Assessing the Stress Responses and Aquaculture Potential of Silver Barb (Barbonymus gonionotus) Under Saline Exposure

This study evaluated the salinity adaptation capability of silver barb (Barbonymus gonionotus) by examining its physiological and behavioral stress responses under varying saline conditions. In an acute toxicity bioassay using the direct transfer method, 180 fish were exposed to salinity levels ranging from 0 to 16 ppt for 72 hours. The species survived exposure up to 12 ppt, with a 72-hour median lethal salinity LC50 of 14 ppt determined via probit analysis. Subsequent 72-hour evaluations of body weight dynamics, gill histology, and behavior were conducted across two sub-lethal salinities (8 ppt and 12 ppt) and two lethal salinities (14 ppt and 16 ppt). Fish exposed to sub-lethal concentrations (up to 12 ppt) displayed minimal behavioral distress, a gradual decline in body weight, and minor gill alterations restricted to lamellar rupture accompanied by light mucus secretion. Conversely, exposure to lethal salinities (14 ppt and 16 ppt) induced severe physiological and behavioral stress including rapid osmotic body weight loss, marked hyper-agitation, erratic swimming, and accelerated opercular movements. Histological analysis of gills from lethally exposed fish revealed extensive structural damage, including curved and broken filaments, severe lamellar rupture, and tissue necrosis. These findings demonstrate that while elevated salinity significantly disrupts the physiology and behavior of silver barb near lethal thresholds, the species possesses sufficient tolerance to make it a promising candidate for aquaculture in low-salinity brackish environments.