Age, growth, and mortality of the spotted rose snapper Lutjanus guttatus from the southeastern Gulf of California

The age of the spotted rose snapper Lutjanus guttatus over the continental shelf of the southeastern Gulf of California was estimated by examining transverse sections of their sagittal otoliths. Individuals (238) collected from summer 2001 to spring 2003 were analyzed. Ages were assigned based on counts of alternating opaque and translucent zones (annuli). The consistency of the readings showed that the otolith increments could be used for age determination. The maximum observed age was 11 years corresponding to a female of 48.5 cm total length and 1500 g weight. Significant differences in growth between the genders in observed length-at-age were not found. The von Bertalanffy growth parameters were L-t = 66.19(1 - e(-0.13(r-0.23))). The instantaneous rate of total mortality (Z) estimated from catch-at-age data was 0.353, the fishing mortality was estimated to be 0.153 and the optimum rate of fishing mortality was estimated to be 0.0999. Therefore, the population of L. guttatus in the Gulf of California is exploited above optimum levels. Because this is a species with a low growth rate, the population of L. guttatus in the Gulf of California requires prudent management. Furthermore, fishery managers need to consider as part of any harvest strategy for these fish the preservation of significant levels of the spawning stock by reducing the numbers of juvenile fish captured in the shrimp trawls and for sale in the market. (C) 2005 Elsevier B.V. All rights reserved.