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Copyright of Egyptian Journal of Aquatic Biology & Fisheries is the property of Egyptian Society for Fisheries Development & Human Health and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study focused on understanding the reproductive biology of Pinctada margaritifera, commonly known as the black-lipped pearl oyster, which holds significant economic importance due to its production of Tahitian cultured pearls. Research conducted in Mabahiss Bay, the Red Sea, Egypt throughout 2022 provided crucial insights into the reproductive cycle of P. margaritifera. The species exhibits protandric hermaphroditism, transitioning from male to female during its growth. Shell sizes inversely correlated with sex distribution, with a sex ratio of 1.05: 1.0: 0.1 for females, males, and undifferentiated individuals, respectively. The study identified a distinct spawning phase from June to October, peaking in July and August. Analyses of gonad index fluctuations in females and males provided additional understanding of reproductive dynamics. Among the methods tested to stimulate spawning, hormones and gonad stripping yielded positive results. The research also delved into the timing and early development stages of eggs and larvae of P. margaritifera. [ABSTRACT FROM AUTHOR]

The occurrence of some carcinogenic metals; Cu, Ni, Pb and Cd was investigated in sediment samples collected from 12 stations at Great Bitter and Timsah lakes. In the same time, two of the most famous edible bivalve species (Ruditapes decussatus and Paratapes undulatus) live buried in these sediments were chosen for measuring the same metals within their edible tissues in order to investigate the permissibility limits for human consumption. The bio-available forms of these metals were measured in the bulk sediments and the finest fractions (Ø3, Ø4 and Ø5) and in the edible tissues (flesh) of the selected bivalve individuals using a flame atomic absorption spectrophotometer (AAS). The finest fraction (Ø5) recorded the highest averages of most carcinogenic metals at Great Bitter and Timsah lakes with significant occurrences of Cd at both lakes. Carcinogenic Cd in the edible tissues of P. undulates and R. decussatus showed neglected low contents at the Great Bitter and Timsah lakes in spite of its very high contents in the surrounding sediment layer. Ni, Cu, and Pb averages in the edible tissues of P. undulates at the Great Bitter lake were 1.32, 0.23 and 0.37 μg/g wet wt. respectively. The averages of Ni, Cu and Pb in R. decussatus at Timsah Lake, were; 1.30, 0.24 and 0.95 μg/g wet wt. and in P. undulates were; 0.79, 0.14, and 1.15 μg/g wet wt. respectively. Bio-sediment accumulation factor (BSAF) in the different bivalve species at the Great Bitter and Timsah lakes were much lower than unity (<<<1.0) indicating that the bivalves tend to accumulate their needs only from the surrounding environment. Finally, the investigated metals in the edible tissues of the different bivalve species are within the permissible safe limits for human consumption except for Pb that exceeds these limits and showed a slight hazard to health risk. [ABSTRACT FROM AUTHOR]

Using photo-identification techniques, 30 dugongs were recorded at the southern Egyptian Red Sea coast between December 2015 and October 2017, 16 at Marsa Alam and 14 at Wadi El Gemal National Park (WGNP). Males were recorded seven times more frequently than females and calves were also recorded. A Photo ID catalogue was prepared for the dugongs with records of their occurrence among sites. We confirmed the presence of particular dugong specific sites. Long- and short-distance movements within the study sites were recorded for eight different dugongs. This is the first study to document the number of dugongs in inshore areas of the Egyptian Red Sea coast. Further studies are recommended for offshore sites in WGNP for better documentation of this group of animals. [ABSTRACT FROM AUTHOR]