WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2012 43 (Table 2). The addition of commercial algae Porphyra was the most preferable among additional algae as an attractant and was as attractive as biofilm. Opihi preferred diets with biofilm or Porphyra. Growth Performance on Artificial Feed The abalone literature was studied for insights on developing an artificial feed for opihi, inasmuch as there have been no studies on opihi feed. In initial work, casein was used as base ingredient to generate standard diets for abalone (Uki et al. 1985a, 1985b, Uki and Watanabe 1992). Subsequently semi-purified and practical diets supplemented with crystalline amino acids were used for abalone feed, following the hypothesis of Ako and Dominy (1987) that the amino acid profiles of diets should be modeled after the amino acid profiles of animal tissue if requirements are unknown (Mai et al. 1995, Coote et al. 2000, Sales et al. 2003, Cho et al. 2008, Cho 2010). Essential amino acid profiles of macroalgae do not match essential amino acid profiles of abalone (Mai et al. 1994, Cho et al. 2008, Naidoo et al. 2006, Bautista-Teruel et al. 2003) and macroalgae diets do not support good growth of abalone. Cho et al. (2008) and Cho (2010) tested different protein ingredient sources. Several diets had amino acid profiles that matched animal amino acid profiles. However, differences in the performance of some diets might be explained by differences in diet palatability, which was not evaluated by the authors. Two diets were examined in another feeding trial. These consisted of soybean meal (29 percent) and corn gluten (18 percent). Lysine was boosted with fishmeal (20 percent) rather than crystalline amino acids. The other diet contained fish meal (25 percent), soybean meal (20 percent) and krill meal (13 percent). A fishmeal (35 percent) only diet was used as a control. All diets contained commercial algae (Porphyra tenera or nori at 14 percent) as a feed stimulant. A package of common ingredients was included, consisting of alginate (5 percent), corn oil/menhaden oil (1/0.3; v/v), vitamin mix (1 percent plus choline and inositol), and cholesterol (0.4 percent). In all diets, wheat flour was used to round out the formulation to 100 percent dry ingredients. Two control treatments were also included: a natural feed, biofilm, and an alternating feeding of soy/corn/fish diet with biofilm. The artificial feed was fed four days and then the live algae feed was fed for four days. Naidoo et al. (2006) reported that abalone Haliotis midae grow well on a mixed diet of formulated feed and live algae. Opihi gained weight in all treatments (Table 3) but the greatest weight gains of 27 percent and 29 percent BW in the 10 weeks period for opihi fed with the fish/soy/krill and alternating diets, respectively, and were significantly higher than that of opihi fed with other diets. These growth rates were good and indicate the promise of commercial culture. Opihi growth on the control biofilm diet was poor. The fish/soy/krill diet supports the feed palatability hypothesis. Growth rates of opihi were proportional to feed consumption. Fish/soy/krill diet was the most preferable with the highest feeding amount (0.73 percent DM/BW/day) among the formulated diets, whereas the control fishmeal diet was the lowest in feed consumption. Conversely, consumption of the biofilm diet was the greatest (0.81 percent DM/BW/day) of all diets tested, but growth was poorest, possibly because of the lack of some essential amino acid in biofilm. Biofilm may provide some unknown nutrients that could produce better growth in animals fed the alternating diet. The weight gain of opihi fed with an alternating diet of soy/fish/corn gluten and biofilm was significantly greater than that of opihi fed soy/fish/corn gluten only. A combination of the formulated diet and natural food might be desirable for aquaculture of opihi until the unknown nutrient is discovered. Feeding frequently in all diets was about 45 percent of the total number of feeding days (approximately one feeding every two days). Survival of opihi fed the alternating diet was greatest (71 percent). Concluding Remarks For the Hawaiian limpet, a new species for aquaculture, we immediately encountered challenges relating to the behavior of clinging tightly to surfaces. To collect and transfer opihi from one container to another, plastic sheets or soft plastic colanders were used to handle opihi without transfer mortality. Cultivating natural food in the laboratory allowed us to hold opihi and learn about feed preferences. Opihi feed well on biofilm, which was the key to good feed consumption when incorporated into artificial feed. Commercial brown algae Porphyra, known as nori, can replace biofilm as a feeding stimulant. Opihi survived well on prepared diets. Growth performance trials suggest that formulated diets of fishmeal, soybean meal, and krill and alternating diets of soybean meal, corn gluten, and fishmeal with biofilm produced the best growth rates and feed intake over 10 weeks. These diets could form the basis for a formulated feed for commercial aquaculture of opihi. In subsequent work, these diets will allow us to hold opihi indefinitely for more grow-out studies and spawning and larval rearing trials. Notes 1 Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa 1955 East West Road, Room 218, Honolulu, Hawaii 96822, USA. Please address correspondence to the senior author. 2 Trimaco, Durham, NC 3 Covalence Plastics, Minneapolis, MN 55431 4 Aquatic Ecosystems, Apopka, FL 32703-7730 5 GABA, Sigma Chem. Co., St. Louis, MO, USA 6 www.sunheat.cn/en/index.asp References Ako, H. and W. Dominy. 1987. The amino acid requirements of Penaeid shrimp. University of Hawaii Sea Grant Quarterly 9(4):1-8. Bautista-Teruel, M.N., A.C. Fermin and S.S. Koshio. 2003. Diet development and evaluation for juvenile abalone, Haliotis asinina: animal and plant protein sources. Aquaculture 219:645-635 (CONTINUED ON PAGE 42)
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