Discards of the NEA cod during bottom trawl fishery in the Barents Sea and adjacent waters in 1983-2002

No abstracts are to be cited without prior reference to the author.

Quantitative assessment of the NEA cod discards during Russian bottom trawl fishery in 1983-2002 was based on database of age readings and length measurements of cod from commercial trawl catches. Reasoning from legislative minimum landing size of cod equal to 42 cm it was assumed that fish of such size are half-discarded back to the sea. Proportion discarded at length was modeled as a logistic curve and used to calculate total cod numbers discarded. Two peaks of discarding in 1987 and 1998 and minimums in 1983-1984 and 1990-1993 were found. The average annual discards were about 6 million cod, which almost corresponded to 6% of total number cod caught. Mainly 3 and 4 year-old cod were subject to discarding. A significant relationship was found between number of cod discarded and abundance of by-caught year-classes, average length of cod from trawl catches as well as national bottom trawl catches.