Establishment of dry-down hypoxic stress treatment protocol for snakehead freshwater fish, Channa striatus

Abstract

The air-breathing fish, Channa striatus can survive in muddy and marshy water. It is a hypoxia tolerant species. Hypoxia tolerance linked investigations for large-bodied fishes are limited in the absence of suitable laboratory-protocol. Here, a dry-down approach for hypoxia treatment in FRP (fiberglass reinforced plastics) tanks containing pond-mud and freshwater was investigated for 61 days. This facilitated lowering of dissolved oxygen (~0.15 mg/L from 39 days) in hypoxic tanks compared to ≥3.5 mg/L normoxic tanks. Hypoxia exposed fishes preferred benthic habitat with reduced locomotives and hibernated under soft-mud, whereas normoxic fishes remained active with normal air-gulping. Lactate dehydrogenase, an anaerobic glycolytic enzyme, levels were elevated in serum, liver, muscle and brain of hypoxic fishes. The heightened hsp90β gene, a stress marker, expression in hypoxic fishes was also documented. Such striking differences on the behavioral and metabolic levels were indicative of successful hypoxia stress treatment. Thus, a laboratory-based rearing protocol for investigating long-term hypoxia stress tolerance in C. striatus was established. This will also have future implications in extending this protocol in other fish species.