Fishery Oceanography

The ocean in itself is not a homogenous medium although it is a single phase environment. The temperature, the amount of dissolved organic and inorganic matter, the amount of dissolved gases and the physical nature of the ocean are subject to various changes seasonally and regionally. The climatic conditions of the atmosphere also affect the ocean and the exchange of energy between (he sea and the atmosphere is also important in this respect. The in situ changes in the of an affect the production of planktonic organisms which form the food material for the fish. The spatial differences in the mass distribution of the oceans which can be estimated from temperature and salinity, give rise to ocean currents, which help the transport of fish eggs and larvae and which affect the movements of adult fish also. Thus the fluctuations in the environmental conditions have a profound influence on the aperiodic and seasonal migrations and occurrence of fish. Furthermore, the conditions in the aquatic environment and their changes influence the recruitment, survival and growth of fis