Full Length Research Paper
Manuel Gallardo-Cabello, Elain
Abstract
This paper deals with the reproduction of the fish Shortnose Mojarra Diapterus brevirostris of the Pacific coast of Mexico. The fish were captured with gill nets and cast nets and are a common low priced product for local consumption. Its study is important to know the reproduction period and ages of first maturity, to help manage the fishery. The fish were obtained from local commercial fishery from April 2010 to July 2012. Sizes, sex and gonad maturity were registered, gonadosomatic index and condition factors were calculated, as well as fecundity by gravimetric method. The female: male ratio was 1.2: 1. Mature organisms occurred all year round. Sexual maturation (L50) of males and females was observed at a mean size of 14.20 cm and 14.25 cm corresponding to one and two years old, in both cases. First maturity length (L25) was 13.53 cm in males and 13.68 cm in females. The allometric relationship with the hepatosomatic index was LW = 0.0001 · TL2.918 (r2 = 0.417). Condition factor indexes of Fulton, Clark and Safran showed a maximum increment during May and June. The gonadosomatic index showed two high value months: September and February. The mean oocytes diameter was 0.27 mm (range 0.15 to 0.35 mm, standard deviation = 0.044). Fecundity ranged from 16,695 to 807,954 oocytes in females between ages 1 and 6 years old, and mean relative fecundity was 1,877 oocytes·g-1 (513 to 3,683 oocytes·g-1 ). D. brevirostris has an early sexual maturity, its spawning periods are twice a year and has a high fecundity rate, so it can be fished all year round, if its fishing size is over the first maturity length of 14.00 cm. This study is the base line for the fishery management, where the main regulations need to use information on the first maturity size and reproductive season.