ALBERT

Description: The effects of feeding a prepared surimi diet (fish-based) and a prepared pelleted diet (shrimpbased) on the survival, growth and feeding rate of the cuttlefish Sepia officinalis L. were evaluated during a 45-day experiment. One hundred and twenty juveniles of laboratory cultured cuttlefish (74.5 ± 12.36 g) were divided into three treatments and were fed thawed shrimp (control), pellets or surimi. Survival rates on these diets were 95.0%, 67.5% and 22.5%, respectively. Preliminary data indicated that the low survival of cuttlefish fed surimi may have been caused by low levels of copper in their blood (131 vs 244 μg/ml) since copper is required for their respiratory blood pigment, hemocyanin. Instantaneous growth rates were 2.71 % body weight BW/day for cuttlefish fed raw shrimp, 0.33% BW/day for cuttlefish fed pellets, and 0.54% BW/day for cuttlefish fed surimi. The feeding rate of cuttlefish fed shrimp was high (6–8% BW/day). The feeding rate on pellets increased with time (from 〈 1 to 3% BW/day) but never reached the level for raw shrimp. The feeding rate on surimi increased to equal the rate for raw shrimp during days 1–30 (8 to 9% BW/day) and thereafter decreased (〈4% BW/day). In conclusion, there was a major distinction between the palatability of a prepared diet and the ability of that diet to support growth. Surimi was highly palatable but resulted in poor survival, suggesting low nutritional quality. In contrast, pellets were less palatable but produced maintenance growth. Development of practical surimi diets will require supplementation of the surimi with soluble micro- and macronutrients.

Description: Octopus digueti Perrier and Rochebrune, 1894 was reared through its life cycle at 25°C in a closed seawater system using artificial sea water. Two field-collected females produced 231 hatchlings: 193 hatchlings were groupcultured while 24 were isolated at hatching and grown individually to allow precise analyses of growth in length and weight over the life cycle. All octopuses were fed primarily live shrimps. Maturing adults fed at a rate of 4.7% of body weight per day and had a gross growth efficiency of 48%. Growth in weight was exponential for the first 72 days and described best by the equation: WW(g) = .0405e•0646t. The mean growth rate over this period was 6.4% increase in body weight per day (%/d), with no significant difference between male and female growth. From 72 to 143 days, growth was logarithmic and described best by the equation: WW(g) = (6.78 x 1O- 6) t3 .13. Females grew slightly faster than males over this growth phase. During the exponential growth phase, mantle length increased at a mean rate of 2.1% per day, declining to 1.1% per day over the logarithmic phase. No attempt was made to describe mathematically the period of declining growth rate beyond day 143. The primary causes of early mortality in group culture were escapes and cannibalism. Survival was good despite high culture density: 73% survival to date of first egg laying (day 111). Survival was better among the isolated growth-study octopuses: 88% to the date of first egg laying (day 130). Mean life span was 199 days in group-reared octopuses and 221 days in the growth-study octopuses. There was no significant difference between male and female life span. Progeny of the group culture were reared at similar stocking densities and fed predominantly fresh dead shrimp and crab meat. This diet resulted in cannibalism, with only 6% survival to first egg laying on day 128. Fecundity in this group was lower. Octopus digueti is a good candidate for laboratory culture and biological experimentation because of its small size, rapid growth, short life span, and good survival in group culture.