Size Structure of Exploited Holothurian Natural Stocks in the Hellenic Seas

Size limitations are commonly applied as regulatory measures for the sustainable management of marine invertebrate fishery resources. However, the setting of biologically meaningful size limits in holothurians is puzzling, due to the limited knowledge of their biology and the great plasticity in size and weight, owing to the increased contractibility of their body, and the large quantity and variability of their coelomic fluid. To evaluate the efficiency of official size limits in Hellenic fishery regulation, the biometry of the exploited species, i.e., H. tubulosa, H. poli, H. mammata, and H. sanctori, was assessed in the main fishery grounds of the Hellenic Seas. Specimens of all four species were haphazardly collected and measured for total length and drained body weight at 46 sampling sites dispersed in the north Aegean, the Sporades, the Cyclades, the Dodecanese, and the Ionian fishery grounds. According to presented results, the official size limit of 180 g for drained weight appeared to be adequate for H. tubulosa and H. mammata. Adjustment of the relevant regulations for H. poli and H. sanctori are suggested by reduction to 140 g for the former and increment to 200 g for the latter species, to better fit their biological traits.