High temperature tolerance limits and changes of hemato-biochemical parameters of mrigal, Cirrhinus mrigala

Abstract

The change in water temperature due to anthropogenic and climatic changes is expected to affect the physiology of fish. In this study, we determined high temperature tolerance (CTmax) and oxygen consumption rate of Indian major carp, Mrigal, Cirrhinus mrigala fingerlings followed by the acclimatization at three temperature regimes (31, 34, 37 oC). During the determination of CTmax, we analyzed the major hemato-biochemical indices - hemoglobin (Hb), red blood cell (RBC), white blood cell (WBC), and blood glucose levels in the sampled fish at the starting point and end point of the acclimated temperatures. Significantly decreased CTmax of the fish was found at 37 oC compared to 31 oC and 34 oC. Conversely, oxygen consumption rate of the fish significantly increased at 37 oC compared to 31 oC and 34 oC. The Hb levels and RBC content of the fish showed a significant decrease at the end point of thermal tolerance in each temperature group and even with the increase of acclimation temperature. On the other hand, WBC and blood glucose levels exhibited opposite scenario. Hematological and biochemical parameters have been acknowledged as valuable tools for monitoring fish health and monitoring any changes in the quality of water. The hematological studies on fishes have assumed greater significance due to the increasing emphasis on aquaculture. This research provides the knowledge of the characteristics of hematological parameters of freshwater fishes.