World Aquaculture Magazine - September 2021

68 SEP TEMBER 2021 • WORLD AQUACULTURE • WWW.WA S .ORG mainstay of culture-based fisheries. Floating water hyacinth was totally removed while emergent plants such Phragmitis kerka and Nelumbo nucifera, Nymphoides indica growing in marginal areas was removed in patches to facilitate net deployment and fishing operations. Rooted emergent macrophytes in Majharia and Rulhi maun and floating macrophytes in Kararia maun were removed by physical means for improving the habitat. Approximately 20- 30 percent of the macrophytes (submerged and emergent) were retained to maintain ecological integrity. Net Pens for Production ofAdvancedFingerlings andTableFish Pre-fabricated CIFRI HDPE net pens were installed in marginal areas of wetlands as nurseries for raising fish seed for stocking. Each wetland was provided with a 0.8-ha HDPE pen. Pens were stocked with the Indian major carps catla Catla catla , and rohu Labeo rohita , common carp, Cyprinus carpio and grass carp, Ctenopharyngodon idella . Very encouraging growth of seed was observed in pens and advanced fingerlings (>100 mm) were produced in 35-40 days. Fishers actively participated in pen-culture activity and understood the advantages of the new pen material and its ease of installation. In the years that followed, the fishers formed groups, installed the same net pens and started producing the advanced fingerlings themselves. Fishers found this technology as a very handy tool for producing fish seed at any suitable place and time in the wetland owing to its easy installation, removal, storage and operation. Batteries of CIFRI galvanized iron (GI) cages were installed in selected wetlands at suitable sites where water depth was more than 5 m. Six cages were installed in both Rulhi and Majharia mauns and 12 cages were installed in Sirsa maun . Cage dimensions were modified to suit the shallow depth of the wetland. Cages ensured availability of advanced fingerlings during the post-flood season (September-October) as stocking material. Cages were successfully used for raising seed of Indian major carps and table fish production of catla, rohu, singhi (stinging catfish) Heteropneustes fossilis and pangas Pangasianodon hypophthalmus in three wetlands. Table fish production in cages provided compensatory income to fishers during closed fishing seasons. NurseryPonds for Production ofAdvancedFingerlings Nursery ponds are considered to be an integral part of culture- based fisheries in oxbow lakes, where seed stocking is a mainstay of fisheries enhancement. Provision of nursery ponds in the vicinity of lakes ensured timely availability of cost-effective quality seed of desired size. Seed produced in these nurseries proved to be better in terms of growth and survival. Nursery ponds were excavated for production of advanced fingerlings to meet seed requirement of respective wetlands. Nursery ponds were constructed near Majharia (3), Ruhi (6) and Kararia (4). Ponds were also utilized for the culture of the highly prized native fish singhi during the fallow period, providing additional income to fishers. The infrastructure created will also contribute to fisher’s income through sale of surplus seed, in addition to meeting their own requirement. Nursery ponds in each wetland were provided with a bore well as a primary water source but were also equipped with a submersible pump to ensure availability of water during the summer season and for water management in nurseries. Biosecurity fencing was provided on the banks of nursery ponds to prevent entry of predatory fishes and other animals and escape of fish stock during flooding. Management inputs, such as cowdung compost, feed, lime and prophylactic chemicals were also provided. Installation of EscapeBarriers The wetlands in Bihar are prone to flooding during the monsoon season, causing escape of stocked fishes. Fish escape channels were identified and fitted with iron mesh screens attached to concrete columns to prevent loss of stocked fishes. The barriers also prevented entry of large predators that would normally enter with flood waters from rivers. However, to maintain natural biodiversity of the wetland ecosystem, access to the oxbow lakes by eggs, fry and juveniles of riverine species was not prevented. Training, CapacityBuilding andExposureVisits The lessees and fishers engaged in fisheries of these wetlands lacked understanding of the principles of fisheries management. They lacked the knowledge behind staggered stocking and the rationale for the stocking schedule. The importance of group formation, cooperation, compliance of better management practices, observance of closed seasons, mesh-size regulation, catch quotas and regulation of destructive fishing practices were almost unknown to them. The impact of stocking interventions on fish yield in four oxbow lakes. The increase in fishing days due to technological interventions.