STANDARDIZATION OF THE TRAWL FISHING EFFORT IN SANTA CATARINA: THE CASE OF THE SQUID, LOLIGO PLEI, FISHERY

Abstract

A method for standardization of the trawl fishery effort in southern Brazil was investigated from landing records of the squid, Loligo plei, in Itajaí, Santa Catarina (southern Brazil) available from 1989 to 1997. In order to minimize the effect of multispecific trawling effort, squid CPUE (Catch Per Unit of Effort, kg.trip-1) was estimated for landings larger than 500 kg reported in summer only, which presumably had squid as the main target. Standardization of CPUE in each season and among seasons was conducted by the designation of a standard vessel and the estimation of the fishing power of all involved vessels. Standardized CPUE were considerably different from non-standardized CPUE in the seasons of 1992, 1993 and 1994, due to a period of change in the proportion of double rig trawlers and pair trawlers in the fishery. From 1995 onwards the stable proportion of trawler types and a likely improvement of the fishing operations have decreased the effect of effort standardization. Standardized CPUE was found to decrease from 1993 season onwards as a possible consequence of the pair trawler entry in the fishery. The technique was found to be useful to explore information-limited landing records historically available in southern Brazil. Possible violations of the required assumptions, such aas non-constant trip duration, suggest that estimated abundance indices must be regarded with caution.