Environmental Drivers of Jumbo Squid During Fishery Collapse in the Gulf of California (2019–2024)

ABSTRACT The jumbo squid ( Dosidicus gigas ) is a cephalopod endemic to the eastern Pacific with significant ecological and economic importance. Its exploitation in the Gulf of California (GC) peaked in the 1990s, with catches exceeding 100,000 tons, but collapsed in 2009 and virtually disappeared by 2015, largely due to environmental changes and overfishing. Between 2019 and 2024, research cruises were conducted to evaluate fishery resources in northwestern Mexico. During these expeditions, the presence of jumbo squid in the GC was documented, and catch per unit effort (CPUE, kg/h) and mantle length (ML, mm) were analyzed in relation to in situ environmental variables using generalized additive models (GAMs). Results indicated that the highest biomass occurred at salinities below 35, with elevated dissolved oxygen concentrations (> 200 μmol/kg −1 ) and warm temperatures (~24°C). Size analysis revealed that mantle length was greatest at lower salinities (< 35.2), suggesting that squid distribution is linked to specific thermohaline conditions and water masses that provide optimal habitat. This study represents the first documented instance of jumbo squid captured with midwater trawls in the GC. Since sampling was conducted at 15 m depth during nighttime, results likely reflect surface foraging behavior rather than the species' full vertical range, underscoring the importance of considering diel vertical migration. Few squids were found in historically exploited fishing grounds, where changes in thermohaline structure and oxygen levels were evident. In contrast, higher biomass concentrations at the mouth of the GC coincided with more stable environmental conditions. These findings highlight the sensitivity of D. gigas to oceanographic variability and suggest broader ecological implications for resident populations and regional fisheries.