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Restocking the sea cucumber Holothuria scabra: sizing no-take zones through individual-based movement modelling
Fisheries Research
  • Steven W Purcell, The WorldFish Center, New Caledonia
  • David S Kirby, Marine Resources Division, New Caledonia
Document Type
Publication Date
Peer Reviewed
The valuable sea cucumber Holothuria scabra, known as ‘sandfish’, has potential for restocking. However, there is little information available to determine the size of the no-take zones (NTZs) needed to protect the released animals so that they can form nucleus breeding populations. To do this, we measured short-term movement paths of released juvenile (1–105 g) and wild adult (130–690 g) sandfish in a seagrass bed in New Caledonia. We then developed an individual-based model (IBM) to predict long-term dispersal of sandfish released as juveniles (1–16 g) at 1 individual m−2 within a 1-ha area, drawing on distributions of speed and directionality and the relationship between speed and animal weight from field data. Movement was non-random at the sampling scale used, since animals tended to turn <90° at each 2-h time step. We examined high- and low-growth scenarios by applying 50% and 25% of the modelled growth rates of sandfish held in earthen ponds (where they are known to grow faster). The dispersal of released sandfish was predicted to be limited in the first 2 years, then markedly faster thereafter. After 10 years, 6–12% of surviving animals were predicted to remain in the original 1-ha release site. To protect surviving sandfish as nucleus breeding populations for 10 years, and accepting 10% spillover, square NTZs would need to be 19–40 ha. The findings are useful for the management of restocking and pre-defining the size of sites for recapture surveys. Our model allows user-specified values for future releases and should be applicable for other sedentary marine invertebrates where basic data on movement and growth are available.
Citation Information

Purcell, SW & Kirby, DS 2006, 'Restocking the sea cucumber Holothuria scabra: sizing no-take zones through individual-based movement modelling', Fisheries Research, vol. 80, no. 1, pp. 53-61.

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