Life-history reference points for management of an exploited tropical seahorse

Abstract

The present research provides the first demographic reference points for tropical seahorses, relevant to conservation of this largely tropical genus Hippocampus, which is listed on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II. Findings defined the life-history and in situ vital rates of the tiger tail seahorse, H. comes, expanding previous understanding of demographic diversity in reef fishes. We quantified growth, reproduction and survival rates, drawing on mark–recapture intervals from focal observations, underwater visual census and fisheries landings data. The smallest settled individual was 2.7 cm and first benthic cohorts measured 3.0–4.0 cm. Assuming individually variable growth, the mean parameters for the von Bertalanffy growth equation were Linf = 16.7 cm, K = 2.9 year–1 and t0 = 0.03. Physical maturity occurred at 9.3 cm, reproductive activity at 11.6 cm and annual recruitment during the dry, inter-monsoon window from February to May. Size-dependent survivorship ranged from 3.5% to 45.0% year–1 and longevity was ≥2.5 years. In H. comes, characteristics governing population turnover align with opportunistic strategists, whereas reproductive traits align more closely with equilibrium strategists. Non-extractive marine reserves are one management approach that could serve such intermediate strategists, providing refugia for colonisation, while protecting important large, fecund adults.