Laboratory experiments on the growth of tilapia spp.

Summary

• (1) Experiments on controlled populations of T. zillii fry kept under certain constant environmental conditions indicate that strong periodic illumination for 12 hour periods appears to delay sexual maturity, and that various intensities of light do not appear to affect the growth rate when temperature and feeding are held constant, up to a period of eight months.

• (2) On the other hand, under periodic low illumination, the growth rate is markedly affected by temperature, being greater at higher temperatures up to 31.0° C, than at lower temperatures down to 19.8° C.

• (3) Sexual maturity is also attained earlier at higher temperatures, lower temperatures retarding the onset of maturation.

• (4) Mortality of fish under these conditions appears to be greater under strong light intensities than in dark conditions, and greater in cold conditions down to 19.8° C than at higher temperatures.