1Life history and Population Dynamics of an Estuarine Amphipod –Eriopisa chilkensis

The life cycle of the gammarid amphipod Eriopisa chilkensis Chilton from the Cochin estuary, south west coast of India was studied for the first time under laboratory conditions. Amphipods especially gammarids are known as potential live feed in fish culture and this forms the base of our study. E. chilkensis can withstand wide variations in salinity (5-35) and temperature (27.5-34 °C) of the medium. It was cultured in unaerated finger bowls using dried algal matter (Chara sp.) as food. Life span of females was found to be higher (maximum: 220 days) than males (maximum: 175 days). Females were iteroparous and attained sexual maturity within 39.3 ± 6 days (mean ± SD), whereas males matured within 26.5 ± 5.6 days. Number of broods in a life span ranged from 4 to 7. The maximum number of juveniles produced in a single brood was 29 and the maximum number of juveniles produced by a single female over a lifetime was 139. The duration of embryonic development was 12 ± 2.45 days. Population dynamics of E. chilkensis was studied based on monthly sampling over one year from the mangrove swamps of Puduvypin. It occurred in varying densities in the epifaunal community (21-1583 ind. m-). Extrapolation of laboratory data to the field suggests that E. chilkensis in Cochin estuary has a multivoltine life cycle