WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2014 47 detach juvenile sea cucumbers. Juveniles in the present study were detached using a soft scrubber brush. While in the trough tank (Fig. 9), juveniles were fed a slurry of a mixed diet of commercial Algamac-3050®1, flaked Schizochytrium sp. and sugar kelp Saccharina latissima in static seawater. The flaked Algamac® was mixed with seawater in an electric blender until completely emulsified. Kelp was collected locally and frozen in plastic bags at approximately -17 °C. Kelp was thawed and ground with a tissue homogenizer before feeding to juveniles. Environmental Aspects Perceptions of environmental problems associated with aquaculture vary among regions and countries of the world (Tacon and Forster 2003). Interactions between cultivated and wild P. californicus are of potential concern in BC (DFO 2013). However, if indigenous species and local broodstock are selected and individuals are grown under a containment system that keeps cultivated stock in and wild stock out, there should be only minor concern with the risk of potential escapes and their interaction with wild sea cucumbers. Like many holothuroids, the California sea cucumber is a deposit feeder, primarily consuming decaying plant and animal organic matter. Culture of this species is expected to be environmentally benign in terms of feed requirements, inasmuch as large quantities of animal protein are not necessary. If grown in combination with cultured finfish or bivalves (Fig. 10), sea cucumbers may not require external feed input at all, able to survive and grow by feeding on faeces and uneaten feed from finfish culture or faeces and pseudofaeces from bivalve culture. In such a scenario, sea cucumbers are environmentally beneficial because they reduce benthic accumulation of organic matter and thus aid in bioremediation of aquaculture sites (Paltzat et al. 2008, Hannah et al. 2013), while producing a secondary cash crop as part of Integrated Multi-Trophic Aquaculture (IMTA). Under these conditions, growth of sea cucumbers may be enhanced. For example, muscle growth of California sea cucumbers reared inside floating net pens at a salmon Oncorhynchus sp. rearing facility was significantly greater than that of sea cucumbers feeding in their natural environment (Ahlgren 1998). Similarly, the growth rate of California sea cucumbers held beneath sablefish Anoplopoma fimbria net pens was greater than in those grown at a control site away from the fish farm (Hannah et al. 2013). Sea cucumbers may be an ideal group of animals for cultivation in IMTA for crop diversification and environmental bioremediation. Conclusions The California sea cucumber has a suite of attributes that makes it an ideal candidate for aquaculture, including: • Dependence on primary productivity or decaying secondary productivity throughout its life cycle, • Good growth on natural and prepared diets in captivity, • Can be spawned throughout the year, • Larvae and juveniles are relatively easy to rear, • Relatively sedentary nature and can be reared in simple enclosures, • Can be reared with finfish or bivalves, feeding on their faeces and uneaten feed, • Fetches relatively high prices in well-established export and local markets. Further research is required to determine the effects of: • Temperature and diet on brood stock conditioning and larval/ juvenile growth and survival, • Stocking density on larval/juvenile growth and survival, • Nutritional values of natural and prepared diets for larvae, juveniles and adults, • Containment system design on juvenile/adult growth and survival, • Finfish and shellfish aquaculture wastes on growth, survival and product quality of sea cucumbers grown in IMTA systems. LEFT, FIGURE 9. California sea cucumber juveniles in a rearing tank. RIGHT, FIGURE 10. California sea cucumbers (red forms) on scallop lantern nets. (CONTINUED ON PAGE 48)
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