Restocking the sea cucumber Holothuria scabra: Sizing no-take zones through individual-based movement modelling

Authored by Steven W Purcell, David S Kirby

Date Published: 2006

DOI: 10.1016/j.fishres.2006.03.020

Sponsors: French government Australian Centre for Inter- national Agricultural Research

Platforms: No platforms listed

Model Documentation: Other Narrative Pseudocode Mathematical description

Model Code URLs: Model code not found

Abstract

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 (130-690g) 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 degrees 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. (c) 2006 Elsevier B.V. All rights reserved.

Tags

fisheries growth Australia Biology Reef Reserves Stock enhancement Solomon-islands Echinodermata