Restoring small-scale fisheries for tropical sea cucumbers

Abstract

Overfishing threatens to extinguish local fisheries for valuable tropical sea cucumbers by reducing population densities to the point where reproductive success trails behind natural mortality (known as depensation or the ‘Allee effect’). Once this happens, conventional management measures alone, such as closed seasons/areas, size limits and gear restrictions, will usually fail to repair the damage. A different suite of active management interventions must be considered to restore the spawning biomass of severely over-exploited populations. These include: (1) restocking no-take zones with hatchery-reared juveniles; (2) aggregating remnant wild individuals in no-take zones; and (3) development of small enterprises to rear wild-caught sea cucumbers in simple sea pens, or dedicated sublittoral areas, to the size above sexual maturity that optimises earnings. The first intervention is currently limited to a few species of tropical sea cucumbers, whereas the second and third interventions can be applied to many species. The third intervention is particularly attractive – it allows fishers to add value to their catch, reverses the effects of fishing from damaging to improving the potential for replenishment by overcoming the Allee effect, and creates multiple groups of spawners to supply recruits throughout the range of the population(s) supporting a fishery.