Seals to blame for low cod stocks not over-fishing

The 40,000 strong grey seal population is believed to consume nearly 7,000 tonnes of cod in west coast waters each year. Picture: Bjorn Stefanson
The 40,000 strong grey seal population is believed to consume nearly 7,000 tonnes of cod in west coast waters each year. Picture: Bjorn Stefanson
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Seals rather than fishermen are responsible for low cod stocks along the west coast of Scotland, a report has claimed.

Grey seals are believed to consume nearly 7,000 tonnes of cod each year in the area, where landed catches now amount to only a few hundred tonnes, according to research from the University of Strathclyde.

The recovery plan may not deliver the expected results

Dr Robin Cook

An EU plan to aid recovery of cod stocks placed strict restrictions on the amount of time fishermen can spend at sea as stocks fell to 5 percent of what they were in 1981 but the researchers are now urging a change in the plan.

In some years before the recovery plan was in force, fishing accounted for around 50 percent of the total weight of the cod stock but the study found that, although fishing has now halved, predation by seals has rapidly increased, with the animals eating up more than 40 per cent of the total stock.

The grey seal population has grown since the 1970s, with numbers in the west of Scotland between 30,000 and 40,000.

Cod only makes up around 10 percent of the total weight of fish eaten by seals but still has a significant impact on the stock.

The research, published in the Journal of Applied Ecology, was led by Dr Robin Cook, a senior research fellow in Strathclyde’s department of mathematics and statistics. He said: “In recent years, cod stocks off the west coast of Scotland have declined to barely 5 percent of the value they had in 1981.

“The European Union has introduced a recovery plan to try to curb cod fishing and help the stock recover but there are few signs of improvement off the west of Scotland.

“It appears fishing played a major part in the decline of the cod but increasing predation by seals is preventing the stock from recovering, even though the amount of fishing has reduced.

“Fishery managers face striking a difficult balance.

“With high predation by seals, the cod stock will struggle to improve and the recovery plan may not deliver the expected results. We may have to live with smaller cod stocks if we want to protect our seals.”

Report co-author Dr Steven Holmes of the European Commission Joint Research Centre, said: “Seal populations have increased on the west coast of Scotland and they also seem to be able to find the cod just as easily, even though the stock is now small. This makes the remaining stock very vulnerable to predation.”