Aggregation of Euphausia sibogae during summer monsoon along the southwest coast of India

Abstract

The influence of environmental parameters on the spawning aggregation of Euphausia sibogae was investigated along the southwest coast of India during the peak phase of summer monsoon 2005. The prevailing ecological conditions between the aggregation period (peak phase) and non-aggregation period (early phase) were also compared. The aggregation was observed at station 1 (8 degrees N; 76.5 degrees E, 480 ind.m sup(−3)) and 6 (10 degrees N; 75.5 degrees E, 839 ind.m sup(−3)) during the peak phase of the summer monsoon. Eggs (14769 eggs m sup(−3)) and different developmental stages were observed in higher abundance at station 6. The physicochemical conditions indicated that the aggregation coincided with the upwelling. The nutrient enrichment due to the upwelling triggered phytoplankton blooms, and this appeared to provide a conducive environment for spawning and development of E. sibogae.