World Aquaculture - June 2023

48 JUNE 2023 • WORLD AQUACULTURE • WWW.WAS.ORG Canada have been studying IMTA with various species of sea cucumbers for several decades but lack the appropriate policies to allow the development of commercial IMTA and/or sea cucumber culture. Cost-effective containment systems for housing sea cucumbers beneath other aquaculture facilities also requires further study at the level of individual species to maximize the growth and stocking density, minimize the stress of sea cucumbers held within them and to allow segregation of wild and cultured sea cucumbers. Given differences in size, metabolism, feeding rates and bioturbation rates, there likely is not a one-size-fits-all approach for optimal stocking densities and containment methods for all sea cucumber species. Despite these challenges, sea cucumbers represent an incredible opportunity to improve the productivity and economic/ environmental sustainability of aquaculture endeavors around the globe. We expect to see greater inclusion of these fascinating organisms in commercial aquaculture in the future. Notes Emaline M. Montgomery* and Christopher M. Pearce, Fisheries and Oceans Canada, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, British Columbia, V9T 6N7, Canada * Corresponding author 1 Montgomery, unpublished data References Abisha, R., K. K. Krishnani, K. Sukhdhane, A. K., Verma, M. Brahmane and N. K. Chadha. 2022. Sustainable development of climate-resilient aquaculture and culture-based fisheries through adaptation of abiotic stresses: a review. Journal of Water and Climate Change 13(7): 2671-2689. Ahlgren, M.O. 1998. Consumption and assimilation of salmon net pen fouling debris by the red sea cucumber Parastichopus californicus: implications for polyculture. Journal of the World Aquaculture Society 29(2):133-139. Cubillo, A.M., J.G. Ferreira, J. Lencart-Silva, N.G. Taylor, A. Kennerley, J. Guilder, S. Kay and P. Kamermans. 2021. Direct effects of climate change on productivity of European aquaculture. Aquaculture International 29:1561-1590. Engelhard, G.H., E.L. Howes, J.K. Pinnegar and W J. Le Quesne. 2022. Assessing the risk of climate change to aquaculture: a national-scale case study for the Sultanate of Oman. Climate Risk Management 35:100416. Feng, X., H. Li, Z. Zhang, T. Xiong, X. Shi, C. He, Q. Shi, N. Jiao and Y. Zhang. 2022. Microbial-mediated contribution of kelp detritus Sea Cucumbers and Ocean Acidification There is little doubt that IMTA has the potential to increase the productivity and ecological sustainability of farming aquatic organisms, but how resilient will these systems be in the face of changing global climate? The Intergovernmental Panel on Climate Change (IPCC) predicts that over the next 100 years, average global air temperatures are expected to increase 1.5 C and seawater pH is expected to drop from around 8.0 to 7.6 (IPCC 2022). The effects of ocean acidification and warming are already being felt worldwide and are expected to have direct effects on aquaculture (Cubillo et al. 2021). Diverse mitigation strategies have been proposed to help future-proof world aquaculture, including identifying the most at-risk species, shifting farming focus to lowertrophic-level species, selective breeding, nutritional supplements and increased reliance on closed or near-closed systems (Abisha et al. 2022, Engelhard et al. 2022). Interestingly, sea cucumbers may have a solution for the mitigation of local climate effects at farm sites that is derived from an unlikely source. Preliminary evidence from tropical sea cucumber species suggests that their faeces are slightly alkaline and that they can provide local pH buffering for calcifying organisms such as corals (Williamson et al. 2021, Wolf et al. 2017). These local benefits might also be applied to calcifying bivalves grown alongside sea cucumbers in IMTA systems. Many questions remain, including the scale at which this benefit might be received and if temperate sea cucumber species might also be able to provide such services. The inclusion of macroalgae into IMTA systems has also been proposed as a multifaceted solution to improve the sustainability of aquaculture through carbon sequestration, amelioration of eutrophication and improved oxygenation (Gao et al. 2022, Hurd et al. 2022, Zhang et al. 2022). Although still a bit controversial (see Gallagher et al. 2022, Macreadie et al. 2019), there is a growing body of evidence to suggest that kelp culture in higher latitude regions would still provide some carbon sequestration as sea surface temperatures continue to increase (Feng et al. 2022, Filbee-Dexter et al. 2022), especially when nitrate levels are enriched, such as around aquaculture tenures (Fernandez et al. 2020). As a result, including kelp and sea cucumbers in IMTA systems could prove useful in some situations and regions for mitigating the effects of ocean acidification and hypoxia associated with warming. Barriers to Incorporation Adding sea cucumbers to already existing farms seems intuitive, but there are a few barriers that need to be solved before this practice could be applied universally. Some countries like FIGURE 2. Apostichopus californicus (contracted length 20 cm) feeding on biofouling material growing on nylon fish containment netting (panel A) using their pancake-like tentacles (yellow ellipse in panel B). Scale bars indicate 4 cm.