The Culture of Tilapia Nigra (Gunther) In Ponds Part Viii-The Effect of Cropping a Breeding Population by Trapping

Abstract

In Part VI of this series the effect of selective cropping of a mixed breeding population of T. nigra in three different ways was described. In those experiments cropping was carried out by monthly seine netting with a t in. mesh nylon seine, and selection was effected by hand sorting the fish in one haul. The three methods employed were: (a) removal of all large fish, returning fry alive; (b) removal of only colored males, returning all females, immature males and fry alive; and (c) removal of fry only, returning all large fish alive. The results, which were different in each case, showed a profound effect on both the periodic crop taken and the final yield on draining.