Theses and Dissertations


Title: Dynamics of a fish population subjected to intensive harvesting

Name: Elrod, Joseph Harrison

Degree: MS

Chair: Dr. H. S. Swingle

Resides: FAA Library

University: Auburn

Location: Auburn, Alabama

Date: 1966

Pages: 82

Keywords: Pond management,Balance,Bass,Bluegill,Micropterus salmoides,Lepomis macrochirus.

Abstract:

A heavy withdrawal of fish in the first season of fishing a new largemouth bass - sunfish - catfish population was followed by an overcrowding of small bluegills. Failure of young-of-the-year largemouth bass to control the late summer spawn of bluegills led to the overcrowding. The unbalanced condition persisted through the next two years with a low yield to fishermen in both years. Schnable and Petersen estimates of the largemouth bass population in October were too low for older fish but provided good estimates of young-of-the-year bass. Survival of bass was estimated to be 27.7 per cent per year. A major part of deaths may occur in winter and natural mortality may not occur in a pattern described by the instantaneous concept for a year at the same rate. Probability paper was not satisfactory for separating age groups of bass. A high density of intermediate-sized bluegills and predation by age I+ bass are important in causing weak year classes of bass. First year growth of bass was associated with density of bass and bluegill fry available as forage. Seining is selective for smaller young-of-the-year bass, but electrofishing seems to give an unbiased sample. The 1963 year class dominated the bluegill population for two years, and it appeared that the dominance would have continued for another year. Weak year classes of bluegills were associated with strong year classes of largemouth bass: and strong year classes of bluegills, with weak year classes of bass. Bass were able to grow large enough to feed on bluegills one year older than they themselves were. It appeared that the 1965 year class of bluegills was large enough to have caused crowding in 1966.Restocking 10 largemouth bass per acre 6.0 inches and larger was not sufficient to correct crowding of small bluegills in 16 months. Angling return of the restocked fish was 43.7 per cent, and survival calculated for no fishing was 81.1 per cent. Redear sunfish reproduced in 1962 and 1963 but failed to spawn in 1964 and spawned very little in 1965. Analysis of covariance of the equation log (W) = log (a) + b log (L) suggests a seasonal cycle of condition and that a single equation should not be used for samples taken in different seasons. Stocking 100 channel catfish fingerlings per acre in a standard largemouth bass - sunfish combination is satisfactory for new ponds but the catfish do not maintain a population. Restocking large channel catfish is a questionable practice.A pond once stocked with white catfish would probably maintain a limited population without interfering with other species. Green sunfish disappear under predation by largemouth bass. Other species which entered the pond accidentally had no effect on the population.

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