The Biology of Tilapia Nilotica Linneaus

Studies concerning the reproductive behavior, spawning temperatures, fecundity, period of egg formation, food habits, and lower lethal temperatures of the exotic cichlid, Tilapia nilotiea, were conducted in aquaria and in earthen ponds at Auburn University, during the period of April 1959 to June 1960. These studies suggest that the spawning behavior of T. nilotiea is typical of that of many cichlids and consists of schooling by the females, territorial establishment by the males, an intricate prespawning courtship, spawning, and parental care by the female. During this period of parental care, the eggs are carried in the buccal cavity until they hatch, and the fry remain there for about five days thereafter. T. nilotiea spawned in aquaria at a constant temperature of 740 F. Spawning occurred in ponds in late April when diurnal temperatures ranged from 70 0 to 84 ° F. The fecundity 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 7inch fish were calculated at 160, 261, and 462 eggs per spawn, respectively. In aquaria kept in the Fisheries Building, Auburn University, spawning occurred at 5 to 8 week intervals. Egg formation 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. nilotiea was omnivorous with greater concentrations of zoo-organisms, primarily Entomostraca and Chironomids, being utilized by smaller sizes of fish. T. nilotiea of the 6-and 9-inch groups, in a Pithophora infested pond, utilized the alga quite extensively, whereas it comprised only a negligible part of the diet of smaller sizes of fish. Temperature induced mortality occurred in ponds at 48° F. and was limited to fish less than 6 inches in length. Mortality in the larger inchgroups occurred progressively with decreasing water temperature. Some 9-, 10-, and ll-inch fish tolerated 37° F. for a short period of time; however continued exposure to temperatures below 55° F. 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 of water temperatures below 55° F.

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