Some ecological aspects and potential threats to an intertidal gastropod, Umbonium vestiarium.

Kalbadevi Bay in Ratgnairi has been identified as potential site for placer mining along the west coast of India. Since, U. vestiarium is a keystone species of the region; study on some ecological aspect was carried. The paper also discusses the possible impact of beach sand mining and other threats to this ecologically important gastropod. Seasonal sampling was carried in 2004-2005 at 13 transects by quadrate method. U. vestiarium was restricted to mid and low tide zone of Station 1-3 and 8-10 located at the north and south ends of the beach. Abundance was highest at Station 10 MT (16 to 12488 ind m-2). Based on the size-frequency, it may be considered that U. vestiarium like other tropical fauna recruit during monsoon. Eleven different colour patterns of U. vestiarium were observed. However, average individual size was larger in the samples collected from the north (stn. 1-3) end of the beach. The fastidious nature and sporadic distribution of U. vestiarium make them vulnerable to natural and anthropogenic disturbance.

Zooplankton biomass and abundance of Antarctic krill Euphausia superba DANA in Indian ocean sector of the southern ocean.

Zooplankton sampling was carried out during the first six Indian Scientific Expeditions to Antarctica (1981—1987) to estimate krill abundance in the Indian sector of the southern ocean (between 35° to 70° S and 10° to 52° E). This study aims to understand the distribution of biomass of zooplankton, especially the krill, using the data collected by net sampling techniques. Total zooplankton biomass for all the sampling stations ranged from 9 to 684 ml/1000m3 (x : 143·34±138·61 SD; n=150). Biomass data grouped by 5° latitude interval shows the presence of higher biomass (x: 191 ml/1000 m3; n = 31) in the Antarctic divergence region (between 60° to 65° S). Euphausiid Euphausia superba DANA formed a considerable component of biomass and together with eggs and larvae represented over 60% (n = 39) of mean total zooplankton-biomass in the coastal ice region. The values for population density and biomass of adult-size krill varied between 0 to 4320 individuals and 6 to 305 ml/1000 m3, respectively. The highest values were recorded between 62° to 69° S and between 16° to 30° E. A high density of krill larvae was encountered in the shelf region during January 1987 which was related to chlorophyll concentration. However, the values obtained during six consecutive summers showed that values of adult krill biomass at given location was highly variable and, hence, not comparable on inter-annual basis, during the sampling years.