ABSTRACT
Temperate seas are those that lie between tropical and polar waters. Seasonality is typically marked both in terms of temperature and photoperiod variations, which entrain a wide spectrum of physical and biological changes throughout the annual cycle. On the contrary, tropical seas are much less affected by these kind of seasonal variations, although seasonality is often expressed by other factors such as changes in current directions and intensity, frequency of storms, changes in salinity in coastal waters and many other parameters, so that the old idea of the tropics as devoid of seasonality is no longer accepted (Russell et al., 1977; LoweMcConnell, 1979; Munro et al., 1990; Conover, 1992). In polar waters, seasonality reaches extremes of severity, with freezing temperatures and ice cover being prominent features in the winter. Temperate waters have
an intermediate situation both in latitude and physical, chemical and biological conditions between the warm tropics and the extreme polar environments. These conditions allow the co-occurrence in temperate regions of tropical and subtropical fishes that manage to survive and often breed there, along with fishes that are more abundant in boreal environments.
