Fishery Production and the Mississippi River Discharge

There is strong circumstantial evidence worldwide that nutrient enriched riverine discharge enhances fishery production on adjacent continental shelves, and this appears to be the case with the Mississippi River where 70–80% of Gulf of Mexico fishery landings come from waters surrounding the Mississippi delta. Two major species groupings, estuarine dependent species (e.g., red drum, Sciaenops ocellatus ; spot, Leiostomus xanthurus ; and Atlantic croaker, Micropogonias undulatus ) and coastal species, (e.g., king mackerel, Scomberomorus calvalla ; Spanish mackerel, Scomberomorus maculatus ; and bluefish, Pomatomus saltatrix ) are most likely to be influenced by riverine discharge. While riverine enhancement of fishery production seems clear, the exact mechanisms through which this occurs are not. Because recruitment makes the greatest contribution to fish stock biomass, it is by enhancing recruitment that fishery production is influenced most. Waters influenced by the river discharge are a rich environment where both physical dynamics, (e.g., hydrodynamic convergence, water column stratification, and transport and retention of fish larvae) and biological dynamics (e.g., primary and secondary production and larval fish production, feeding, growth, and predation) may favor processes that regulate survival and recruitment.