SCUBA Diving News

Bluefin tuna populations have declined alarmingly over the past few decades due to overfishing fuelled by an increasingly expensive industry.

A new WWF report shows that the international fleets hunting this species to extinction have twice the fishing capacity of current quotas and are netting more than three and a half times the catch levels recommended by scientists to avoid stock collapse.

"WWF's new report uncovers the absurdity of a system long out of control, where hundreds of hi-tech boats are racing to catch a handful of fish," says Dr Sergi Tudela, Head of Fisheries at WWF Mediterranean.

"It is crazy - the numerous new fleets are so modern and costly that fishermen are forced to fish illegally just to survive - and worse still they are fishing themselves out of a job," added Tudela.

To keep fishing capacity within the 2008 legal catch limits imposed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Mediterranean fleet would need to shed 229 vessels - almost a third of the current 617-vessel fleet. Reducing fishing effort to scientifically recommended levels would require the decommissioning of 283 vessels.

WWF is calling on concerned countries to dramatically reduce capacity in this fishery as a matter of urgency ahead of the 2008 fishing season that starts at the end of April.

WWF also urges ICCAT, the body tasked with sustainably managing the fishery, to take a lead in proposing radical solutions. Until the fishery is under control and sustainably managed, WWF continues to advocate a fishing ban - and to applaud responsible retailers, restaurants, chefs and consumer groups who are boycotting Mediterranean bluefin in increasing numbers.

"The fishery is unsustainable in every way - economically, socially, and ecologically. When will the situation be brought under control? The time to act is now - while there are still bluefin tuna to save in the Mediterranean," Tudela concluded.

What can you do? If you want to buy a tin of tuna off the supermarket shelf don’t worry – you almost never find bluefin tuna in a tin. Most tinned tuna is yellowfin or skipjack. If you buy fresh tuna ask your fishmonger whether the tuna is Atlantic bluefin, and whether it comes from the Mediterranean. If it does come from the Med, don't buy it. And at the Japanese restaurant check where they source the Atlantic bluefin tuna. If it is from the Mediterranean, avoid it.

Note: the tuna caught in the Med is called "Atlantic Bluefin Tuna" (Thunnus thynnus). Don't think that because it has the word Atlantic in the name that means it was caught there.

Further Reading:
Bluefin tuna in crisis
Race for the last bluefin: Capacity of the purse seine fleet targeting bluefin tuna in the Mediterranean

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Labels: fish, Mediterranean

Pinna nobilis, the giant bivalve, is endangered. Although in some places it has historically been abundant, there has been a lack of up-to-date information about its exact distribution. SCUBA divers therefore went looking for the giant mussel in the Ionian Sea, Italy.

The results of the study indicate a tentative of recovery of P. nobilis population there, in spite of all the difficulties of a degraded and heavily polluted environment and the damages of illegal fishing methods.

The divers found the pinnids at depths from 3 to 16 m. Their numbers ranged from one individual in 10 hectares, to one every 1.4 hectares. (A hectare is around 2.5 acres or 0.01 square km.)

The survey method employed in this study was non-destructive and relatively simple to perform.

Pinna nobilis lives only in the Mediterranean Sea (which encompasses the Ionian Sea). It likes seagrass meadows and grows up to 120 cm. It sticks up out of the sea bed so is easily seen by divers, once you know what to look for. Although in the Ionian Sea the mussels were found between 3 and 16 m, in other areas of the Med, such as the Adriatic Sea, they live down to 30 m.

In another study, published last month in the Marine Biology journal, Stelios Katsanevakis of the University of Athens investigated the growth and mortality rates of Pinna nobilis in Greece. He found 160 of the mussels and monitored them for 17 months. He discovered that growth rates had a seasonal pattern. The mussels grew slowly during the cold months, and also during August when water temperatures exceeded 29 oC. They grew quickest during late spring and early summer, probably due to an optimum combination of temperature and food availability. Younger individuals grew faster than older ones.

P. nobilis is a protected species in the EU and its fishing is strictly prohibited. However, in the Greek study many deaths were caused by fishing. The mussels were poached exclusively by free-diving and fishing mortality was practically zero at depths below 9 m. Because of this large individuals were restricted to deeper areas.

Journal References:
Environ Monit Assess 2007; 131:339-47.
Marine Biology 2007; DOI: 10.1007/s00227-007-0781-2

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Labels: environment, Greece, Italy, marine biology, Mediterranean, research