THE EFFECT OF PHOTOPERIOD ON THE GROWTH AND SURVIVAL OF AFRICAN MUDFISH Heterobranchus bidorsalis

Abstract

The effect of three photoperiods on growth and survival of African mudfish, Heterobranchus bidorsalis juveniles
was investigated for a period of 56 days. Forty five juveniles of initial average weight of 35g were exposed to total
darkness, partial darkness and full light throughout the study period in a partial flow-through system under
laboratory conditions. The juveniles were stocked in triplicate treatment and fed 45% crude protein prepared diet
daily at 5% body weight. Juveniles reared in total darkness exhibited significant (P<0.01) higher feed intake,
weight gain, specific growth rate, protein efficiency ratio, and lowest percentage mortality than those cultured in
partial darkness. Similarly, same parameters were significantly (P<0.01) higher in juveniles reared in partial light
than those in full light. Also, the juveniles cultured in total darkness had significantly (P<0.01) lowest uneaten feed
and feed conversion ratio, than those reared in partial darkness and full light. Fish cultured in total darkness had
darker skin colorations than those in full light. It was concluded that rearing Heterobranchus bidorsalis in totally
dark culture chamber could result in reduced wastage of feed, improved growth rate and enhanced profit especially
in the developing countries where fish production presents strong potential in alleviating food crisis.