52 JUNE 2014 • WORLD AQUACULTURE • WWW.WAS.ORG The most successful studies have used decapod crustacean zoeae ranging from 0.01 to 1 zoea/mL (Iglesias et al. 2002), with a size representing 50-100 percent of paralarvae mantle length (Villanueva 1994) and large (>100-L) tanks ( De Wolf et al. 2011). Based on the search for appropriate logistical (accessibility and low cost) and zootechnical methodology (high fertility rate and easy rearing in captivity), new benthic prey have been tested recently, emphasizing mysids (Gastrosaccus roscoffensis), grass shrimp zoea (Palaemon elegans), eggs and zoea of the pandalid shrimp (Pleisonika narval), sea urchin larvae (Diadema aff. antillarum) and rock crab zoea (Grapsus adcensionis) (Fig. 5). Best results have been obtained with rock crab zoea, with 2.5 percent survival at 77 days of culture and one 10-g juvenile of 223 days old. Specific growth (5 percent) was less than values previously reported (7-9 percent) by Iglesias et al. (2004) but similar to those reported by De Wolf et al. (2011). Lipid Metabolism. Poor growth and high mortality observed during the planktonic stage of common octopus rearing seems to be associated with a nutritional imbalance in the lipid profile (Navarro and Villanueva 2000, 2003, Villanueva et al. 2004, Iglesias et al. 2007, Seixas et al. 2010). Therefore, it is essential to determine the metabolic needs of paralarvae for the success of commercial-scale octopus aquaculture. Assays are presently being performed using 14C-labelled fatty acids. In addition, similar research activities are being conducted with the main prey items (Artemia and G. adscensionis) used in octopus paralarvae culture. Stress Biomarkers Cultured paralarvae have a high sensitivity to handling, which may cause massive mortalities. Therefore, it is necessary to define and establish biomarkers that can help to further explore the requirements for successful rearing of these organisms. Biomarkers for the detection and quantification of stress are being selected to improve the rearing conditions of common octopus. Grow-out in Sea Cages Commercial-scale aquaculture of common octopus is currently restricted to grow-out of wild juveniles in cages. The lack of sheltered sea areas in the Canary Archipelago forced the design of a rearing system to meet the demanding conditions of the offshore environment. A pilot offshore cage platform with a capacity of 1.5 t was designed for the implementation of experimental trials (Fig. 6). Individuals were fed a diet of minced low-value fish and kept at a maximum density of 18 kg/m3. Grow-out tests in these cages resulted in good growth, survival and easy handling. Fisheries Management Age validation in common octopus beaks. As with other harvested species, age and growth determination is critical to understanding common octopus life history and to model the dynamics of wild populations for sustainable management. The identification and interpretation of growth increments in calcified structures can be used for exploited species of cephalopods (Fig. 7). Validation studies of the periodic deposition in hard structures of common octopus are as yet incomplete without known-age individuals; daily deposition has been confirmed only in some sizes (Canali et al. 2011). Laboratory experiments of chemical and environmental marking in wild specimens of all sizes have been conducted to confirm the daily deposition of beak increments across the age range of the species. It has also been used to age individuals of known age from paralarvae to adult. Beaks as stress biomarkers. The study of beak increment validation has highlighted the value of this structure as life recorders by observing environmental or biological stress marks (checks or stress increments) in the microstructure of beak sagittal sections, making it possible to detect stressful events during the lifetime of the animal. Therefore, stress marks in the beak microstructure could be a tool to assess stress related to handling and other events. Animal Welfare The European Directive 2010/63/EU for the protection of animals used for experimentation and other scientific purposes includes, for the first time, breeding of and experimenting with cephalopods in aquaculture research, inasmuch as there is scientific evidence of their ability to experience pain, suffering, distress and lasting harm. This directive promotes the identification and development of suitable methods of anaesthesia, analgesia and euthanasia. All experimental planning and design of culture facilities at the COC, including those involving octopus, are undertaken according to the baseline described in the directive. Thus, in the LEFT, FIGURE 6. Offshore octopus cage used in pilot study in the Canary Islands. RIGHT, FIGURE 7. Daily increments and two stress checks (darker increments to the right) in a sagittal section of Octopus vulgaris beak (200x).
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