WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2013 21 (CONTINUED ON PAGE 22) marine resources by communities and local governments (JunioMenez et al. 2012). Three sandfish ranching sites have been developed in northwest Luzon where the rights-holders are 12-15 families endorsed by the local government (Junio-Menez et al. 2012). Sandfish are released into a strict NTZ (1 ha), surrounded by a 4-ha reserve where traditional fishing activities (except harvesting of sea cucumbers) are permitted by the rights-holders (Junio-Menez et al. 2012). Sea ranching is currently one of the most extensive forms of sea cucumber aquaculture, typified by the designation of a large area of seagrass beds (~ 5 ha), low survival (2-39 percent) and low yields (58.4-220 kg/ha) (Junio-Menez et al. 2012). To facilitate monitoring of the stock after release, juveniles (5-7 g) are often stocked into a sea pen. Growth rates generally range from 1.0-1.8 g/d but can be highly variable, depending on the quality of the site and micro-scale changes in habitat (Purcell and Simetoga 2008, Junio-Menez et al. 2012). Associated costs are currently funded by donor agencies because the project is in the early stages and the overarching objective remains restocking wild populations. Constraints and threats to sea ranching projects are related to natural disasters (e.g., typhoons) that have the potential to destroy sea pens, modify habitat and damage hatchery infrastructure, and poaching that threatens economic viability (Hair 2012, Junio-Menez et al. 2012). Encouragingly a mass spawning event was observed by researchers in February 2010 at sea cucumber ranches in northern Luzon, indicating that released hatchery-reared juveniles had indeed formed a viable spawning population (Junio-Menez et al. 2012). Sea-Pen Farming in Madagascar In coastal regions in southwest Madagascar, semi-nomadic fishers known as the Vezo, have little or no direct control over adjacent nearshore resources. Under these circumstances, the concept of sea-pen farming is attractive because the construction of a pen, in an area designated by the broader community as suitable for aquaculture, can to a certain extent, define user rights and confer ownership. The model of ownership that evolved in Madagascar was at the level of the nuclear or extended family. Initially pen materials were supplied and a private company (Madagascar Holothurie S.A.) supplied farmers with hatcheryreared juveniles at US$ 0.20/individual. Capital inputs were initially subsidized or funded by donor agencies until farmers became established and successful, after which the model shifted to devolve responsibility to the farmers. Farmers constructed pens of 225 to 600 m2 in nearshore seagrass beds using locally available material such as nylon fishing nets and wood (Fig. 7). Hatchery-reared juveniles (10-15 g) were stocked at 0.5/m2. Survival rates from the initial trials ranged from 35 to 80 percent. However, in areas prone to predation from crabs, survival was increased by releasing juveniles into protected nursery enclosures situated within pens until they reached ~50 g and were better able to withstand predation (Fig. 8, Robinson and Pascal 2012). Growth rates ranged from 1.0 to 1.8 g/d and were linked to seasonality and the carrying capacity of the site. At some sites, market-size sea cucumbers of 300 g were produced after only 5 to 8 months (Fig. 8). Assessment of site carrying capacity using test plots is recommended because some sites are not viable while others are capable of supporting densities of 700 g/m2 (Robinson and Pascal 2012). Sea pens can be considered to be a semi-intensive form of small-scale aquaculture because they offer greater control over initial site selection, controlling predation, monitoring and harvesting of stock, although at present no additional feed or fertilizers are used. In the first few years of development, the main challenge that faced sea-pen farming in southwest Madagascar was poaching related to an inherent weakness in the business model. It was more profitable for famers to sell sea cucumbers to traders in nearby villages than honor their agreement and sell market-size sea cucumbers back to the company that provided juveniles (Robinson and Pascal 2012). Other constraints to developing sea pens are the capital outlay needed to buy materials and the availability of trained extension workers to accompany farmers through the first few farming cycles. Pond Culture in Vietnam Substantive research on sandfish aquaculture has been FIGURE 5. Hapa nets used for ocean nursery of sandfish juveniles in Philippines. Photo: G. Robinson. FIGURE 6. Hapa nets used for nursery culture in Vietnam. Photo: D. Mills
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