§ Lord Stoddart of Swindonasked Her Majesty's Government:
What is the scientific evidence which demonstrates that species of fish with no swimbladder are killed when caught in demersal trawls, before being discarded under the present minimum landing sizes and discarding rules. [HL680]
§ Lord DonoughueThe main species of fish with no swimbladder discarded from demersal trawl fisheries are flatfish and rays. The majority of discards are below the minimum landing size. Studies on discarding of under-size fish from large commercial beam trawlers in the North Sea indicate that survival varies from 0 to 135WA 50 per cent. in plaice and from 4 to 40 per cent. in sole depending on the tow duration and the condition of the fish landed on deck. The survival rate of rays caught in these fisheries is likely to be similar.
Studies on discarding of plaice by inshore trawlers in the English Channel found survival rates between 65 and 95 per cent. The higher survival compared with large beam trawlers is thought to be caused by slower trawling speeds and smaller catches.
Large numbers of small flatfish are also discarded in small-meshed shrimp fisheries. A number of studies have found survival rates for plaice and sole of more than 50 per cent., with generally lower rates for dabs.