Ecological aspects of zooplankton production off Visakhapatnam (Bay of Bengal)

Abstract

The quantitative distribution of zooplankton off Visakhapatnam was investigated during the period March 1968 to February 1970. The seasonal data on the parameters like surface water temperature, salinity and oxygen were recorded. The seasonal abundance of zooplankton was estimated by volume, dry weight and numerical estimation. In general, a similarity was observed in the trend of the numbers, volume and dry weight values. Peak periods of zooplankton occurred during March-April, July-August, and November-December. In general, the major and minor peaks of abundance coincided with the south-west monsoon and north-east monsoon respectively. The major fluctuations in the numbers of total zooplankters were largely due to fluctuations in the numbers of copepods. Considering the higher turnover rate consequent on higher rate of metabolism and the occurrence of several broods in a year the standing crop of zooplankton in tropical waters may be actually more than in temperate waters. The factors which may be responsible for the variation in the quantitative abundance of the zooplankton, during the two monsoon currents, in the present area are discussed.