Theses and Dissertations


Title: Biological control of a trematode disease of bluegill

Name: Avault, Jr James William

Degree: MS

Chair: Dr. Ray Allison

Resides: FAA Library

University: Auburn

Location: Auburn, Alabama

Date: 1963

Pages: 37

Keywords: Trematode,Disease,Bluegill,Biological Control.

Abstract:

An investigation was begun on July 1, 1962 to determine the potential of snails infected with cercariae of Posthodiplostomum minimum in producing infection in bluegills. Infected snails, in aluminum wire baskets, were stocked into plastic-lined pools at rates of 1 or 5 per pool. The baskets were checked daily for dead snails. All dead snails were replaced with infected ones. Bluegills of 2 sizes, 1-inch or 3-inch, were stocked into the pools. All bluegills were exposed to cercariae for 24 days at which time the experiment was terminated and quantitative counts were made of the parasites found in each fish. One-inch bluegills contained an average of 20 parasites per fish when exposed to cercariae from 1 infected snail and 37 parasites per fish when exposed to cercariae from 5 infected snails. Three-inch bluegills contained an average of 110 parasites per fish when exposed to cercariae from 1 infected snail and 200 parasites per fish when exposed to cercariae from 5 infected snails. Comparison of treatment means revealed that the intensity of infection was related more to the size of the fish than to the number of infected snails to which the bluegills were exposed. An investigation was begun on October 10, 1962 to determine the effectiveness of the shellcracker in reducing infection of P. minimum in bluegills through the destruction of the snail host. Infected snails were stocked free into plastic-lined pools at rates of 1, 5 or 10 per pool. Parasite-free snails were also stocked into all of the pools so that each pool contained a combined total of 100 snails. Bluegills were stocked into all the pools. Some pools were stocked with shellcrackers, whle others received no shellcrackers and were held as controls. One-half of the pools that received shellcrackers contained vegetation. All bluegills were exposed to cercariae for 37 days at which time the experiment was terminated and quantitative counts were made of the parasites found in each fish. When stocked alone with 1, 5 or 10 infected snails, bluegills average respectively 38, 83.4 and 114.6 parasites per fish. In pools stocked with shellcrackers, bluegills contained an average of 16.4, 16.0 and 48.1 parasites per fish. In the presence of shellcrackers and vegetation, bluegills contained an average of 6.7, 9.3 and 32.9 parasites. Comparison of treatment means revealed that the shellcracker was effective in significantly reducing infection of P. minimum in bluegills, and that the presence of aquatic vegetation did not reduce the effectiveness of the shellcracker.

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