MORTALITY OF FISH FROM THE BY-CATCH OF SHRIMP VESSELS IN THE NORTH-SEA

The results from 3 different programmes concerning by-catch mortality in shrimp fisheries are reported. Mortalities increased considerably after the catch passed the sorting sieve. 100% mortality was detected for whiting (Merlangius merlangus). Mortalities were about 10% for sculpin (Myxocephalus scorpius), hooknose (Agonus cataphractus), and eelpout (Zoarces viviparus) in the discard fraction. Survival of flatfish depended strongly on the species, the size of the specimens as well as the catch and catch processing conditions, and ranged from 17 to 100%. No differences could be detected in the survival after sorting on different machines. However, due to better sorting efficiency, the rotary sieve may reduce mortality of fish in the by-catch.