What do tuna eat in the waters around the Balearics?

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Marc from Mallorca asks: What do tuna eat in the waters around the Balearics?

María Valls Mir, a scientist at Centro Oceanográfico de Baleares, replies.

In general, tuna are opportunistic feeders, which means they eat whatever resources are available. Specifically in the Balearics, there have been feeding studies of Atlantic bluefin tuna in their larval stage during the first 25 days of life (less than 15 mm) which have found that they feed on small crustaceans in plankton, copepods and water fleas, and they are also cannibalistic, eating smaller larvae of Atlantic bluefin tuna and other species of tuna.

We know less about juveniles and adults. There have been detailed feeding studies studies of albacore (Thunnus alalunga) during their reproduction in the islands’ waters, when they eat mesopelagic fish such as barracudinas, lantern fish and small crustaceans that form part of plankton. Mesopelagic fish are species that spend the day in deep, dark waters between 200 and 1000 metres, and come up to the surface to feed at night. The
diet of Atlantic bluefin tuna could be similar to that of albacore.

In other regions of the Western Mediterranean, juvenile and adult Atlantic bluefin tuna feed on mesopelagic fish and crustaceans, but also eat cephalopods such as squid and fish such as sardines and anchovies. Some of the most important feeding zones for Atlantic bluefin tuna are found in the Atlantic Ocean in high altitudes, where they feed on very abundant, oily fish such as herring and mackerel.