Defense Date

2007

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Dr. Michael L. Fine

Abstract

Catfish pectoral spines are an anti-predator defense mechanism. They can be bound or locked, making the fish harder to swallow, or used to produce distress calls by rubbing ridges on the dorsal process against a channel in the wall of the pectoral girdle. Growth of the pectoral spine and girdle were examined in relation to fish size within and across species that occur throughout central and eastern Virginia. These included blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), white catfish (Ameiurus catus), brown bullheads (Ameiurus nebulosus), yellow bullheads (Ameiurus natalis), flathead catfish (Pylodictis olivaris), margined madtom (Noturus insignis), and tadpole madtom (Noturus gyrinus).Pectoral spines and girdles grow as catfish increase in size. In larger species spine length and weight increase nonlinearly with fish size, suggesting that maintaining spine dimensions becomes less important in bigger individuals less likely to suffer predation. The incidence of spine breakage also increases in larger fish. In smaller species spine length increases linearly in our samples (brown and yellow bullheads and margined and tadpole madtoms). In all species spine width increases linearly with total length. The spine base (dorsal process width and depth and dorsal-ventral length) grows linearly with total length in most species. However, measurements of the spine base increase nonlinearly in white catfishes, and dorsal process width increases nonlinearly in wild channel catfish although the increase was linear in cultured channel catfish.Girdle depth increased linearly with total length in all species except for wild channel catfish, and the ratio of coracoid to cleithrum depth varied among species. Pectoral girdle weight increased linearly with fish weight in blue catfish, cultured channel catfish, brown bullheads, and margined and tadpole madtoms. However, girdle weight, a major component of the body, increased nonlinearly in wild channel, white, yellow bullheads, and flathead catfishes. Cultured channel catfish had smaller pectoral spines and girdles than wild channels, a likely epigenetic response to predators. Catfish spines were identified to species, allowing determination of catfishes eaten by bald eagles (Haliaeetus leucocephalus) using spines collected near their nests. Bald eagles ate blue catfish (60%), channel catfish (27%), white catfish (9%), brown bullheads (4%) and yellow bullheads (0.5%). Madtom and flathead catfish were not consumed. Mean sizes captured were: Blue catfish (366 mm, 414 g), channel catfish (417 mm, 618 g), white catfish (320 mm, 591 g), brown bullheads (278 mm, 277 g) and yellow bullhead (203 mm, 192 g).

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

June 2008

Included in

Biology Commons

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