Gonadal growth and qualitative color assessment of the sea urchin Paracentrotus lividus Lamarck, 1816 (Echinodermata: Echinoidae) of the Southeastern Mediterranean Sea

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.