Bioenergetic strategies contributing to the invasion success of blue catfish

Blue catfish Ictalurus furcatus is an invasive species in many lakes and coastal rivers of the eastern United States. Due to high population densities and negative effects on native species, the potential for blue catfish to invade and colonize aquatic ecosystems is a key management concern. In addition, managers are interested in understanding the efficacy of harvest removals for controlling population sizes of blue catfish in these systems. These issues would benefit from identification of the eco-physiological mechanisms and strategies that contribute to the establishment and spread of this species in novel environments. In this study, we developed a full life-cycle bioenergetics model for blue catfish based on Dynamic Energy Budget (DEB) theory. We found that blue catfish have low maintenance costs but relatively high reserve capacity, two traits that help explain the success of this invasive species. Specifically, blue catfish seem well adapted for life in low and spatially or temporally patchy food conditions, such that individuals can mature and potentially reproduce even when food levels are as low as 13 % of maximum. Blue catfish may thus outcompete native species in many habitats, including those in estuarine systems. Moreover, blue catfish allocate a large fraction (42 %) of assimilated energy towards reproductive processes. Changes in food availability due to competition can have substantial compensatory effects on the age and size at first reproduction, maximum size, and reproduction rates of blue catfish. At seasonal scales, however, the reproductive output of large individuals is relatively insensitive to food availability during the spawning season. Managers seeking to reduce the abundance of the species in estuarine habitats via increased harvest must consider the metabolic capabilities of blue catfish, along with dynamic density-dependent processes that contribute to increased production of blue catfish in response to lower abundances.