Tuna are caught by purse seine vessels and taken alive to cages located close to the coast, were they are fed for months before being exported, mainly to Japan.

Now, why is tuna ranching such a bad idea? Here's 10 very good reasons...

1. Tuna ranching means we are catching even more tuna at a time were fishing pressure should be reduced to allow bluefin tuna to recover;

2. Tuna ranching has expanded above any reasonable level: there is capacity to produce 51,000 tonnes of bluefin tuna in the Mediterranean region (while only a maximum of 32,000 tonnes can be legally caught). This is an undisputable incentive for illegal fishing, as investors will desperately try to make their farms work at the highest level possible to get a return on their high investments;

3. It's out of control: nobody really knows the amount of tuna farmed every year in the Mediterranean (and nobody knows the amount of tuna actually fished);

4. It has made it impossible for scientists to properly assess the state of the bluefin tuna stock, as no accurate information is provided about the amount or size of tuna fished. These are fundamental parameters for them to do their job. If scientists cannot estimate the size of the tuna population they can not determine if the population is decreasing, recovering, or how many fish can be sustainably caught every year;

5. The number of countries and companies involved in tuna fishing and ranching, the complex web of government subsidies and investments, and the extent of trade activities that take place before and after the farming operations make the business of tuna ranching a perfect network to make control virtually impossible: up to 45.000 tonnes of bluefin tuna may have been caught in 2005, well above the legal quota of 32.000;

6. It's a really wasteful activity: up to 25 kg of bait (normally made of fish as sardine, sardinella or anchovy) are needed to get 1 kg of tuna. And bait has to be fished somewhere else: it has been calculated that 225.000 tonnes of fish were thrown to the Mediterranean in 2003 to feed tuna, some of it coming from highly overexploited fisheries;

7. A large percentage of the species used as bait are imported from outside the Mediterranean region. Because the bait is not processed, there is a risk of transmission of diseases to local fish populations. It can affect local stocks of sardines and anchovies;

8. In other cases, concerns have been raised by cetacean specialists that this demand for small fish is leading to the harvest of species that were not commercially fished before. This is the case of round sardinella (Sardinella aurita) in the Alboran Sea (SE Spain), where increasing fishing for this species may put at risk one of the healthiest common dolphin (Delphinus delphis) populations in the Mediterranean

9. Usually tuna ranching cages are located close to shore, coming into conflict with activities such as navigation, artisanal fishing and tourism. Throughout the Mediterranean region, tuna ranchers and purse-seiners are finding themselves in conflict with small scale and traditional fishermen, coastal communities, tourism operators and conservation groups due to the expansion and impacts of their industries;

10. Finally, a few companies are monopolizing access to a common property resource.
Bluefin tuna ranching is resulting in the tuna population being exploited well beyond its limits in order to maximize short-term profits by just a few companies and investors.