Abstract

Relationships between abundance of carangid (jacks) fishes and physical oceanographic features were examined in the northern Gulf of Mexico (GoM). Oceanographic features included mesoscale eddies, the Mississippi River plume and frontal regions where eddies and the river plume intersect, identified by combining satellite and shipboard measurements of temperature, salinity and sea surface height anomaly (SSHA). Generalized additive models where used to explore complex relationships between carangid abundance and physical oceanographic data. Carangid abundance was related to increased temperatures (>28.5°C), decreased salinities (< 32), and low (-10 to 10 cm) to moderate (10 to 30 cm) SSHA, suggesting concentration of fishes at frontal convergence zones between the river plume and mesoscale eddy water masses. The five most abundant carangid species collected were: Selene setapinnis (34%); Caranx crysos (30%); Caranx hippos (10%); Chloroscombrus chrysurus (9%) and Trachurus lathami (8%). Gear-specific differences were identified with a large, dual-warp midwater trawl (LMT) collecting more carangid fishes (86% of the total catch) that were larger (median standard length [SL] = 23 mm) compared to the Multiple Opening and Closing Net and Environmental Sensing System (MOCNESS), which collected fewer (14% of the total catch), smaller (median SL=10 mm) carangids. Results indicate strong links between physical oceanographic features and carangid distribution in the northern GoM, with increased abun-dance occurring in plume and frontal areas that support higher nutrients and productivity.

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