Theses and Dissertations

Title: A reproduction control factor in fishes

Name: Greene, George Nystrom

Degree: PhD

Chair: Dr. E.W. Shell

Resides: FAA Library

University: Auburn

Location: Auburn, Alabama

Date: 1964

Pages: 71

Keywords: Reproduction,Control Factor.


This investigation was begun to study interspecific and intraspecific repression of reproduction of fishes, the physical and chemical nature of the repressive factor, and the population densities and lengths of time required to produce a repressive factor under various conditions. Water conditioned by zebrafish, Brachydanio rerio, goldfish, Carassius auratus, carp, Cyprinus carpio, and redear sunfish, Lepomis microlophus, was tested to determine whether it would repress reproduction of zebrafish in aquaria. Water conditioned by goldfish was tested to determine if it would repress reproduction of goldfish in small ponds. Chemical analyses were performed on samples of conditioned water from the various sources to relate the repressive effect to the chemical composition. An unrelated species of fish (redear sunfish) did not produce a factor repressing reproduction of zebrafish, but related species (goldfish and carp) produced a factor which repressed reproduction of zebrafish. Zebrafish produced a factor which repressed their own spawning when held for 60 days or more at a stocking rate of at least 26.9 grams in 40 liters of water. Under the conditions of these experiments no repression of reproduction related to the length of time or stocking rate of goldfish in aquaria was demonstrated. A high ammonia content (20 to 25 parts per million) in water conditioned by goldfish in aquaria was found to be a factor which repressed reproduction of zebrafish. A factor which repressed reproduction of zebrafish was extracted with chloroform from water conditioned by goldfish in aquaria. Ether did not extract the repressive factor. In ponds, oxygen levels below 3.4 parts per million during the dawn spawning time acted to repress spawning by goldfish. Neither fingerlings, fry, nor eggs of goldfish were effective in repressing reproduction of adult goldfish. A social factor, acting in conjunction with a chemical factor, may have repressed reproduction in goldfish.

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