CONICET | Buscador de Institutos y Recursos Humanos

This study assesses for the first time the relationship between annual cycles of different biological indices with growth patterns of an marine pejerrey Odontesthes argentinensis population near its southern-distribution boundary in north Patagonia. The reproductive period is between September and November evidenced by an increase of the gonado-somatic index with a peak in October corresponding to the spawning event. The reproductive cycle was also coupled with metabolism processes related to energy allocation as showed by hepato-somatic index and body conditions displayed by changes in the relative somatic index. First size at maturity was 270 and 282 mm for females and male respectively whereas fecundity was estimated at 9380 (± 1797) mature oocytes. Based on marginal increment analysis, most of scales showed a maximum value during the summer, with a sharp decline thereafter during the autumn and winter, indicating that scale rings are formed during the latter period and only once a year. Growth fitted by the von Bertalanffy model for both males and females did not show significant differences and showed a rapid growth during the first two years. The shorter reproductive period compared with the northern O. argentinensis populations inhabiting tropical and subtropical areas was interpreted as an adjustment to temperate environmental conditions. The larger length and size at first maturity are in agreement with the counter gradient hypothesis and could be related to the selective effects of low temperature and a shorter growing season. This latitude dependency argues strongly against the application of the same fishing regulations for different O. argentinensis populations as a whole and reinforces the need to assess basic biological features at a population scale to promote local sustainable fisheries management.

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