Are the Temporal Changes Observed in the Reproductive Biology of the Estuarine Conguito Sea Catfish Related to Increased Small-Scale Fishing Effort on the Northwestern Pacific Coast of Mexico?

Biological parameters relating to the reproductive biology of Conguito Sea Catfish Cathorops liropus were investigated in 1979–1984 and 2015–2018 from an estuarine system on the northwestern Pacific coast of Mexico. In the first period, the spawning season occurred during the dry–warm season (April–June), according with the percentage of mature females and the highest gonadosomatic index (GSI) values. Mean TL was 12.3 cm, two cohorts were found, length at maturity was 18.6 cm, and fecundity was 24.47 oocytes/organism. In the second period, the spawning season extended to the rainy–warm season (July–November), as reflected by the percentage of mature females and the GSI values. Mean TL was 11.6 cm, length at maturity decreased to 17.1 cm, and fecundity decreased to 20.67 oocytes/organism, indicating a reduction in the size-based indicators and a change in the spawning period and reproductive effort as time passed. The number of fishing skiffs increased from 1,103 in 1980 to 2,434 in 2019, representing a 220% increase, and the landings increased from 400 to 3,432 metric tons in the same period. Temporal trends in surface water temperature, salinity, and the Oceanic Niño Index did not explain the observed changes between the study periods. These results suggest that the observed changes in the reproductive potential of Conguito Sea Catfish have been at least partially due to fishing.