Evaluation of Optimal Species Ratio to Maximize Fish Polyculture Production

Abstract

There are questions remaining about many aspects relating to fish food, including, the type of organisms consumed, mechanisms of consumption, and the digestibility and nutritive value of plankton. Common practice has been to divide fish into different types according to foraging in natural habitats, that is, fish are described as feeding on phytoplankton, zooplankton, benthic animals, macrophytes, or detritus. The distinction between the different feeding habits is not always absolute. Although species such as rohu, Labeo rohita, mrigal, Cirrhinus mrigala(Indian major carp), and Nile tilapia, Oreochromis niloticus(African origin) are omnivorous, their adaptability in different climatic conditions varies. A study was carried out to determine the optimal stocking ratio of tilapia and Indian major carp (rohu and mrigal) and with common carp, Cyprinus carpio; silver carp, Hypophthalmichthys molitrix; and big head carp, Aristichthys nobilisin polyculture. Four ratios of Nile tilapia and Indian and Chinese carp (60%, 40%, 20% and 0%) were tested in pig and in cow manure fertilized ponds. Results of this study indicated that the fish ratio and manure type significantly influenced fish survival and biomass over time. The interaction between species ratio, pH, and alkalinity was found to be significant. The stocking density of rohu, mrigal, and tilapia influenced fish survival and biomass production. Ratio 1 with 60% Nile tilapia was the poorest performing treatment in both types of manure. Ratio 3 (20% Nile tilapia, 20% silver carp, 10% big head, 20% rohu and 20% mrigal) was the best performing ratio in pig treatments. Fish production in ratio 2 and ratio 4 with cow manure treatments were not significantly different. In general, fish production in pig manure fertilized ponds was significantly higher than in cow manure treatments.

Key Words:

• Carp polyculture
• organic fertilization
• species ratio
• Nile tilapia