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The present study was carried out to evaluate the growth pattern and population status of the sea urchin Paracentrotus lividus (Lamarck, 1816) in the Egyptian Mediterranean coast off Alexandria City. A total number of 2575 specimens were collected from their fishing grounds during 2017 to 2018. The size classes ranged from 9–57 mm with a mean value of 34.27 mm. Classes from 27 to 41 mm represented about 81.44% of the total collected catch. The length-weight relationship (Wt = 0.0039 L2.3839) reflected a pattern of negative allometric growth. Age was determined using the Bhattacharya’s method based on the length frequency data. Six age or cohort groups were recognized. The Von Bertalanffy growth equations for length and weight were found to be Lt = 71.17[1 – e-0.215(t +0.130)] and Wt = 102[1 – e-0.215(t +0.130)]2.3839. The estimated longevity tmax for the Egyptian urchin was 13.96 years. The growth indices for length and weight were Φ’L = 3.04 and Φ’Wt = 0.67. The values of total mortality (Z), natural mortality (M), and fishing mortality (F) were 1.767, 0.47, and 1.297, respectively. The Egyptian urchin population showed an exploitation ratio of 0.73, indicating an over-exploitation status. The results of the yield per recruit and the relative yield per recruit emphasized the urgent need of fishery management strategies to control the fishing practices of the edible purple sea urchin P. lividus for future sustainability of its wild population off the coast of Alexandria. Further work is also needed to investigate other P. lividus populations along the Egyptian Mediterranean coast and assess their health status.

This study aims to investigate the gonadal growth and gonads qualitative color assessment of the sea urchin Paracentrotus lividus in the Southeastern (SE) Mediterranean coast off Egypt. A total of 1895 sea urchins were collected between 2017 and 2018, and their reproductive biology parameters were determined. The gonadosomatic index with the histological analysis revealed that P. lividus has two spawning seasons (spring – autumn). Females and males have four maturity stages; recovery, growing, mature, and spent. Mature oocytes and sperms were observed during autumn, winter, and spring, while nutritive phagocytes dominated the tissue of both ovaries and testes in the summer season. The sex ratio (F: M) was male-biased (1: 1.2). The smallest observed size of mature males was 19.10 mm TD (test diameter), whereas the calculated L50 was 26.2 mm. In females, the smallest observed size of a mature individual was 22.70 mm TD, and the calculated L50 was 33.5 mm TD. The qualitative color assessment of the gonads revealed the dominance of excellent and acceptable color throughout the year (83.93%), with maximum value during the resting and recovery periods, while, the occurrence of unacceptable color was linked to the maturation and spawning periods. The present findings would assist the decision makers to propose management strategies and regulations on the harvesting of P. lividus off the Egyptian Mediterranean coast.