Population structure and reproductive biology of the lesser spider crab Maja crispata (Risso, 1827) (Decapoda: Brachyura: Majidae) in the Sea of Marmara, Turkey

Population structure and aspects of the reproductive biology of the widely distributed lesser spider crab, Maja crispata (Risso, 1827) (Majidae), were investigated based on 908 specimens collected monthly by scuba diving from August 2020 to July 2021 in the Sea of Marmara, Turkey. Males were predominant, with a sex ratio of 1:0.72. The mean carapace length (CL) of males (62.27 +/- 0.46 mm) was higher than that of females (56.85 +/- 0.45 mm). The largest individual (95.99 mm CL) ever recorded for the species was collected. The mean condition factor was calculated as 3.00 +/- 0.016 for males, 2.83 +/- 0.017 for females. The percentage of ovigerous females was 8.37%, which were observed between March to November. Two peaks 'July and November) of the gonadosomatic index were recorded. Length at maturity was calculated at 54.13 and 48.73 mm for males and females, respectively. Eggs were described as occurring in four main stages. Ovigerous females ranged 43.80-75.80 mm CL producing 12,167-33,939 egg individual(-1). The mean fecundity was estimated at 19,466 +/- 534 egg individual(-1), which is higher compared to those obtained in previous studies. The egg diameter ranged 170-367 mu m (Mean 275.83 mu m). The results indicate a stable population structure and long-lived adults in the Sea of Marmara.

Automated summary

This study focused on the population structure and reproductive biology of the lesser spider crab, Maja crispata, in the Sea of Marmara, Turkey. The research found a predominance of males, with the largest individual recorded for the species. Ovigerous females were observed between March to November, accounting for 8.37% of the females in the study.