International Journal of Marine Science, 2024, Vol.14, No.3, 245-254 http://www.aquapublisher.com/index.php/ijms 251 Holothuria polii was induced to spawn using thermal shock, which proved effective in obtaining healthy gametes, with larvae reaching the pentactula stage in 10 days (Rakaj et al., 2019). Holothuria tubulosa also responded well to thermal stimulation plus thermal shock, with larvae reaching the juvenile stage in 27 days (Rakaj et al., 2018). For the tropical species Stichopus monotuberculatus, a modified low-temperature stimulation method was more suitable for inducing spawning, resulting in a detailed record of gonadal and embryonic development (Cheng et al., 2021). These methods highlight the importance of optimizing spawning induction techniques to improve breeding success across different sea cucumber species (Wang et al., 2022). 6.2 Larval rearing practices Larval rearing practices are crucial for the successful aquaculture of sea cucumbers. For Holothuria polii, three different microalgal feeding regimens were tested, with the highest concentration (20,000~40,000 cells/mL) proving most effective, resulting in 14% of larvae metamorphosing into settled juveniles (Rakaj et al., 2019). In the case of Holothuria leucospilota, a combined diet of microalgae (Chaetoceros muelleri) and yeast (Saccharomyces cerevisiae) at a 3:1 ratio was found to be optimal, significantly improving larval survival, growth, and development (Yu et al., 2022). For Stichopus monotuberculatus, diets supplemented with digestive enzymes such as α-amylase, cellulase, and trehalase improved larval survival rates and settlement rates significantly compared to control groups (Cheng et al., 2021). These findings underscore the importance of diet optimization in larval rearing to enhance survival and growth rates. 6.3 Restocking strategies Restocking strategies involve the release of hatchery-reared juveniles into natural habitats to replenish depleted populations. For Holothuria scabra, experimental releases of juveniles into seagrass meadows in Papua New Guinea showed varying levels of success depending on the site and protection measures, with significant differences in juvenile growth observed between sites (Hair et al., 2016). Similarly, an 8-month sea ranching study for Stichopus monotuberculatus in a tropical coral reef island area in China demonstrated the feasibility of this approach, with juveniles reaching commercial size within the first year, although high mortality was observed in the first month post-release (Xu et al., 2022). These studies highlight the potential of sea ranching and restocking as viable strategies for sustainable sea cucumber aquaculture, while also emphasizing the need for site-specific assessments and acclimation procedures to improve survival rates. By integrating optimized breeding techniques, effective larval rearing practices, and strategic restocking approaches, sustainable tropical sea cucumber aquaculture can be achieved, contributing to the conservation of natural populations and meeting market demands. Further research and refinement of these methods are essential to address the challenges and improve the overall success of sea cucumber aquaculture programs. 7 Environmental and Socio-Economic Impacts 7.1 Ecological considerations 7.1.1 Assessing ecosystem health The health of ecosystems where sea cucumber ranching is implemented is a critical factor for the success and sustainability of these operations. Studies have shown that sea cucumber ranching can contribute positively to ecosystem health by alleviating overfishing pressures on natural populations and enhancing the ecological balance. For instance, the sea ranching of Stichopus monotuberculatus in the South China Sea demonstrated that sea cucumbers could grow to commercial size within a year, suggesting that ranching can help relieve stress on natural populations and protect coral reef ecosystems (Xu et al., 2022). Additionally, the integration of sea cucumbers in multi-trophic aquaculture systems has been shown to have bioremediation potential, reducing particulate waste and benthic impacts, although the scale of sea cucumber production needs to be significantly increased to achieve substantial environmental benefits (Chary et al., 2020). 7.1.2 Evaluating economic benefits The economic benefits of sea cucumber ranching are multifaceted, encompassing direct financial gains from harvests and broader socio-economic impacts. In the Philippines, communal sea ranching projects have generated various livelihood benefits, although substantial economic returns from harvests were not always realized, leading
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