Effect of substrate and water quality on seasonal fry production by Tilapia rendalli in tanks.

Effects of presence/absence of a spawning substrate, and of temperature and water quality changes on seasonal fry production by Tilapia rendalli broodstock, were investigated from 29 December 1989 to 19 February 1991 (416 days) in tanks at the National Aquaculture Center, Domasi, Malawi. For each of the two treatments (with vs. without substrate), four 5-m super(3) tanks were stocked with T. rendalli broodstock of similar mean size (35.8-44.2 g). Fish produced batches of sticky eggs which adhered strongly to side and bottom walls of cement tanks. Fry production was not significantly different between treatments (P>0.05, one-way ANOVA; n=81). Fry production was highly seasonal, with little or no fry production from 3 July to 25 September 1990 when minimum water temperatures dropped below 20 degree C. A multiple regression on fry production as the dependent variable was significant (P<0.05; n=136) with broodstock weight, temperature, dissolved oxygen and Secchi disk visibility (all positive regression coefficients) and substrate (negative coeficient) (as a dummy variable). Temperature was a highly significant positive predictor of fry production (P<0.01; n=136).


Costa-Pierce, B.A. (1996)
ICLARM Conf. Proc. (41): 280-289