Husbandry factors affecting survival and growth of carp (Cyprinus carpio L.) fry and an evaluation of dietary ingredients available in Bangladesh for the formulation of a carp fry diet

Abstract

In an effort to make a positive contribution to improving nursery management, some key husbandry and water quality requirements of common carp fry were investigated. Investigations were also conducted to evaluate some dietary ingredients available in Bangladesh for the formulation of a complete diet for carp fry.

Studies on the effect of temperature and feeding rate conducted in laboratory recirculated water systems, showed that within a temperature range of 24 to 35°C, 32°C was optimal for growth and food conversion of carp fry receiving a feeding rate of 20-30% body weight/day. It was also observed that maximum growth occurred at feeding rates of 20-25%, 25-30% and 30% BW/day at rearing temperatures of 24, 28 and 32-35®C respectively.

It is suggested, based on the experimental results, that in a recirculated water system, with a water temperature of 28°C and under fully oxygenated conditions, a stocking density of 7-11g flsh/litre can be maintained without any adverse effect on growth and food conversion provided the fish receive a feeding rate of 15-25% BW/day.

In an experimental evaluation of mustard, sesame, linseed, copra, leucaena and groundnut meals as dietary protein source for carp fry it was found that linseed followed by groundnut and sesame meal gave the most promising results. When a combination of different plant protein sources was used, linsead, groundnut and sesame meals, in various combinations up to a level representing 60% replacement of fish meal protein, proved suitable In the formulation of a complete diet for carp fry.

Experimental Investigations on the water quality requirements of carp fry showed that fish of site range 206-299 mg were fairly tolerant to un-ionised ammonia, the 96-h median lethal concentration (LC50) value ranged between 1.74 and 1.85 mgl-1 NH3-N. Nitrite tolerance of carp fry was found to be highly variable depending on the concentration of chloride and pH of water; increased tolerance was observed with Increased chloride concentration and pH of water. Nitrite tolerance, however, did not vary for carp fry weighing between 75 and 450 mg. Carp fry were found to be highly tolerant to nitrate toxicity; only concentrations of 1000 mgl¬-1 NO3-N and above proved lethal.

The temperature tolerance of carp fry at different acclimation temperatures was also investigated. The results showed that carp fry have a high incipient lethal temperature and can withstand a large fluctuation of temperature; the upper incipient lethal temperature varied between 33.5 and 38.8 °C for acclimation temperature. In the range 16 to 34°C.

The results of this study are discussed in relation to previous research publications on carp fry and to the practical problems of carp culture in Bangladesh.