42 DECEMBER 2012 • WORLD AQUACULTURE • WWW.WAS.ORG water movement. Water quality parameters were temperature 24.0-25.5 C, pH 7.9-8.6 and the D.O. 5.5-6.2 mg/L. More fish meal-soybean meal diet was consumed than the soybean meal-corn meal diet (Table 1). Animals fed relatively frequently on these diets, ranging from an average of 54 percent and 46 percent of days tested, respectively. The attractant betaine did not improve consumption of either diet and diets with betaine were consumed in much lower quantities and less frequently than the fish mealsoybean meal diet. Potential feeding stimulants such as GABA, DMPT and Spirulina did not improve feed consumption or increase feeding frequency. The diet incorporating biofilm was significantly preferred and the animals ate relatively frequently (53 percent of the nights) while diets containing Spirulina rather than biofilm were not as well eaten. Biofilm could be a key cue for enhancing feeding. In follow up trials, biofilm was confirmed as a feeding stimulant (Table 2). Fish meal at twice (30 percent) the original level was tested and it was not an added feeding stimulant. Removing biofilm drastically and significantly decreased feeding. Biofilm was unstable and sometimes cultures had to be restarted. Trials were done to replace biofilm with various products, including 1) commercial algae (Porphyra tenera or P. yezoensis) at 14 percent 2) Norwegian kelp (Ascophyllum nodoscum), 3) commercial brown algal kombu (Laminaria japonica), and 4) fresh ogo (Porphyra parvispora) TABLE 1. Feed consumption (%DM/BW/day) of different diets fed to opihi. Trial Base diet Additive Feed consumption 1 FM/SBM 0.16±0.06 a SBM/CM 0.10±0.03 ab FM/SBM Betaine 0.03±0.05 b SBM/CM Betaine 0.01±0.01 b 2 FM/SBM 0.07±0.12 b FM/SBM Biofilm 0.17±0.19 a FM/SBM GABA 0.08± 0.11 b FM/SBM DMPT 0.04±0.07 bc FM/SBM Spirulina 0.02±0.01 c 3 FM/SBM Biofilm 0.08±0.03 a High FM/SBM Biofilm 0.07±0.01 a High FM/SBM 0.01±0.01 b High FM/SBM Porphyra1 0.09±0.04 a High FM/SBM Kelp2 0.04±0.03 ab High FM/SBM Ogo3 0.03±0.03 b High FM/SBM Kombu4 0.03±0.03 b FM=fishmeal, SBM=soybean meal, CM=corn meal. For means within a column, different letters indicate significant (P<0.05) differences by one-way ANOVA. Letters indicating significant differences apply within individual trials only and not across trials. 1 Nori or red algae Porphyra tenera or P. yezoensis (Nishimoto Trading Co. Ltd., Korea). 2 Norwegian kelp Ascophyllum nodoscum (Oceanic Institute). 3 Ogo or the red algae Gracilaria parvispora. 4 Kombu or the brown algae Laminaria japonica (Nishimoto Trading Co. Ltd., Japan) TABLE 2. Weight gain (g), specific growth rate (%/day), feed consumption (%DM/BW/day), survival (%) of opihi fed different diets for 10 weeks. Experimental diets Weight gain SGR Feed consumption Survival SBM/CM/FM 0.76±0.45b (8.5) 0.12±0.07 a 0.18±0.07 a 67 FM/SBM/krill 1.80±1.38a (27) 0.73±0.53 b 0.73±0.53 b 67 FM 0.78±0.88b (6.9) 0.11±0.13 a 0.14±0.04 a 40 Alternating diet* 1.58±0.62a (29) 0.44±0.19 b 0.26±0.15 a 71 Biofilm 0.38±0.4b (2.0) 0.10±0.11 a 50 FM=fishmeal, SBM=soybean meal, CM=corn meal. For means within a column, different letters indicate significant (P<0.05) differences by one-way ANOVA. *Alternating diet of soy/corn gluten/fish with biofilm at 4-day intervals for each diet. The giant opihi lives in deep water, not on wave-splashed rocks. Giant and yellow-foot opihi were collected in remote areas of the Hawaiian Islands. Opihi have evolved to cling tightly to rocks in high-energy water. Opihi are called fish of death because they are dangerous to collect. Every year people collecting opihi are swept off the rocks and drown.
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