الفهرس | Only 14 pages are availabe for public view |
Abstract The studies on the status of the sea urchin populations of the Red Sea are scarce. This thesis aimed to provide an overview of some aspects of sea urchins in the Northern Red Sea, Hurghada. Those marine world wide invertebrates provide myriad of opportunities for investigation. Among the Red Sea species, T. gratilla was selected to be the subject of the following investigation. It was a target species due to its high economic value in addition to the lack of studies on this species in Egypt. Sampling site was selected in front of the branch of the National Institute of Oceanography and Fisheries (NIOF). It is considered the most suitable sampling site for studying the biology of T. gratilla according to many criteria. It contains a reasonable abundance of the targeted species, suitable for snorkeling and sampling, and close to the NIOF laboratories to prepare the samples immediately after collection. Although, the collected sizes were limited to obtain more accurate estimation on growth and mortality for each size group, growth and mortality were calculated for the obtained size range. The limited sample sizes were mainly due to, the scarcity of small individuals, especially those less than 6cm total length and hiding behavior of T. gratilla under stones and in the crevices, as well as reducing the potential of collection to conserve the exited populations. This explains the dominance of large species in the sampling and might explain also the dominance of the female individuals (208 individuals, 61%) over males (131 individuals, 39%). |