Modeling the predation dynamics of invasive blue catfish (Ictalurus furcatus) in Chesapeake Bay

Blue catfish (Ictalurus furcatus) have been widely introduced throughout the United States and are invasive in Chesapeake Bay. Despite this proliferation, little is known about the diet of this large, predatory catfish. We used stratified random sampling to collect stomachs from 14,488 blue catfish in Chesapeake Bay. Canonical correspondence analysis (CCA) was used to identify key drivers of the diet of blue catfish, and generalized additive models (GAMs) were used to explore trends in rates of predation by blue catfish on depleted or commercially valuable native species, including American shad (Alosa sapidissima), blueback herring (A. aestivalis), alewife (A. pseudoharengus), American eel (Anguilla rostrata), and blue crab (Callinectes sapidus). Results of CCA reveal that diets were significantly correlated with season, salinity, and total length (TL) of blue catfish, and those from our GAMs reveal the circumstances associated with greater predation on these species. For example, we found that Alosa species were most susceptible to predation by large catfish (>600 mm TL) in freshwater areas during the month of April. This paper describes methods for identifying times, locations, and other circumstances that are associated with maximal predation rates upon certain taxa. The information gained from these approaches can be used to inform management strategies, with the goal of reducing effects of predation on specific organisms.