering ecological imbalance.
Tuna are carnivorous fish and are one of the top predators in the world’s ocean. They are also one of the most prized catches averaging over $1,000 per pound. Tuna are unique, in that they are endothermic, or warm blooded. They also have a unique metabolism that allows them to continuously and rapidly grow throughout their entire lives. On average an adult tuna may measure up to around 1.8 meters long (6 feet) but can grow upwards to 2.7 meters (9 feet) and weigh over 400 kg (881 lbs.). These massive fish are also incredibly fast swimmers, reaching speeds of up to 40 km/h (25 mph).
Scientists and researchers monitoring the diminishing numbers of tuna are now investigating aquaculture (fish farming) as a viable alternative to large-scale ocean fishing operations. At the moment, about 7% of the global commercial fish harvest is sourced from fish farms. And whilst this is the commonly used term, these operations are frequently not limited to fish. Oysters, clams, crustaceans, and many marine plants are also grown under controlled conditions.
The most common fish species farmed are usually herbivorous, and include catfish, trout, carp, tilapia, and shrimp. However, due to the recent increase in price for fish like tuna, many farmers are looking towards farming larger salt-water fish. These operations are expensive endeavours. Many fish farmers in North America spend more per pound on food than they yield in their finished harvest. Also carnivorous fish, such as salmon and tuna, require a diverse feed made from a wide array of sources in order to maintain the illusion of a natural lifestyle, as well as to promote healthy muscle development.
A bluefin tuna at Monterey Bay Aquarium via nialkennedy, Flickr creative commons.
With the increase in tuna demand, farming the species has garnered a newfound interest. However, because of the tuna’s size and ravenously active lifestyle, many previous attempts to farm them have failed. Maintaining and recreating wild conditions are nearly impossible. Tuna migrate thousands of miles through oceans that vary in chemical composition as well as temperature. This dynamic lifestyle attributes to their high nutritional content and valued taste, but makes captivity a complicated undertaking.
Many other methods have been used to farm tuna. In the past, juvenile fish have been caught and captured. These fish where then fattened until maturity then killed. This method was thought to be effective but now is deemed unsafe because many of the captured fish are never given the opportunity to spawn, further decreasing the wild population.
Many believe that farm raising tuna is the better investment, citing lower mercury content in farm-raised tuna than in wild species. Farm raised tuna have lower levels of mercury but this leads to a different set of ethical and safety issues. Fish farming has raised many of the same ethical questions as large inland cattle and pig operations. Although these fish may one day be cheaper - and contain less mercury – the quality of their farmed life comes under scrutiny because with larger farmed operations, the risk of mistreatment arises. Also, with so many fish living in such close proximity, the threat of disease both for the animals and the consumer drastically increases. Adding to these problems, breeding carnivorous fish demands lots of food, which once again links back to finding a steady and affordable source of fish.