The Louisiana-Texas shelf is one of the world’s largest areas (up to 22,720 km^2) of seasonal, coastal hypoxia (defined as dissolved oxygen levels less than 2 mg/L). The occurrence and extent of hypoxia have increased over the past century with the increase in nutrient concentrations in the Mississippi River. Hypoxia has negative ecological and economic impacts in the GOM and has been associated with decreased fecundity in Atlantic croaker. The effects of hypoxia on croaker movement and exposure to hypoxia were investigated using the 3D coupled hydrodynamic-water quality FVCOM-WASP model. Movement algorithms were added to the FVCOM particle tracking module to allow fish to move on their own based on environmental conditions. Neighborhood search was the main algorithm used for hypoxia avoidance and had fish evaluate the surrounding area and move away from hypoxic areas. Two random walk algorithms were used to have fish move when not exposed to hypoxia: Random Walk and Cauchy Correlated Random walk. Random walk had fish move by simple diffusion while Cauchy Correlated Random Walk used a biased random walk and had fish favor moving forward as compared to Random Walk. Fish were modeled in both 2D and 3D. Hypoxia exposure was greater for fish that moved only in 2D. Cauchy Correlated Random Walk in 3D resulted in the model fish acting demersal, while the Random walk in 3D resulted in fish staying higher up in the water column.

Modeling 3D fish movement in the Gulf of Mexico hypoxic zone

255th National Meeting (2018)

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