Reproductive biology of the Atlantic mackerel Scomber scombrus Linnaeus, 1758 in Mediterranean coast of Sinai, Egypt.

This work aims to investigate reproductive biology of the Atlantic mackerel (Scomber scombrus L. 1758) to provide biological base for management of its fisheries in the Mediterranean coast of Sinai, Egypt. Monthly samples of S. scombrus were collected from the commercial catch in different landing sites of the Mediterranean coast of Sinai during 2019. The length-weight relation was found as W= 0.0116 L^2.9556, W= 0.0077 L^3.091 and W= 0.0094 L^3.022715 for males, females and combined sexes respectively. Overall sex ratio (males: females) was 1: 1.4 during the period of study.  Gonado- Somatic Index (GSI) of females showed that S. scombrus spawn during March, April and May, since GSI peaked in these months (6.5, 7.2 and 5.2 % respectively). The lowest value of GSI of females was recorded in October (0.05%). Lengths at first sexual maturity (L_m) were determined as 23.2 and 23.4 cm for males and females respectively. The absolute fecundity (F) was increasing with the fish length and described by a power equation: F = 0.0014 L^5.6414. The relative fecundity gradually increased from 2481.8 to 7599.3 eggs per cm (average 4748.9 eggs / cm). To protect and maintain the stock of Atlantic mackerel in the Mediterranean coast of Sinai, it is recommended to ban using fishing nets of illegal mesh sizes and other destructive fishing methods which catch small fish sizes. Length at first capture should be larger than length at first sexual maturity (> 23.4 cm) and ban fishing nets targeting S. scombrus during its spawning season (from March to May).