Abstract
Gulf corvina, Cynoscion othonopterus, is a vital component of commercial fisheries in the northern Gulf of California, but a lack of information on life history parameters have thus far prevented a comprehensive stock assessment. In this project, 530 specimens of Gulf corvina were collected from commercial gill net fisheries in the Colorado River Delta region in Sonora, Mexico, to characterize population structure, age and growth patterns, age and size at sexual maturity and batch fecundity of Gulf corvina. Fish ranged from 145 mm to 1013 mm in total length and from 1 to 8 years of age. Von Bertalanffy growth model parameters were: L<sub>∞</sub>=1006 mm, k = 0.255/yr, t<sub>0</sub> = 0.616 years. Growth rates of Gulf corvina did not differ significantly between sexes, although females were predicted to reach a larger asymptotic length. Mean size (L<sub>m50</sub>) and age (A<sub>m50</sub>) at sexual maturity from histological analyses of gonad tissues was 294.7 mm and 2.3 years for females and 267.5 mm and 2.0 years for males. Maturity estimates from otolith analyses did not differ between sexes and were similar to maturity estimates derived from gonadal histology, indicating that energy allocation shifts from growth to maturation and reproduction after year two. Batch fecundity ranged from 240,394 to 1,219,342 eggs with a mean of 684,293 eggs per spawn, and was correlated to both total length and gonad-free body weight. The distribution of oocyte diameters and oocyte stages indicate that Gulf corvina is a multiple batch spawner with asynchronous oocyte development and indeterminate annual fecundity.
