Biological baseline and population structure of the longfin inshore squid Doryteuthis pealeii in the western Gulf of Mexico

The longfin inshore squid (Doryteuthis pealeii) may represent an ecologically and commercially relevant species in the western Gulf of Mexico, where fisheries are currently dominated by shrimp resources. This study provides the first comprehensive biological assessment of D. pealeii in Mexican waters, based on four exploratory surveys conducted from October 2012 to February 2014. Dorsal mantle length ranged from 49 to 225 mm, and the weight-length relationship indicated negative allometric growth associated with ontogenic changes in body proportions. The sex ratio (F:M = 1.0:0.8) did not vary significantly among surveys or depth strata (χ² = 20.59; df = 12; p > 0.05). Female size at first maturity (L₅₀) was estimated at approximately 115 mm, with seasonal variability (100–156 mm). Mature females where more frequently observed in shallow waters (25–50 m), particularly during autumn, suggesting possible spatial variability associated with reproductive activity. Relative abundance was greatest in the northern region during the same period, coinciding with the higher proportion of mature individuals. These findings establish the first biological baseline for D. pealeii in the western Gulf of Mexico and provide valuable information for future ecological, population dynamics, and fisheries-related assessments in the region. Given the exploratory nature of the sampling design and the temporal limitations of the study, additional long-term monitoring will be necessary to evaluate population variability and potential fishery relevance.