Dietary calcium requirement in fishes

The dietary requirement of calcium ( C a) has been well established in terrestrial animals. However, investigations for dietary C a requirement in fish are complicated and reports limited as fish can use waterborne C a in addition to dietary C a. Ca absorption in fishes from environmental water is species specific and depends on concentration of C a in rearing environment and availability of dietary C a. Ca and phosphorus are generally combined together in fish body therefore maintaining a dietary calcium: phosphorus ratio is important. Ca exists in a complex form in fish meal, which is not available to fishes; hence, although fish meal contains an appreciable amount of calcium, dietary C a supplementation in fish meal‐based diets for some species is necessary. This review article summarizes and discusses pertinent information on absorption of C a from water, essentiality of dietary C a, bioavailability of C a from different sources, optimum calcium:phosphorus ratio and dietary C a requirement in fishes.