Citation: Borah, S.; Das, B.K.; Bhattacharjya, B.K.; Karnatak, G.; Yadav, A.K.; Pandit, A.; Parida, P.K.; Roy, A.; Sahoo, A.K.; Behera, B.K.; et al. Standardizing Pen Culture of Small Indigenous Fish Labeo bata in the Tropical Floodplain Wetland of the North Eastern Region, India: A Step towards Sustainable Fisheries Management. Sustainability 2023, 15, 4423. https://doi.org/10.3390/ su15054423 Academic Editor: Francesco Tiralongo Received: 29 December 2022 Revised: 18 January 2023 Accepted: 20 January 2023 Published: 1 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Standardizing Pen Culture of Small Indigenous Fish Labeo bata in the Tropical Floodplain Wetland of the North Eastern Region, India: A Step towards Sustainable Fisheries Management Simanku Borah 1, * , Basanta Kumar Das 2, *, Birendra Kumar Bhattacharjya 1 , Gunjan Karnatak 2 , Anil Kumar Yadav 1 , Arun Pandit 2 , Pranaya Kumar Parida 2 , Aparna Roy 2 , Amiya Kumar Sahoo 2 , Bijay Kumar Behera 2 , Archan Kanti Das 2 , Nilmani Rabha 1 and Priyanka Priyadarshini 1 1 ICAR—Central Inland Fisheries Research Institute Regional Centre, Guwahati 781006, India 2 ICAR—Central Inland Fisheries Research Institute, Kolkata 700120, India * Correspondence: simankuborah@gmail.com (S.B.); basantakumard@gmail.com (B.K.D.) Abstract: Labeo bata fry were reared in high-density polyethylene (HDPE) pens at different stocking densities to determine growth, survival, feed utilization efficiency and economics in Borkona beel, Barpeta, Assam. Pens (500 m 2 each) were stocked with fry at four stocking densities, 3 (SD3), 5 (SD5), 7 (SD7) and 9 (SD9) no. m −2 in triplicates. Feeding was performed twice a day at a rate of 3–5% body weight with floating pelleted feed containing 28% crude protein. Fish grew from 2.38 ± 0.30 g to 82.78 ± 3.18, 75.94 ± 0.89, 71.94 ± 0.89 and 61.81 ± 3.35 g at stocking densities of 3, 5, 7 and 9 no. m −2 , respectively. Weight gain per cent ranged from 2491.85 ± 140.56 to 3371.33 ± 133.16 and specific growth rate from 1.41 ± 0.02 to 1.55 ± 0.02, both of which decreased with increasing stocking density. The net and gross yields increased with increasing stocking density and were highest at SD9. The benefit-cost ratio was maximum at SD7 (1.42), followed by SD9 (1.41). Post-pen culture, the monthly income of fishers increased by 6.10% (SD3) to 40.50% (SD9). Significant differences (p > 0.05) in water quality parameters were not observed between treatments (inside pens) and reference site (outside pen at 10 m distance). Weight gain exhibited a significant positive correlation with temperature (r = 0.92; p = 0.029) and alkalinity (r = 0.95; p = 0.014). The present study can provide impetus towards species diversification in pen enclosures, income enhancement of small-scale wetland fishers and sustainable ecosystem-based floodplain wetland fisheries management. Keywords: floodplain wetland; Labeo bata; pen culture; small-scale fishers; sustainable management 1. Introduction Enclosure culture is a popular management choice for fish production from open water bodies [1–3]. A pen is a type of fixed enclosure, enclosed on all sides except the bottom which is the water body bed [1] and with water circulation ensured from at least one side. Pens are installed in marginal areas of open water bodies. Pollution-free sites with moderate wind action, favorable soil and water quality parameters, sufficient water depth and adequate water circulation are some of the criteria required for pen culture [4]. Pen culture is a viable option for raising quality fish seed and for table fish production [5] from open water systems of the country, particularly floodplain wetlands. Increased fish production has been realized in floodplain wetlands through supplementary stocking of pen-raised fingerlings [6]. There are reports of pen-raised fishes with a high rate of survival, a high growth rate and a high degree of disease resistance [7]. The pen culture of several species—Labeo catla, L. rohita, Cirrhinus mrigala, Hypophthalmichthys molitrix and Puntius javanicus [8], Macrobrachium rosenbergii [9], Penaeus monodon, Chanos chanos, Etroplus suratensis, Mugil sp., Lates calcarifer and Polynemus sp. [4]—have been reported from the fresh and brackish waters of India. Sustainability 2023, 15, 4423. https://doi.org/10.3390/su15054423 https://www.mdpi.com/journal/sustainability