Impact of fish stock enhancement through in-situ raising of stunted carp fingerlings in pens on fish production.

Abstract

Quality stocking material is required for fish stock enhancement in seasonally open beels to increase of fish production sustainably. To fulfill this, a pen aquaculture experiment was undertaken in a moderate sized (20 ha) seasonally open flood plain wetland of Assam (Mer beel, Nagaon district) to produce stunted carp fingerlings. Four bigsized (2500 m2 each) rectangular pens were constructed using net-lined split-bamboo screens and installed in marginal areas of the beeI during August 2015. The pens were stocked with six species of carps (Labeo rohita, Catla catla, Cirrhinus mrigala, Labeo gonius, Ctenopharyngodon idella and Hypophthalmichthys molitrix) @5 nos./m2 and reared for 5 months. Stocked fishes were initially fed with supplementary feed @3% of body weight, which was gradually reduced to 0.5% for adapting them for releasing to the beel. After 5 months of rearing, the highest specific growth rate was observed in mrigal (1.45) followed by gonius (1.14), grass carp (1.11), rohu (0.86), catla (0.86), whereas silver carp recorded the lowest SGR (0.70). The average weight of the stunted fingerlings was 150.9 g with 86% survival. Stunted carp fingerlings raised in the pens were released to the bee I proper for stock enhancement @2000 nos./ha towards partial restocking of the beel following the first major part-harvest in the beel during January, 2016. Stock enhancement was practiced intermittently in the bee I during 2007-11 and the average fish production was 507 kg/ha, which increased by 188.95% during 2016-17. During 2011-16, stock enhancement was practiced as per ICAR-CIFRI guidelines by supplementary stocking with carp fingerlings, which gave an average fish production of 1326 kg/ha with 10.48% increase during 2016-17. During 2016-17, stock enhancement was practiced by stocking stunted carp fingerling produced in pens as a stocking material, which resulted fish production of 1465 kg/ha with 12.6% increase in production compared to the previous year. The results suggest that fish production from the beels can be further enhanced by stocking stunted carp fingerlings reared in pens.