Alternative diets for maintaining and rearing cephalopods in captivity

The requirement of live marine prey for cephalopod mariculture has restricted its practicality for inland research laboratories, commerical enterprises and home aquarists. We evaluated acceptability and resultant growth on: (a) frozen marine shrimps, (b) live and frozen marine polychaete worms, (c) live and frozen marine crabs, (d) frozen marine fishes, (e) live adult brine shrimp, (f) live freshwater fish and (g) live freshwater crayfish. The diets were presented for periods of 2 to 11 weeks to octopuses, cuttlefishes or squids and in most trials the results were compared to animals fed control diets of live marine shrimps, crabs or fish. Overall, frozen marine shrimp proved to be the best alternative diet tested. Adult Octopus maya on frozen marine shrimp diets grew as well as those on control diets at 2.8% body weight per day (%/d) compared to 2.0 %/d on live freshwater crayfish, 1.4%/d on live marine polychaete worms and 0.8 %/d on live freshwater fish (Tilapia sp.). Juvenile Octopus maya and Octopus bimaculoides also grew comparably to controls when fed frozen marine shrimps; growth rates ranged from near 3.0 %/d at 3 months of age to nearly 2.5 %/d at 6 months of age. Thus, these alternatives are acceptable as the octopuses end their exponential growth phase at an age of 3-5 months. Attempts to rear O. maya hatchlings and juveniles (up to 1 month of age) on dead foods resulted in high mortality and slow or negative growth. No live or dead alternative diet has been found yet that will promote good growth and survival in hatchling octopuses. Hatchling F3 generation Sepia officinalis (the European cuttlefish) were reared for 6 weeks exclusively on adult brine shrimp (Artemia salina). Survival, feeding rate and growth were excellent. This experiment marks the first time that brine shrimp have been used exclusively to successfully rear juvenile cephalopods. Juveniles readily accepted frozen marine shrimp at 3 months of age, and growth over 2 months was 3.3 %/d versus 3.9 %/d on live shrimp. Gross Growth Efficiency (GGE) was 39% and 43%, respectively. Twenty-five slightly older cuttlefish, group-reared for 69 days on a diet of frozen marine fishes, grew at 2.5 %/d with a mean GGE of 38%. These data compare well to published data from live diets. The bay squid Lolligucula brevis was trained over an 8-day period to accept frozen marine shrimps. Over 41 days, growth was 1.3%/d versus 1.8 %/d on live shrimp. These results provide researchers and others some viable alternative foods for maintaining or rearing cephalopods through a substantial portion of their life cycle.