Assessing population parameters of four commercially valuable fish species (Actinopterygii) caught by small-scale fisheries in a Mexican Priority Marine Region from the northwestern Pacific

A thorough study of target species, including the collection of data on their life-history traits, is essential for quantitative assessment in fishery management and conservation programs to reduce the vulnerability of populations subject to fishing pressure. This study aimed to analyze the size composition, length–weight relationships, condition factors, and catch volume of four of the most frequent and commercially valuable species caught by small–scale fisheries operating in the Mexican Priority Marine Region 4 of the northwestern Pacific. The presently reported study was based on bycatch from shrimp trawls and commercial catches, and the data were analyzed jointly and separately. Sampling was conducted to obtain length and weight data for four selected fish species: California halibut, Paralichthys californicus (Ayres, 1859); finescale triggerfish, Balistes polylepis Steindachner, 1876; bullseye puffer, Sphoeroides annulatus (Jenyns, 1842); and the spotted sand bass, Paralabrax maculatofasciatus (Steindachner, 1868). A total of 3215 fish individuals were studied, most of which corresponded to the spotted sand bass coming from bycatch. Size-frequency distributions differed among species, with bycatch dominated by smaller size classes and artisanal commercial fisheries capturing larger individuals, reflecting differential ontogenetic habitat use and fishing-gear selectivity. The length–weight parameter b ranged from 2.70 in the bullseye puffer to 2.94 in spotted sand bass, indicating variation among species associated with the presence of both juvenile and adult individuals in the samples; negative allometric growth was consistent across pooled groups, with length increasing proportionally more than biomass. Relative condition factors exceeding 1.0 suggest favorable somatic growth conditions for all species and the capacity to assimilate available energy over extended periods. Size at first capture ( L 50 ) varied among species and groups and differed from published estimates of size at sexual maturity, while S. annulatus and Paralichthys californicus contributed most substantially to total catches during the study period. Overall, this assessment of size composition, length–weight relationships, condition factors, and catch data for the most frequent and commercially valuable species in the Bahía Magdalena–Almejas lagoon system, based on both bycatch and commercial fisheries, provides useful information for evaluating potential fishing impacts and reducing the vulnerability of exploited populations within this marine priority region.