TOLERÂNCIA AGUDA E CRÔNICA À SALINIDADE DE JUVENIS DE PANGASIUS (Pangasianodon hypophthalmus).

It is believed that the commercial production of pangasius is viable in ponds or tanks supplied with saline water, as an alternative for the semi-arid region in Brazil, known for its scarcity of drinking water. In this sense, the objective of this experiment was to evaluate the acute and chronic tolerance of juvenile pangasius submitted to different salinities. 216 juveniles pangasius (17.30 ± 5.26 g) were distributed in a completely randomized design, with four treatments and four replicates. For the acute toxicity test, four salinities (5; 10; 12.5, and 15‰) and a control treatment (fresh water - 0‰) were tested. Based on the results obtained in the acute toxicity test, saline concentrations for the chronic tolerance test were determined: 5; 7.5 and 10‰ and control (0‰). In this trial, fish growth parameters (weight, length, weight gain, feed intake, and mortality rate) and water physicochemical parameters (temperature, pH, and toxic ammonia) were evaluated. Additionally, visual observations were made in order to observe morphological or behavioral changes due to exposure to different salinities. Mean lethal salinity (SL50) for pangasius under the study conditions was estimated at 10.76‰ (95% CI = 10.22-11.33‰). Higher weight gain rates (p <0.05) were observed between 5 and 7.5‰ salinity ranges. No differences (p≥0.05) were observed among average weight, final length and physicochemical parameters of water at the salt concentrations studied. Morphological and behavioral changes were detected in fish from control treatment and salinities 7.5 and 10‰. Results suggest that pangasius presents a relative tolerance to salinity. However, it is necessary to deepen field studies on the real influence of salinity on this species, aiming at evaluating the possible effects on growth throughout productive cycle, so that it is possible to determine the real potential of cultivation under these conditions. [ABSTRACT FROM AUTHOR]