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MEPS prepress abstract   -  DOI:

Limited long-term movement and slow growth of the sea cucumber Pearsonothuria graeffei

Alison R. Hammond, Steven W. Purcell*

*Corresponding author:

ABSTRACT: Sea cucumbers are heavily exploited worldwide yet data are lacking on animal mobility and life-history parameters for fishery management and conservation planning. This study assessed movement and growth rates for a medium-sized holothuroid, Pearsonothuria graeffei, harvested throughout the Indo-Pacific. We used photographic mark-recapture to track long-term movements and growth for this species over two years. Recapture rates were 67–72%. Movement rates averaged 9 m yr-1 and many individuals were found in aggregations and recaptured there again in two successive years. Growth was highly variable; smaller animals (<700 g) tended to gain weight while larger animals (>700 g) tended to lose weight. Some individuals lost weight and then regained weight, and vice versa for others. Growth models estimated that P. graeffei approach their average maximum weight (W: 769 g) in 7–12 yr and are slow-growing (growth coefficient K: 0.17). Natural mortality (M: 0.48 yr-1) was low, and estimated longevity (tmax) was 18 years. Pearsonothuria graeffei exhibits traits that heighten its vulnerability to overfishing: aggregation behaviour, low mobility, slow growth, a long lifespan, and low natural mortality. The site fidelity and low mobility infer that a system of small reserves would effectively protect breeding populations and that emigration to new sites is very limited. This study provides the first published evidence from natural habitats that holothuroids can lose and later regain weight. Our empirical findings suggest that small to medium-sized holothuroids might be slower growing and longer lived than previously believed, imploring a more conservative conservation policy.