Effect of a shore-based sampling program on Notothenia coriiceps populations

The effect of an intensive sampling programme on an inshore population of Notothenia coriiceps was studied at Potter Cove, South Shetland Islands, by comparing catch data taken in successive summers of 1992/93 to 1994/95 at one specific zone (site 1) with those taken in the same last summer at two close but not previously sampled zones (sites 2 and 3). The fish were caught with trammel nets under similar sampling conditions (depth, net measurements, bottom type). In site 1, a marked decrease in length (TL) of the fish was observed throughout the whole period. The fish from sites 2 (x=32.4 cm) and 3 (x=31.8 cm) exhibited no significant differences in mean length. They were significantly larger than those from site 1 caught in the summers of 1994/95 (x=28.8 cm) and 1993/94 (x=30.2 cm), but were similar in size to those sampled in the summer of 1992/93 (x=31.7 cm), just when the sampling programme started in site 1. Present results show that the size variations of N. coriiceps observed at Potter Cove were not due to a natural decrease of the proportion of larger fish in the population, but related to an intensive sampling effort carried out at one specific site.