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Dept for Environment Food and Rural Affairs

Answer

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs what the reasons are for the relative decline in cod biomass in the North Sea; and to what extent stocks have been affected by (a) long-term changes in sea temperatures, (b) predation and competition by other fish species, (c) commercial exploitation of food supplies upon which cod stocks rely, (d) seals, (e) overfishing and (f) other factors. [150306] Mr. Bradshaw: Scientists advise that over the last 20 years the fishing rate on cod has been five times that required to promote optimal use of the cod stock, and the fishery captures too many immature fish. On average less than 5 per cent. of each new brood now survives to maturity, and the cod age structure is very restricted. The stock is severely overfished, the biomass of mature fish has shown a prolonged decline, and the number of young cod entering the stock decreased in the mid-1980s. The ICES Advisory Committee on Fishery Management (ACFM) advises that the reduction in recruitment can be at least partly explained by a reduction in the quantity and quality of eggs produced by a reduced spawning stock. There is speculation about the effect of environmental change and species interactions because of increased water temperature, and various contemporaneous changes in other species, but work carried out on these factors does not yet allow them to be quantified. ACFM notes that there may be some changes to the natural mortality of cod, such as a decrease on younger ages, possibly due to reduced cannibalism, and an increase on older ages due to seal predation, but the supporting evidence for these changes is weak.

Secondary information

Type

Written question

Reference

418 c135-6W;418 c133-4W; 150306

Session

2003-04

Subjects

Conservation Fisheries Fish Temperature Seas and oceans Seals North Sea White fish Ecology

Link

View this Written question on www.publications.parliament.uk