Production performance of Indian major carps(Labeo rohita, Gibelion catla and Cirrhinus cirrhosus) fingerlings in overwintering ponds

Abstract

The production performance of Indian major carp (IMC) fingerlings of Rui (Labeo rohita), Catla (Gibelion catla), and Mrigal (Cirrhinus cirrhosus) in overwintering ponds is of great importance in the aquaculture of Bangladesh. The present study was conducted in several overwintering practiced districts from July 2019 to December 2022 to investigate the production performances of IMC fingerlings in overwintering nursing ponds, Current culture practices, challenges, and aspects of potential improvements in overwintering techniques in Bangladesh. The findings of this study revealed that the current practices of IMC overwintering varied with districts. It was observed that the demand for overwintered IMC fry was higher in the Rajshahi district, indicating a promising market potential for the region. Additionally, Khulna district showed higher production and profitability, with farmers earning over TK 2 lac/acre through the sale of overwintered IMCs. However, various constraints such as lack of technical knowledge, limited availability of good-sourced IMCs, inadequate supply of quality fry, high feed prices, and disease outbreaks were identified as major challenges for overwintering nursing production. Addressing these challenges necessitates investment in training and capacity building for hatchery and nursery operators, thereby can help in improving the overall growth and efficiency of the aquaculture industry in Bangladesh. This study also investigated the limnology and biology of fish in overwintered ponds for better understanding of the feeding behavior of IMC fingerlings under the influence of environmental factors. Water quality parameters and sediment constitution were found to be suitable for fish culture in the studied ponds. Feeding behavior varied among the IMC fingerling species. L. rohita primarily feeds on plant matter in the water column, G. catla feeds on zooplankton at the water surface, and C. cirrhosus feeds from the pond bottom. Seasonal variations in food consumption by IMCs were observed where higher consumption rates were found during post-winter which reduced rates of food intake during the winter season. The study suggested that additional feeding during winter is unnecessary as IMCs reduce their food intake during cold weather, emphasizing the importance of minimizing stress and ensuring proper care in the nursing ponds. Microbial ecology and diversity in overwintered IMC ponds were examined. Various microbial genera, including Vibrio sp., Aeromonas sp., Enterobacter sp., Klebsiella sp., Proteus sp., Exiguobacterium sp., and Escherichia coli were recorded from the ponds. The prevalence of E. coli and Vibrio species was higher in nursing ponds during the rainy and summer seasons. Antibiogram resistance profiles of isolated bacteria indicated some degree of resistance to certain antibiotics, highlighting the need to understand bacterial infections in the context of IMC aquaculture. This knowledge can contribute to the effective approaches for disease prevention and management in overwintered ponds, thus promoting the sustainability of IMC practices. The study further explored the hematological parameters, proximate composition, and growth of IMCs during winter and summer seasons. Red blood cell count and hemoglobin were observed to be stable in L. rohita and G. catla, while white blood cell iii count decreased during winter. Adaptations to reduced oxygen availability were noted in G. catla and C. cirrhosus, as indicated by decreased hematocrit values. Significant variations in other hematological parameters and glucose levels suggested unstable physiological states and potential changes in renal activity during the winter season. Proximate composition of overwintered fishes revealed that the moisture, carbohydrate, protein, ash, and lipid content varied with season. The growth performance varied during different seasons while the water quality was suitable for nursing. Stunted growth was observed in winter, while all IMC species showed proliferated growth in the summer season. This finding concludes that stocking of overwintered multispecies fingerlings in nursing ponds can lead to higher yields in a shorter rearing period, thereby reducing the operational costs for farmers. Further, policymakers, extension workers, and practitioners can utilize these insights to enhance the profitability, and sustainability of IMC culture, for boosting production by benefiting the future demand lead carp aquaculture industry.