Ecosystem based Adaptation Options against Salinity Intrusion in Freshwater Aquaculture System in Sundarban Delta of India

Abstract

Fish loss in freshwater ponds in Sundarban delta due to saline water intrusion during cyclones and storm surges is a serious climate induced risk for the farmers. This study tested whether problem can be solved through ecosystem based adaptation options. The study involved the assessment of eleven numbers of commonly cultured freshwater fish species for their sensitivities to salinity. In Salinity tolerance (MLS96h) test, Macrobrachium rosenbergii exhibited maximum salinity tolerance (24%o), followed by Channa punctatus (18%o), Puntiusjavanicus (17%o), Puntius sarana, Cyprinus carpio (both 13%oj, Labeo rohita fll%o), Ctenopharyngodon idella, Hypophthalmichthys molitrix, Catla catla fall 9 % o ) and Labeo bata (8%6). Growth performance study for different species at various sub-lethal salinities indicated that the freshwater fish tend to naturally adapt till a certain salinity level, but showed significant retardation in growth beyond that. The natural adaptability level was 5 % o for the species like Labeo rohita, Puntius sarana, Cyprinus carpio, Cirrhinus mrigala, Labeo bata, Ctenopharyngodon idella, Hypophthalmichthys molitrix, Catla catla; 1 0 % o for Puntius javanicus, Channa punctatus; and 1 5 % o for Macrobrachium rosenbergii. Post-flooding mortality recorded for freshwater species at different salinities (5,10,15 & 20 %o) revealed that Macrobrachium rosenbergii was the most tolerant species and could withstand sudden saline water flooding followed by Channa punctatus, Puntius javanicus, Cyprinus carpio, Puntius sarana, Labeo rohita, Cirrhinus mrigala, Ctenopharyngodon idella, Catla catla, Hypophthalmichthys molitrix, and Labeo bata. Therefore, culture of salt tolerant freshwater species can be an ecosystem based adaptation option in freshwater aquaculture for the areas vulnerable to saline water flooding.