Aspects on respiratory physiology of cultured Sea bream, Sparidentex hasta (Valenciennes 1830), Kingdom of Bahrain

Abstract

Cultured fish Sea bream, Sparidentex hasta collected from the National Mariculture Center (NaMaC) at Ras Hayan in the Kingdom of Bahrain, were subjected to extreme low dissolved oxygen concentrations under controlled experimental conditions for 24 h and continued up to three consecutive days. The metabolic rate as represented by oxygen consumption rate (mg/l/g/h), was measured using intermittent computerised respirometry system. The fish responded in general, by irregular and low metabolism. Elevated ventilation in gills was observed in order to intake more oxygen from surrounding water. An increase in oxygen consumption rate was recorded at different stress levels including initial handling and movements as well as at the onset of hypoxia. Similar findings were obtained for the level at which fish mortality attained 100% representing lethal points. The fish regulatory ability to withstand declining oxygen concentration in the water was limited. A typical steep straight line relationship was found between oxygen consumption rate and oxygen concentration indicating a non regulatory ability and extreme in-tolerance to hypoxia. Therefore, the fish is considered as oxy-conformer, i.e., unable to continue metabolism at anaerobic condition. Correlation between minimum (basic) oxygen consumption rate and body weight was of non-linear form. The present study provides comparative data to base on for further prospective related studies on juvenile Sea bream and other fish species.