Growth Performance of Carps at Different Protein Ratios under Polyculture Farming: Implications for Farmers

Abstract

Aquaculture is a rather recent activity in Pakistan and is still in its infancy; nevertheless, there is immense potential for the development of the sector. Freshwater carp farming is the major aquaculture activity in four of the country's five provinces. However, the main issue fish farmers face, is the availability of cheap supplementary feed with an optimized protein ratio as the protein content in the feed has a direct effect on the fish weight gain and muscle. This study examined the effects of six isocaloric supplemental diets differing in amounts of protein (22, 24, 26, 28, 30, and 32%) on the fillet composition of rohu (Labeo rohita), catla (Catla catla), mrigal (Cirrhina mrigala), grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) raised in ponds containing natural feed. Control treatment with no supplemental feeding was also included. Mean muscle protein concentrations were significantly lower in fish from control ponds compared to ponds that received supplemental feeding, with 26% and 28% protein diets producing significantly highest muscle protein. Mean muscle lipids of 2.12% were significantly higher in muscles from fish receiving 32% protein diet compared to other treatments. Muscle ash was nearly double in fish from control ponds, where-as muscle carbohydrates were nearly double in fish from ponds receiving 22% protein diets. Among five fish species sampled, percent muscle protein was highest in rohu and lowest in silver carp, with all other species having intermediate values. Muscle lipid was greatest in grass carp and lowest in catla. Mrigal and silver carp had the greatest muscle carbohydrate, while rohu had the lowest. Supplemental feeding of diets with protein ranging from 26 to 28% is recommended during polyculture of cyprinids in ponds. Findings of the present studies ought to prove useful in the production of cost-effective and protein ratio optimized supplementary feed for the major carps and in the dissemination of high production of fish farming throughout the region.