NAGAPATTINAM: The Krishi Vigyan Kendra here has commenced a study on the feasibility of culturing periphytons in fish farm ponds in the district to enhance carp production. Based on the success of the study, the technology will be recommended to more inland fish farmers, institute experts said.
Periphyton is a complex mixture of algae, bacteria, other microbes and dead organic matter attached to submerged surfaces in aquatic ecosystems. They can absorb contaminants and help maintain water quality. It also serves as an important food source for some fishes.
As part of their study, KVK stocked on around a thousand fingerlings of rohu (Labeo rohita) in a combined area of an acre spread over two farm ponds in Themangalam and Ottathattai villages. The average length and weight of a fingerling were recorded as 8 cm and 6.5 g respectively.
Two farmers S Iyappan of Themangalam and R Santhanamary of Ottathattai were recently trained on freshwater carp farming in a programme conducted by KVK and sponsored by NABARD. The two farmers have been advised to feed the fingerlings floating pellet feed which contains 32% crude protein. They have been advised to feed at the rate of 7% biomass of the fingerlings.
Santhanamary said, "I am hoping that promoting such a mixture of microorganisms will provide my carps with a natural food source and nutrition, and increase their yield over time." Further, KVK staff planted bamboo poles in the ponds and tied fishing nets between them. They stated that the bamboo pole and the nets act as an artificial substratum for periphytonic growth.
The periphytic community will consume the excess nutrients available in the pond for their growth and, in turn, act as natural feed for herbivorous fishes like carp, they added. KVK's fisheries expert E Hino Fernando said, "The regular carp culture technology depends mainly on naturally available plankton (both phytoplankton and zooplankton) and supplementary feeding such as rice bran and groundnut oil cake. In this technology, the fish culture is dependent on periphyton growing on artificial substrates.
Promoting periphytic growth is a method of in-situ food production. Such methods will aid sustainable yield enhancement for carps." The experts added that the assemblage of both autotrophic and heterotrophic microorganisms, and algae grown on the substrate, would serve as a water conditioner and ensure a healthy environment for the fish to grow.
The institute is planning to sample the fish, observe their growth and record the data periodically. Based on the results, KVK is planning to disseminate the technology to other inland fish farmers across the district.