Estimates of Food Consumption Rates for Invasive Blue Catfish

Abstract

As a prolific invasive species, Blue Catfish Ictalurus furcatus threaten native organisms in numerous estuarine and tidal freshwaters along the Atlantic coast of the United States. However, no published estimates of consumption rates are available for Blue Catfish in the scientific literature. This information is critical for development of bioenergetics models or estimation of population-level impacts on native species. Using a combination of field and laboratory studies, we provide the first estimates of daily ration, maximum daily ration, and consumption to biomass ratios for Blue Catfish populations. Ad libitum feeding trials conducted in our laboratory reveal that maximum daily ration in Blue Catfish varies by prey type, temperature, and fish size, with maximal feeding occurring in medium-sized Blue Catfish (500-600 mm total length) and at temperatures ≥15°C. Furthermore, estimates of daily ration were higher for fish prey (Gizzard Shad Dorosoma cepedianum) than for crustacean prey (blue crab Callinectes sapidus). Diel feeding chronologies based on field-collected diet samples from 1,226 Blue Catfish demonstrated river-specific variability in daily ration and maximum daily ration. Blue Catfish daily ration ranged between 2.27% and 5.22% bodyweight per 24 h, while maximum daily ration ranges between 8.56% and 9.37% bodyweight per 24 h. Estimates of consumption to biomass ratios varied by river and Blue Catfish size groupings but range between 2.42 and 3.39, which is similar to other benthic omnivores. This research will inform the assessment of predatory impacts of invasive Blue Catfish in the Chesapeake Bay and beyond as it will enable researchers to estimate predatory impacts through the coupling of population models, food habit information, and consumption rate information (current study).

Predatory impacts of invasive Blue Catfish in an Atlantic coast estuary

“…This study was limited in part due to unavailable data inputs. Existing laboratory studies have estimated daily ration for Blue Catfish and supports that temperature influences feeding rates (Schmitt et al 2021). However, temperature ranges examined by existing laboratory studies do not cover the entire thermal spectrum encountered by James River Blue Catfish.…”

“…The data inputs for this analysis have been described in other works (i.e., Schmitt et al 2019c; Schmitt et al 2021; Hilling et al 2023); however, we provide some previously unreported summary statistics to help clarify the inputs and modeling assumptions. In support of Q / B estimation, the parameters of the weight‐at‐age von Bertalanffy model were estimated as W ∞ = 45.46 kg (95% credible interval = 41.51–46.51), k = 0.062/year (0.060–0.065), and t 0 = −0.070 (−0.370 to −0.002) (Figure 2).…”

“…Consequently, we were unable to incorporate seasonal differences in consumption rates and had to assume that consumption of seasonally important prey items were equally weighted. As such, this approach could overestimate consumption of prey species encountered during the winter, when metabolic rates would be lower than much of the year (Volkoff and Rønnestad 2020; Schmitt et al 2021). Blue crab, Dorosoma spp., and White Perch Morone americana were commonly encountered in winter diets but were also observed during other parts of the year (Schmitt et al 2019c).…”

“…We were also unable to account for differences in evacuation rates for different prey types. For instance, crustaceans likely persist in the digestive tract of Blue Catfish longer than soft‐bodied prey (Schmitt et al 2021). As such, estimates of blue crab contributions to diets may be biased high, biasing consumption estimates high also.…”

“…The β parameter was estimated externally based on the length–weight relationship () to aid model convergence and estimation of W ∞ given reported challenges associated with fitting the weight–age relationship (Quinn and Deriso 1999; Hilling et al 2019). Schmitt et al (2021) reported mean annual water temperature (17.23°C) and a mean aspect ratio ( A = 3.74). Given that Blue Catfish in the James River function as omnivores (Schmitt et al 2019c), we substituted 0 for h and d .…”