2025/07/01 by Mary C. Fabrizio, Troy D. Tuckey, Jack R. Buchanan +1 · 1 voice
Environmental Science · #Marine and fisheries research #Crustacean biology and ecology #Fish Ecology and Management Studies
paper · pdf · doi:10.1093/mcfafs/vtaf025
openalex publication_date 2025/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
ABSTRACT Objective Year-round predation of invasive Blue Catfish Ictalurus furcatus on native blue crabs Callinectes sapidus was characterized and quantified from estuarine habitats (0–18 psu) in the James River, a tributary of Chesapeake Bay. We also quantified encounter rates between predator and prey using an index of spatial overlap in the distribution of the two species. Methods Monthly gill-net samples of Blue Catfish collected from the lower James River between August 2018 and June 2020 provided information on diet composition, from which the probability of predation on blue crabs was estimated. The local index of collocation was estimated for 1996–2023 using catch data from a bottom trawl survey in the James River; annual changes in the index were modeled using a segmented regression. Results Year-round predation occurred primarily on juvenile blue crabs (<90 mm carapace width), indicating a size refuge for larger crabs. Large (≥501-mm fork length [FL]) Blue Catfish were 1.68 times more likely to consume blue crabs than intermediate-size (301–500-mm FL) fish and 8.19 times more likely to consume blue crabs than small (200–300-mm FL) Blue Catfish. Predation likelihoods were greater for Blue Catfish from the down-estuary region. Between 2018 and 2020, an estimated 564,365 (95% CI = 58,065–948,372) juvenile blue crabs were removed annually through predation by Blue Catfish from the lower James River. Predator–prey encounter rates throughout the James River increased significantly between 1996 and 2009 and stabilized thereafter. Conclusions The overall predation impact of Blue Catfish reflected the relative abundance of Blue Catfish size-classes: Intermediate-size fish consumed a greater number of blue crabs because of the relatively large number of this size-class in the population. We hypothesized that the down-estuary region may facilitate predation by aggregating prey in structured areas that are readily exploited by novel predators.