Warm bottom water moved the oxygen response of 55 demersal trawl taxa toward higher oxygen on the northern Gulf of Mexico hypoxic shelf in 1982-2025, but the low-oxygen part alone was uncertain

Question: does bottom temperature change how strongly nutrient-driven hypoxia removes demersal taxa from trawl catches? The metabolic index model predicts a temperature sensitivity Eo above 0 eV. Data: 3,330 summer SEAMAP 40-ft shrimp trawl tows (102 cruises, 1982-2025) at 5-50 m depth between 94.5 and 89.0 W, with bottom oxygen, temperature and salinity; 780 tows had less than 2 mg/L oxygen. Method: for 55 common taxa, presence-absence models with cruise fixed effects, depth and temperature splines and a spline of the metabolic index; Eo by profile likelihood; cruise-block bootstrap for all taxa together. Result: the median Eo across taxa was 0.86 eV (95% interval 0.53-1.20); 48 of 55 taxa were above zero and 15 had intervals above zero. The result repeated in four region and period samples (medians 0.64-0.94, all intervals above zero). A parametric null with Eo = 0 gave -0.09 to 0.20, and temperature shuffled within cruises gave 0.07. Nine model checks gave medians from 0.65 to 0.91. A simple hypoxia x temperature term was negative (-0.066 per C, interval -0.119 to -0.017) but did not repeat in the west 1982-2003 sample. Limitations: the estimate uses the full catch-oxygen curve; a post hoc test with only tows below 10 kPa pO2 gave 0.51 (interval -0.04 to 1.07), so a rise of the avoidance threshold alone is not shown. Bottom temperature and depth are strongly related (r = -0.73), trawl absence can mean escape from the net path, and oxygen instruments changed over time. The package has derived tow and catch tables, code, all bootstrap estimates, a simulation check, figures and data provenance.

hypoxia · metabolic index · temperature-dependent hypoxia · Gulf of Mexico · SEAMAP · demersal fish · penaeid shrimp · nutrient pollution · species distribution · dissolved oxygen · climate warming · bottom trawl · observation bias