Salinity Tolerance of Freshwater Shubunkin Gold Fish, Carassius auratus (Linn.): Suitability for Rearing in Inland Saline Water

Short term salinity tolerance test (10 days) was conducted to assess the stress responses in terms of fish survival, behaviour and colouration of freshwater shubunkin gold fish, Carassius auratus (L.) in different salinity levels (2 to 10 ppt). Inland saline water (15 ppt) collected from district Fazilka (Punjab) was used for preparation of different treatment salinities after dilution with freshwater (0 ppt). After proper conditioning in indoor conditions, fish were acclimatized (gradual increase in salinity @ 1 ppt at 1-hr interval) and distributed @ 10/aquaria (50 liter capacity). There was significant increase in pH and NH₃-N, however, these remained in tolerance range for freshwater fish culture. The rest of the parameters i.e. EC, TA, TH and ionic composition (Na⁺, K⁺, Ca⁺², Mg⁺², Cl⁻ and SO₄^2-) of water increased significantly in accordance with the composition of source inland saline water. At the termination of salinity tolerance test, percent fish survival did not vary significantly, however, in 0 and 2 ppt, it was 100%, which decreased to 96.66% in 4, 6 and 8 ppt and 93.33% in 10 ppt. Fish behaviour w.r.t. swimming activity and feeding responses showed gradual departure from normal behaviour. Deviation from normal skin colouration was insignificant in terms of L a*b* values and colour indices (chroma and hue) during short duration of 10 days exposure to increasing salinity conditions. Overall results are indicative of stimulation of adaptive mechanism in freshwater fish during shorter duration of salinity exposure.