IND UCTION OF SPAW NING IN THE TR OPICAL WALKING CATFISH (C la rias b atr ac hus) BY CONTROLLI NG WATER L EVEL AND T EMPERAT URE

This experiment was carried out t o confirm the rol e of water level and w ater temperature i n indu cing t he s pawning o f tr opical walking catfi sh . Ma ture mal es an d females reared un de r 23 - 2 5 °C, were paired and in duced to spa wn by cont rolling w ater level and w ater temperature. Decr easi ng water level and returni ng it to its original level r esulted i n a low spawni ng r ate (l es s t han 6. 7 %) at 23 °C . Decreasing water level with simultaneous increase in water temperature, followed by returning the respective levels to their originals gave high spa wning rates ( 41.7 — 50 %); whereas the s ame treatment but without a ny water temperature decrea sed when t he wate r le vel was return ed t o t he initial level, gave a lo w spawning rate (16 .7 %). In creasin g water level only, fail ed to ind uce spa wning . A high spawning rate was obtained also when changes in water level were ca rried out under high t emperature of 28 °C. No fish spawned in the ab sence of the environmental stimulation. From the results, i t is confirmed that water le vel and t emperature play important r oles i n i nducin g spaw ning of tropical walki ng catfish. Changes i n water t emperature probably increas e the sensitivity of fish to th e change in water level. Prolo nged exposure to high water tem perature c ould also improve the sensitivity of fish.