Seasonal availability and population structure of Eurobowmaniella simulans W. Tattersall, 1915 (Crustacea: Mysida) along Vizhinjam coast, Kerala, India

Abstract

Eurobowmaniella simulans is the commonly available species of mysid along the Vizhinjam coast of Kerala. Sampling of mysids has been carried out over a period of one year from March 2014 to February 2015 to study the seasonal availability and population structure. Monthly samples of mysids consisted of individuals in various developmental stages, from juveniles to mature mysids around the year, but their percentage availability varied. The peak availability of mysids was recorded during September (2014) (avg. 48,731 numbers per haul) and their availability was lowest in July (2014) with an average of 2 individuals per haul. The availability of brooding or ovigerous females were observed throughout the year and highest and lowest percentage availability was during November (2014) and April (2014) respectively. Morphometric measurements of E. simulans revealed that their average size (TL) ranged from 2.35±0.52 mm- (juvenile) to 7.47±1.75 mm (adult). Sex could be first distinguished externally when mysid attains the total length between 4.1 mm and 5 mm. Analysis of variance of different water quality parameters and mysid density comparing seasons revealed that there was significant variation of mysid availability between seasons (P < 0.05). Multivariate Pearson’s correlation analysis of water quality parameters and mysid density showed that there was a significant relation with chlorophyll a content (P < 0.001) of seawater. The present study also revealed that mysids are available in harvestable quantities for aquaculture purposes from August to November.