Кормовая база тепловодных и холодноводных рыб в Черном море
The nutritive base of warm- and coldwater fishes in the Black Sea
The nutritive base of warm- and coldwater fishes in the Black Sea
Дата
1965
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Аннотация
Аннотация (alternative)
The investigation design implied studying integral nutritive base of fish not by artificial depth series but by zones naturally formed by temperature and salinity gradients in the water column of the Black Sea. The synchronous biological, hydrochemical and hydrological observations were conducted mainly in the western part of the sea during summer 1951, spring 1952, autumn 1954 and winter 1956. Assessment of the food supply in pelagic zone suggested discrimination between fodder and inedible plankton. To reliably figure out nutritive base for warm-water and for cold-water fishes, the depth of each naturally generated seawater zone, food capacity of which depends on season, should be taken into consideration. Hypothetically, warm- and cold-water fishes gather in shoals in seawater areas rich with plankton. In particular, in each of the naturally formed zones the shoals would be found within the layers of greater plankton concentration which, except for winter, form closely to the zone boundaries: either above thermocline and halocline or near the sea bed in daytime, or under the surface and below thermocline in dark time. In winter when upper seawater layers change to a seasonally hostile habitat, both plankton groups go down deeper to have concentrated near the sea bottom and in the centre of convection zone.