Assessment of the reproductive biology of largetooth silverside Chirostoma arge (Atherinopsidae) in Lake Chapala, Mexico

Abstract

Chirostoma arge (Jordan and Snyder, 1899) is a fish endemic to the central plateau of Mexico important for fishing in natural reservoirs such as Lake Chapala. Unfortunately, little is known about this species of the Atherinopsidae family, which is listed as Data Deficient by the IUCN Red List. This study’s objective was to determine the sex ratio, the stage of gonadal maturity in each sex, the spawning season and to estimate the relative condition factor, the minimum standard length and the standard length at first maturity. It analyzed a 3195 fish specimens caught by fishers from six landing sites during an annual cycle. The sex ratio was significantly skewed toward males; however, females recorded a higher mean weight and length than males. Spawning in both sexes began in March and lasted until July. The monthly gonadosomatic index values showed significant increases in females and males from January to May. The monthly variation in condition factor showed a significant increase from November to May. The standard length at first maturity or L50 in females (80.4 mm SL) was slightly greater than in males (77.8 mm SL). The mean fecundity was 1778 eggs (±582 SD). A positive correlation was found between fecundity and ovary weight. This study provides biological and fisheries data on the reproductive activity of one of the most abundant species of silverside, C. arge, in Mexico’s largest lake, Lake Chapala.