DIFFERENCES AMONG BASIC BIOLOGICAL PARAMETERS IN A POPULATION OF CHOKKA SQUID LOLIGO-VULGARIS REYNAUDII (CEPHALOPODA, LOLIGINIDAE) SAMPLED BY 3 METHODS

A large, discrete aggregation of squid was sampled at short intervals by means of jigging, midwater trawling and purse-seining. Differences among basic biological parameters of the population (e.g. length frequ ency) indicate that jigging is a more selective, and therefore biased, method of sampling than midwater trawling or purse-seining. This has important consequences for stock assessments that take commercial catc hes into account. The selectivity curve indicates that squid of mantle lengths (ML) 28-33 cm are over-represented (in terms of the situation in the population) in fisheries conducted by jigging and that squid < 26 and >34 cm ML are under-represented if purse-seine results are cons idered to be representative of the population.