Theses and Dissertations

Title: The biology of Tilapia nilotica Linnaeus

Name: McBay, Luther G.

Degree: MS

Chair: Dr. Homer S. Swingle

Resides: FAA Library

University: Auburn

Location: Auburn, Alabama

Date: 1960

Pages: 63

Keywords: Biology,Tilapia nilotica Linnaeus.


Studies concerning the reproductive behavior, spawning temperatures, fecundity, period of egg formation, food habits, and lower lethal temperature of the exotic cichlid, Tilapia nilotica, were conducted in aquaria and in the farm ponds at Auburn University. These studies suggested that the spawning behavior of T. nilotica is typical of that of many cichlids and consists of schooling, territorial establishment by the males, an intricate prespawning courtship, spawning, and parental care by the female in which the eggs are carried in the buccal cavity until hatching, and the fry remain there for about five days thereafter. T. nilotica spawned in aquaria at a constant temperature of 74 oF and spawning occurred in ponds in late April at diurnal temperatures ranging from 70 to 84 oF.The fecundity of this species was found to vary considerably with the size of the brood fish and on a seasonal basis. Relatively lighter broods were produced at the initial spawning. Mean seasonal values for 5, 6, and 7-inch fish were calculated at 160, 261, and 462 eggs, respectively. In aquaria kept in the Fisheries Building, Auburn University, spawning occurred at 6 or 7 week intervals. In the ponds, two, and possibly three spawns were produced during the period April 24, 1957, to October 12, 1957, by a single female.Egg formation in this species began at a relatively early age. Fish from ponds receiving supplemental feeding were found to form eggs when they were 4 inches in length and about 50 days old. T. nilotica was found to be omnivorous with greater concentrations of zoo-organisms, primarily Entomostraca and Chironomids, being utilized by smaller sizes of fish. T. nilotica of the 5 to 9 inch groups, in a Pithophora infested pond, utilized the algae quite extensively, whereas it comprised only a negligible part of the diet of smaller sizes of fish. Mortality due to cold water first occurred in the ponds at a temperature of 48 oF. This mortality was limited to fish less than 6 inches in length. Mortality in the larger inch groups occurred progressively with decreasing water temperatures. Some 9, 10, and 11-inch tilapias tolerated 37 oF for a short period of time: however continued exposure to temperatures below 55 oF cumulatively affected these larger fish and resulted in mortality. The last survivors of these larger inch groups were observed on January 13 after 32 days with water temperatures below 55 oF.

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