Blue Catfish Ictalurus furcatus are native to tributaries of the Mississippi River but are now invasive in several Atlantic slope drainages. This includes subestuaries of the Chesapeake Bay, where their feeding ecology and potential impact on native species was largely unknown. We collected stomach contents from 16,110 Blue Catfish at 698 sites in three large subestuaries of the Chesapeake Bay (James, York, Rappahannock rivers). Cumulative prey curves revealed that sample size was sufficient for diet description, though 1,000 – 1500 stomachs were needed per river. Blue Catfish are opportunistic generalists that feed on a broad array of plant and animal material. Logistic regression models reveal that Blue Catfish undergo significant ontogenetic diet shifts to piscivory at larger sizes (P<0.01) though the lengths at which these shifts occur varies by river system (500 – 900 mm total length; TL). Over 60% of Blue Catfish stomachs contained other invasive species, primarily Hydrilla verticillata and Asian clams Corbicula fluminea. Canonical Correspondence Analysis (CCA) revealed that salinity and season explained the most variation in Blue Catfish diet, while Generalized Additive Models (GAMs) demonstrated that there is considerable spatiotemporal and length-based variation in predation of species of concern. Species of concern include American Shad, American Eel, and river herring, which are imperiled, and blue crab, which support valuable fisheries in Chesapeake Bay. Predation of American Shad, American Eel, and river herring was rare (max predicted occurrence in Blue Catfish diets = 8%), while blue crab was much more common in the diet (max predicted occurrence =28%). Predation of American Shad and river herring peaks in freshwater areas in April, while predation of blue crab peaks in brackish areas in October. Predation of all species of concern is highest for large catfish (500 – 1000 mm TL). Field and laboratory-based estimates of consumption rate revealed that Blue Catfish feed at similar rates as Channel Catfish Ictalurus punctatus, and daily ration is estimated to be 2-5% bodyweight per day during warm temperatures, while peak feeding (maximum daily ration) can approach 10% bodyweight per day. While consumption of imperiled species is rare, Blue Catfish could still have negative impacts on these species due to dense catfish populations. / Ph. D. / Native to the Mississippi River basin, Blue Catfish Ictalurus furcatus are the largest catfish species in North America; they can exceed 100 lbs and live for over 30 years. They were stocked in Chesapeake Bay as a sportfish 40 years ago and are now considered invasive. We performed a series of experiments to describe how invasive Blue Catfish fit in the food web, including diet and consumption rate analyses. Most of the Blue Catfish population is comprised of opportunistic generalists that feed on a diverse array of plant and animal material. We experimentally demonstrated that Blue Catfish tend to feed on whatever species are locally abundant. The most common prey were other species considered invasive in Chesapeake Bay; primarily Asian clams and Hydrilla verticillata, which is an invasive aquatic plant. Blue Catfish also eat other types of vegetation, clams, snails, crabs, fish, small invertebrates, mammals, birds, reptiles, and amphibians. Consumption of imperiled native fishes (like American Shad, American Eel, and river herring) was uncommon while consumption of the commercially-valuable blue crab was common, especially in brackish areas during the autumn. Blue Catfish consumption rates were similar to a closely related species, the channel catfish, and blue catfish can consume an estimated 2 – 5% of their body weight per day during the summer months, and up to 10% of their body weight per day during times of peak feeding. While consumption of imperiled species is rare, Blue Catfish could still have negative impacts on these species due to dense catfish populations
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/83464 |
| Date | 05 June 2018 |
| Creators | Schmitt, Joseph Daniel |
| Contributors | Fish and Wildlife Conservation, Orth, Donald J., Peoples, Brandon Kevin, Jiao, Yan, Castello, Leandro |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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