Novel life-history data for threatened seahorses provide insight into fishery effects

Life-history variables for three incidentally captured species of seahorse (Kellogg's seahorse Hippocampus kelloggi, the hedgehog seahorse Hippocampus spinosissimus and the three-spot seahorse Hippocampus trimaculatus) were established using specimens obtained from 33 fisheries landing sites in Peninsular Malaysia. When samples were pooled by species across the peninsula, sex ratios were not significantly different from unity, and height and mass relationships were significant for all species. For two of these species, height at physical maturity (H-M) was smaller than the height at which reproductive activity (H-R) commenced: H. spinosissimus (H-M = 996 mm, H-R = 1232 mm) and H. trimaculatus (H-M = 905 mm, H-R = 1218 mm). For H. kelloggi, H-M could not be estimated as all individuals were physically mature, while H-R = 1674 mm. It appears that all three Hippocampus spp. were, on average, caught before reproducing; height at 50% capture (H-C) was H-M but H-R. The results from this study probe the effectiveness of assessment techniques for data-poor fisheries that rely heavily on estimates of length at maturity, especially if maturity is poorly defined. Findings also question the sustainability of H. trimaculatus catches in the south-west region of Peninsular Malaysia, where landed specimens had a notably smaller mean height (862 mm) and markedly skewed sex ratio (6% males) compared with samples from the south-east and north-west of the peninsula.