Abstract

Gag (Mycteroperca microlepis) is one of the grouper species that supports a major commercial fishery in the Yucatan Peninsula and also are creational one in the southeastern United States. In the state of Yucatan it is a very important fishery resource since it represents the third most abundant species in the total catch biomass. Despite its importance, there is scarce informatton in Mexico about its population biology, recruitment, and juvenile period. Therefore, this work is focused on defining the time, age, andsize in which settlement and recruitment take place. During a 19 months survey at the northern coast of Yucatan during 2000 and 2001, 928 gags were caught. All of these were juveniles since they have completed their metamorphosis, lived in a benthic habitat, and were sexuallyimmature. Otoliths microstructure analysis was done using a polishing and etching technique and counting the number of annual rings and daily marks through acompound microscope. In order to authenticate the number and the source of each mark observation, an image analysis with a SEM was carriedout. Two cohorts were established, the first one takes account of individuals of less than a year old displaying several daily and lunar marks, as the second one comprises individuals with two or more years of life, exhibiting two or more annual rings and other source marks. The otolith aging technique points out that recruitment is discontinuous for gag in the Yucatan coast and that the determined nursery areas support more than one annual cohort.

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