Journal of the Marine Biological Association of India

Volume 37 Issue 1&2

Certain ecological impacts on the distribution and abundance of fish eggs and larvae of Vellar Estuary, Porto Novo (Bay of Bengal).

M.Thangaraja
Abstract

Distributional fluctuations of fish eggs and larvae in different zones of Vellar Estuary during lowtide and hightide, day and night and new moon and fullmoon have been studied from November 1977 to October 1979. Environmental parameters such as rainfall, atmospheric and surface water temperature and surface salinity have also been recorded. It has been observed that salinity plays a major role over the distribution of eggs in the estuary. The eggs and larvae were abundant in plankton during hightide, night and newmoon time.  A significant correlation in the distribution of eggs and larvae with season reiterates well known facts of seasonal influence on the organism. Maximum eggs and larvae was noticed during the post-monsoon (January- March) and subsequently, minimum number of eggs was recorded during the monsoon (October-December).

The influence of such factors as salinity and solar periodicity on the availability of eggs was highly significant. (P<0.01) whereas the effect of temperature was not significant. This clearly indicated that salinity of water and solar periodicity were affecting the egg availability in the estuary. Though the effect on the temperature on the egg number was not significant. There was an indication that there was a slight reduction in the number of eggs as the temperature increased. Variation in the station wise distribution of eggs was highly significant (P<0.01). Highest egg count was recorded in Station 1 and a progressive reduction of egg was noticed in all the other 3 stations. However stationwise analysis of larvae did not indicate any significant variation, in accordance with the tidal influence, the distribution of both eggs and larvae was highly significant. The abundance of eggs and larvae was very high during hightide. Hightide showed 4.9 times more eggs than lowtide and 2.1 times more larvae than lowtide. The interactions of station tide (P<0.1) and season X tide (P<0.05) on egg and larval availability and abundance were significant. Lunar periodicity was found to be highly significant on the distribution of eggs (P<0.01) and larvae (P<0.001). It was evident that the new moon has much greater influence than the fullmoon on the abundance of both eggs and larvae.

Keywords
Date : 30-12-1995