Effect of climate change on the reproduction pattern of sea urchin Echinometra mathaei at the Gulf of Suez, Red Sea, Egypt.

The reproduction patterns of  E. mathaei's population at the Gulf of Suez  were investigated during two periods, the first was 1992-1993 and the second was 2015-2016. The effects of elevating temperature during these periods on reproduction periodicities were studied. The surface water temperature showed an increase during the period 2015-2016 by 1.36 ^oC at summer and 1.24 ^oC at winter from that recorded during 1992-1993. In 1992-1993, individuals of E. mathaei had one definite lengthy spawning season, which were expressed by main spawning period from June to August with maximum gonadal activity in July. On contrary, there was an obvious shift at the spawning season during 2015-2016; individuals of E. mathaei exhibit more than one breeding season. However, they are resting only during December, January, February, May and September. They showed four spawning seasons, the first from October to November, 2015, the second from March to April, 2016; the third from June to August, 2016, and the fourth from October to November, 2016. The overall sex ratio (males to females) during the first period (1992-1993) of the current study was 1:2.5, while in 2015-2016, it recorded an average male to female of 1:2.4. Size at sexual maturity decreased from 1992-1993 (2.25 cm for females and 2.03 cm for males) to 2015-2016 (1. 8 cm for females and 1.5 cm for males). The study recorded a positive relationship between fecundity and size. The oocyte/female was highest in 1992-1993 (23 X 10⁵), decreased during 2015-2016 (11.2 X 10⁵).  Seasonal changes were observed in maturity stages related to spawning season at both periods of study. In the first period (1992-1993),  most stages were represented with fluctuation in their percentage. The data collected showed that all stages showed one pattern of increasing and decreasing according to the stage until May, 1993 and subsequently, the pattern changed between the stages during the period from May to August. On the other hand, during the second period (2015-2016) all maturity stages were represented but in alternative states between the months of study.