WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2014 51 phytoplankton (Iglesias et al. 2006). New Artemia enrichment protocols are being developed based on the use of liposomes to enhance dietary lipid components (Fig. 4). Inert diets. An artificial microdiet eliminates costs related to logistics, management and cultivation of live prey, while allowing better control of the feed nutritional content. However, preliminary experiences using microdiets were not promising, probably related to acceptability, palatability, floating/sinking, loss of nutrients and/ or manufacturing processes (Domingues et al. 2001). Current research focuses on the development of inert diets using different raw materials and binding agents that produces a water-stable diet, reduces waste and improves management efficiency. Alternative Live Prey Species. Decapod crustacean larvae are probably one of the main natural prey of planktonic common octopus paralarvae (Roura et al. 2010) and most successful longterm rearing trials in the laboratory have been obtained when crustacean larvae are the primary prey (Villanueva and Norman 2008), resulting in the best survival and settlement rates (Iglesias et al. 2007). Decapod larvae have several advantages compared to other live prey, including good acceptability and appropriate nutrient profile. However, several problems have arisen from its use, such as the need for a parallel culture, infeasibility at commercial scale and increased culture cost. The best paralarvae performance has been achieved in tanks of 500-1,000 L (De Wolf et al. 2011, Sánchez et al. 2011). A second line of work has applied the best results obtained from 100-L tanks to 500-L tanks, because larger volumes allow better growth and longer-term experiments, until settlement in the best case. Rearing of octopus paralarvae is currently being carried out at the COC using flow-through systems with filtration consisting of three inline mesh filters and ultraviolet disinfection. Tanks are under a light regime of 150-200 lux with 6500 K normal white fluorescent light, and a photoperiod of 12L:12D in black tanks. To improve survival, paralarvae density has been reduced to 3-5 individuals/L with moderate (lateral) aeration. Paralarval Nutrition Artemia enrichment. Poor performance, inconsistent growth and a lack of settlement has been obtained when Artemia is used as prey for octopus paralarvae. These adverse results could be explained by an imbalanced nutrient profile that does not meet paralarvae needs, and a relatively small size (0.45 mm total length) of Artemia nauplii that is not suitable for paralarvae greater than 15 days old. Paralarvae feeding experiments with Artemia have been undertaken recently using Artemia juveniles (1.5-2 mm long) with (CONTINUED ON PAGE 52) TOP LEFT, FIGURE 2. Culture facilities at Oceanographic Centre of the Canary Islands (COC). TOP RIGHT, FIGURE 3. Tanks (100 L) for rearing common octopus paralarvae. BOTTOM LEFT, FIGURE 4. Artemia culture tanks. BOTTOM RIGHT, FIGURE 5. Grapsus adscensionis culture tanks.
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