Population analysis of smallmouth silverside, Chirostoma chapalae Jordan & Snyder, 1899 (Atherinopsidae), an endemic fish in Lake Chapala, Mexico

A sample was analyzed of 1,129 specimens of Chirostoma chapalae from Lake Chapala, Mexico obtained from catches of local fishers between October 2016 and September 2017. Size frequency, length-weight relationships (LWRs), growth, mortality, exploitation rate, survival rate, and relative condition index were estimated. The LWRs showed negative allometric growth in females (b = 2.735) and isometric growth in males (b = 3.000). The SL_∞ was 9.20 cm in females and 8.94 cm in males, and the growth coefficient k ranged from 1.80 year⁻¹ to 1.90 year⁻¹, and the t₀ from 0.119 to 0.113. Estimated total mortality (Z = 3.20 year⁻¹), natural mortality (M = 1.56 year⁻¹), and fishing mortality (F = 1.64 year⁻¹) values were higher in females. C. chapalae is at optimum, underexploited levels according to the exploitation rate (E = 0.42 year⁻¹). The SL at first capture (SLp_c) was 65.8 mm and the SL at retention (SLp_r) of the fishing gear was 62.4 mm. This indicates that more than 50% of the fish caught enter the fishery at a larger size. The condition factor (Kn) showed body robustness in fall and subsequent spawning from spring onwards. Our findings contribute to the future development of fisheries management strategies in the largest lake in Mexico.