WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2012 41 Formulated Diets: Feed Ingredient Palatability Trials Sea urchin feeds were used in initial feed ingredient preference tests. Fishmeal and squid meal were preferred over squid and mussel homogenate-based feeds, but results were unsatisfactory because survival rates were low. A diet containing fish meal (15 percent) and soybean meal (10 percent) to represent marine carnivore sensory cues was prepared. Another diet contained herbivore sensory cues and consisted mainly of soybean meal (35 percent) and corn meal (10 percent). A package of common ingredients was included, consisting of Spirulina (14 percent), alginate (9 percent), corn/menhaden oil (3 percent), vitamin mix (1 percent plus choline and inositol) and cholesterol (0.4 percent). In all diets, corn starch was used to round out the formulation. In some cases an additional 18 percent gelatin or 12 percent agar binder was used. Gelatin and alginate were gelatinized in boiling water before mixing with other dry ingredients (1:2; v/v). The feed paste was shaped into sheets of about 1.0 mm thickness. Sheets were cut into 1.2 cm2 pieces, which were sealed in plastic sample bags and stored at -20 C until used. In some diets, feeding stimulants were added, including betaine (2 percent), gamma aminobutyric acid5 at ten times the recommended dose (0.45 µM), and dimethyl propiothetin6 (DMPT) at 0.1 g/g, the recommended dose. Other feeding stimulants tested were biofilm at 14 percent dry matter, and in one trial, Spirulina was replaced with biofilm. At least six individuals were tested with each feed. Animals were fed in the late afternoon and uneaten feed was measured the next morning. Feed consumption was calculated as percentage of dry matter (DM) per bodyweight (BW) per day. The experiment was run for 7 days for each diet. An aquarium biofilter system was used (580 L/hr) to simulate (CONTINUED ON PAGE 40) FIGURE 1. The three common species of opihi. At top left, with dark green border, is the black-foot opihi (Cellana exarata). The yellow-foot opihi (Cellana sandwicensis) is to the right. At bottom left is the giant opihi (Cellana talcosa). FIGURE 3. Rough-water opihi habitat at Kalapaki Circle, Lihue, Kauai. FIGURE 2. Native Hawaiian eating some recently collected opihi. The limpet is an iconic food to Native Hawaiians. Photo: Jan TenBruggencate FIGURE 4. Experimental colander with an opihi. The small square is a piece of feed.
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