Resumen

PEREZ E, Eduardo P  y  DEFEO, Omar. Estimation of catchability for the Heterocarpus reedi AND Cervimunida johni fisheries in northern Chile, using different catch per unit of area estimators . INCI [online]. 2005, vol.30, n.1, pp.19-23. ISSN 0378-1844.

Catchability coefficients (q) for two shrimp species (Heterocarpus reedi and Cervimunida johni) caught by trawl in Northern Chile fisheries were estimated. An inverse relationship between q and CPUE (catch per unit of effort) has been previously reported for H. reedi, but high values of variance associated to the mean estimates did not permit to assess the relative usefulness of both constant and variable q. No information is available for C. johni. Given the high between-haul variability observed in trawl fisheries, the appropriate way to calculate unbiased estimators for CPUE was evaluated, in order to diminish the variance in q estimators. Five central tendency measures were evaluated: normal, lognormal, Delta, Finney-Sichel, and that calculated from the Central Limit Theorem. To standardize fishing effort, catch was considered per  km² trawled and referred to as catch per unit of area (CPUA). The results indicated that q estimates were reliable, independently of the estimator of the mean employed. However, in terms of precision, estimators of q based on the lognormal distribution were better and are thus suggested as reliable inputs for modeling this trawl fishery in Chile.

Palabras clave : Catchability; Cervimunida johni; Chile; CPUA; Heterocarpus reedi.