Length–weight relationship, condition factor, and biometric characteristics in the Mediterranean temperate sea cucumber Holothuria tubulosa (Echinodermata, Holothuroidea, Holothuriidae) from the northeastern Aegean Sea, Türkiye

The length–weight relationship (LWR), condition factor ( K ), and biometric characteristics (body wall, viscera, and gonads) of the commercially important sea cucumber, Holothuria tubulosa Gmelin, 1791, from the northeastern Aegean Sea in Türkiye were analyzed based on 327 individuals collected monthly from October 2018 to September 2019. The total length (TL), wet weight (WW), gutted weight (BW), viscera weight (VW), and gonad weight (GW) were determined for each sea cucumber to the nearest 0.1 cm for length and 0.01 g for weight. The sex of each individual was identified through macroscopic observation of gonad coloration, facilitating the categorization of biometric relationships according to sex. Results revealed negative allometric growth ( b = 1.458) for H. tubulosa , with length increasing more than weight. The allometric growth values, calculated as 1.208 in males and 1.584 in females, did not differ significantly between the sexes. The mean condition factor was 2.42 ± 1.04, displaying significant seasonal patterns, with peaks in February and October and the lowest values during summer. Notably, smaller individuals (<100 g) exhibited significantly higher K values, suggesting better health. A strong positive linear relationship was observed between wet and gutted weights ( R 2 = 0.549). Body composition analyses revealed a declining proportion of gutted weight with increasing total wet weight, whereas the relative proportions of viscera, gonads, and water content were positively correlated with body size. These findings offer region- and species-specific insights that can enhance the accuracy of stock assessments and support adaptive management strategies for the H. tubulosa fishery.