Morphological and adaptational changes associated with fish migration from fresh to marine water bodies

Abstract

Expansion of the aquatic industry and increased preference on white over red meat has resulted into intensification of aquaculture practices. Inland capture fisheries in Africa are also on the increase while marine capture has stagnated over the last 20 years. This has led to unconventional fish farming where by some marine and fresh water fish species are increasingly farmed in fresh and sea waters respectively. Although some fish species can naturally survive on fresh and sea water environments, the transition between the two water bodies requires morphological changes to ensure survival and optimal productivity. Morphological changes take place concurrently, with the physiological adaptations which are critical for survival in the new environment. Artificial hatcheries can simulate environmental conditions which favour such transitions, and therefore proper understanding of the underlying anatomical and physiological changes is crucial. In this paper, we summarize and discuss available reports on the anatomical and physiological changes associated with migration of fish from fresh to sea water and vice versa. Understanding of species specific adaptational changes is crucial as farmers engage in intensive fish farming involving transfer from hypoosmotic to hyperosmotic water environments and vice versa.