Reproductive Studies on Paphia textile - Paratapes textilis - (Gmelin 1971): An Indicator of Aquaculture Management along the Egyptian waters of the Red Sea and Suez Canal

Abstract

Understanding the reproductive biology of aquatic biota is essential for better management and sustainability of coastal ecosystems and aquaculture development. The bivalve Paphia textile (Gmelin 1971) also known as Paratapes textilis, has an economic value in Indo-Pacific waters and the Red Sea. P. textile suffers from extensive fishing and exploitation. The current work aims to study the reproductive cycle of P. textile for the first time in the Egyptian waters of the Red Sea. Samples were collected monthly from two saline lakes at the Suze Gulf from December 2019 to November 2020. As part of the comprehensive research study, sex ratio, condition index, sexuality, histological analysis of the gonad maturity stages, shell size at maturity, and gonad index, were used to investigate the reproductive cycle. The results revealed that the sex ratio was male biased possibly due to anthropogenic stressors. Paphia textile has dioecious sexuality and hermaphroditism is lacking. The condition index in winter and spring indicates periods dominated by mature individuals. Five reproductive maturity stages were assigned for P. textile males and females. The prevailing warm water year-round could be the reason behind the lack of successive stages of gonad maturity and periodicity. The study indicates that gonad development is a function of temperature, salinity, and chlorophyll. The Paphia textile shell sizes at which 50% of the population reached maturity ranged between 28 mm and 34 mm for females and males, respectively. A gonad index indicates the ripe stages. Study findings suggest the most suitable temperature for aquaculture spawning is between 20 ◦C and 30 ◦C in subtropical waters, and fishing should be prohibited at sizes less than 28.60 mm in general for males and females for better management and sustainability of this aquatic resource.