Biological parameters of the common eel (Ophichthus remiger) in the tropical Eastern Pacific: Implications for fisheries management and sustainable conservation

Ophichthus remiger, commonly known as the common eel, is commercially important in Ecuador because Asian markets have high demand. Since industrial fishing began in 2004, no systematic population monitoring has been conducted, limiting understanding of the species' population dynamics and challenging sustainable management efforts. This study provides essential biological parameters of O. remiger in the Gulf of Guayaquil, Ecuador, including size structure, sex ratio, length-weight relationship, and size at first sexual maturity (SFSM), estimated as the median length at sexual maturity (L50). Between August 2013 and December 2014, 17,186 specimens were sampled monthly using bottom longlines and traps. The results indicate a captured length range of 24 to 138 cm, with females comprising 61% of the population among sexed specimens (n = 5,876). Reproductive activity occurs year-round, with peak the gonadosomatic index in October and April. The condition index (K) is not different between females and males, there are no differences in the length-weight relationship; the specimens exhibit allometric growth. The SFSM, expressed as L50, was 56.7 cm for females (95% CI: 56.2-57.2 cm; n = 1,847) and 63.2 cm for males (95% CI: 62.6-63.8 cm; n = 1,109). Based on the estimated size at 50% sexual maturity (L50), minimum capture sizes of approximately 57 cm total length (TL) for females and 63 cm TL for males are recommended as a management reference for O. remiger in the Gulf of Guayaquil. These data provide a robust basis for sustainable management measures, crucial to conserving this high-demand species in international markets.