NOPR Collection:

Distribution of ostracodes in the innershelf sediments off Kasargod, south west coast of India

Wed, 01 Sep 1999 00:00:00 GMT

Title: Distribution of ostracodes in the innershelf sediments off Kasargod, south west coast of India Authors: Reghunath, Rajesh; Murthy, T R Sreedhara; Hussain, Sk. Md. Abstract: Surface sediment samples were collected from the innershelf off Kasargod , west coast of India, to appreciate the distribution of ostracoda fauna and the controls on the same. About 21 ostracode species have been identified which belong to 17 genera. The depth wise distribution pattern reveals that the fauna is less populated up to 25 m water depth, and thereafter the population increases. Diversity index suggests open marine conditions. The ostracodes distribution pattern is related to water depth, sedimentological aspects, organic matter and carbonate distributions. Correlation analysis reveals that fine grain size, high organic matter and low carbonate content gives the minimum number of ostracodes and vice versa. Linear and multiple correlation also show that deeper depth favours the higher population. Page(s): 302-306

Intraspecific regulation in the population densities of the intertidal gastropod Planaxis sulcatus(Gastropoda, Planaxidae) in the Suez Canal

Wed, 01 Sep 1999 00:00:00 GMT

Title: Intraspecific regulation in the population densities of the intertidal gastropod Planaxis sulcatus(Gastropoda, Planaxidae) in the Suez Canal Authors: Mohammed, S Z Abstract: Monthly monitoring of the intertidal gastropod (Planaxis sulcatus) population in the Suez Canal rocky shores revealed a decrease in the adult abundance during recruitment peaks. This produced a periodical imbalance on the adult densities and reflect the regulatory roles of recruits on Planaxis population. Results of experimental manipulations to investigate these roles indicated that an increase in the overall densities reduced the rate of individual growth and declined the adult abundance. The results agreed with the hypothesis that recruits and juveniles have a competitive advantage over adults as, they are small and require less energy to survive. It is postulated, therefore that, the rapid decline in the individual numbers during intense competition could be one of the regulatory agents in the Planaxis population dynamics in the Suez Canal. Page(s): 325-328

Ferromanganese oxides on sharks' teeth from Central Indian Ocean Basin

Wed, 01 Sep 1999 00:00:00 GMT

Title: Ferromanganese oxides on sharks' teeth from Central Indian Ocean Basin Authors: Iyer, S D Abstract: The mineralogy, composition and growth rates of ferromanganese (Fe-Mn) oxides over the sharks' teeth from the Central Indian Ocean Basin are presented. The trends of metal enrichment (Mn, Ni, Cu and Zn) and depletion (Fe and Co), the Mn/Fe ratio and the growth rates, basically indicate a hydrogenous source; in contrast, limited role of diagenesis. Furthermore, the nucleus does not seem to significantly affect the nature and bulk chemistry of the Fe-Mn oxides. Page(s): 263-269

Population structure of the mullets Liza subviridis, L. carinata and Valamugil cunnesius (Family Mugilidae) from Sandspit backwaters along Karachi coast (northern Arabian Sea)

Wed, 01 Sep 1999 00:00:00 GMT

Title: Population structure of the mullets Liza subviridis, L. carinata and Valamugil cunnesius (Family Mugilidae) from Sandspit backwaters along Karachi coast (northern Arabian Sea) Authors: Samad, Mateen; Abbas, Ghulam Abstract: Among the three species, adults and some juveniles of Liza subviridis and L. carinata exhibited fair abundance and Valamugil cunnesius showed low catches. The important aspect of the study was V. cunnesius occurred only during the monsoon months (May to September). Monthly analysis of the data shows that one of the three species remained abundant in each sampling month in view of the fact that V. cunnesius formed dominating component in three hauls made in July 1992 as compared to L. subviridis and L. carinata. Such assemblage of the species collected may be due to the environmental and biological factors prevailing in the area. The stages of maturity and oocytes in the gonads indicated that spawning seems to be continuous. Spawning of L. subviridis and L. carinata starts earlier in the month of January and extends to March; while V. cunnesius spawns in July and August. Page(s): 312-319