Raising and Rearing Octopus briareus

<< Cephalopod Articles | By Dr. James B. Wood

Octopuses make fascinating pets for advanced marine aquarists. Some of these cephalopods can even be reared from egg to adult in the comfort of your home; just be sure to check with your spouse before you decide to turn the den into a full scale rearing facility for 200 octopuses!

Octopuses have two reproductive strategies. The common octopus, Octopus vulgaris, lays 100,000 to 500,000 small eggs that hatch into planktonic young. O. briareus, on the other hand, lays approximately 500 large eggs which hatch into benthic young (Sweeney 1992). This fact is important as the large-egged octopuses are much easier to rear.

Occasionally an octopus will lay eggs in captivity. If the hobbyist has had the octopus for a long time, the eggs will be infertile. Usually the female will still brood the eggs and refuse food. She may eventually eat the infertile eggs. An octopus that lays eggs, whether they are fertile or not, is near the end of it's life. If an octopus that lays eggs was purchased or collected in the last 3 months or so, there is a good chance that the eggs will be fertile.

The best way to "stack the odds" of getting a female octopus that will lay fertile eggs is to go out and collect one yourself. Be sure to check local fishing laws first. In order to do this you need access to the ocean, an idea of when mature females are available in your area, and be able to sex a mature octopus. Local fishermen and divers that night dive should be able to tell you if octopuses occur in your area. As far as sexing octopuses goes, mature males will have a ligula, which looks something like a small catchers mit on one of their arms.

There are a number of ways to collect octopuses. One of the easiest and most fun is to go tidepooling during low tide at night. Night snorkelling, night diving, and laying trap lines of pots (artificial dens) may also work. Keep in mind that octopuses have an arsenal of tricks at their disposal. They can change colour, change skin texture, move through very small holes, produce an ink decoy, and jet. After you have collected an octopus, keep an eye on her or him and be prepared to do a water change if the octopus inks in a small volume of water. Also keep in mind that octopuses are notorious escape artists. If you plan to collect an octopus and are not familiar with their special needs, see Johnston and Forsythe (1993a, 1993b) and Wood (1994) for general information on octopus care.

Let's assume that you have a female octopus that lays fertile eggs in your tank. One of the marvellous aspects about octopus eggs is that they are clear and you will be able to observe the development of the baby octopuses. The time it takes for the eggs to hatch depends on the species and the temperature of the water. O. briareus eggs hatch in 50-80 days at temperatures between 19 and 25°C (Boyle 1983). By hatching time the eyes, gills, ink sac, chromatophores, etc. can all be seen. At about 3/4 of the time it take to hatch, the baby octopus will flip in the egg so that they are away from the stalked end of the egg. By this point you had better be ready for the what, when, where, and how's of collecting food for your baby octopuses.

Do not use Artemia as a food! The first food I tried was newly hatched Artemia as well as adult Artemia enriched with Selco and I lost all of the octopuses in that batch. Yes, O. briareus has a great feeding response and will capture Artemia but no one has documented positive growth using this food (Boletzky 1983). Foods that do work are: mysid shrimp, amphipods, crustacean larvae, crustacean appendages, little kids (just joking), and small crabs. Hanlon (1985) reports that food should be from 1/3 to 2 times the mantle length.

Baby octopuses are ravenous little beasts and are able to double their weight every week under the right conditions. For this reason, you will need to have a lot more food then you might think. Freshly killed food such as crustacean appendages will not move around so you will need to uses tweezers and bump the food into the octopuses yourself. Frozen food also will not work though it can be fed to adults. You should find that the little bugers eat a lot and grow fast. Octopuses need to grow fast to obtain their adult size in their short one to two year life span.

You should also know that octopus eggs can be artificially reared. Simply :-) remove some of the eggs from the mother (she has eight arms, you have two), transfer them to another tank, and suspend them in the water column. Use an airstone to provide a gentle current to keep the eggs well oxygenated and to prevent fouling. One reason that you might want to do this is so you can raise some of the eggs at a higher temperature. These eggs will hatch sooner and therefore give you an opportunity to work out some of the glitches (like "I didn't know that they would go up the airline tubing!" or "I didn't realize they eat THAT MUCH!") before the main batch hatches.

Octopuses can be either batch-reared or reared in individual containers. You will probably have a higher success rate if you individually rear them but this takes more room. O. briareus is one of the more cannibalistic species (Hanlon, 1985) so I would rear this species in individual containers. In any case be sure to provides some cover (pvc pipe, rocks, small shells, etc) for the little guys to hide in.

With a little preparation, luck, knowledge, and more than understanding loved ones, you can raise octopuses in your home. Just think, you could train a whole army of them to wash your dishes or steal documents from high security FBI crime labs.

References

Boletzky S. v. and R. T. Hanlon. 1983. A review of the laboratory maintenance, rearing and culture of cephalopod molluscs. Mem Natl Mus Victoria. vol 44:147-187.
Boyle, P. R. Ed. 1983. Cephalopod Life Cycles. Academic Press, London.
Johnston, L. and J. Forsythe. 1993a. An octopus in your house - part I. Aquarium Fish. vol 5, no 11.
Johnston, L. and J. Forsythe. 1993b. An octopus in your house - part II. Aquarium Fish. vol 5, no 12.
Hanlon R. T. and J. W. Forsythe. 1985. Advances in the laboratory culture of octopuses for biomedical research. Lab Anim Sci. 35:33-40
Sweeney, M. J., C. F. E. Roper, K. M. Mangold, M. R. Clarke, and S. v. Boletzky. 1992. "Larval" and juvenile Cephalopods: a manual for their identification. Smithsonian Institution Press, Washington D.C.
Wood, J. B. 1994. Don't fear the raptor. Freshwater and Marine Aquarium. vol 17, no 4

Articles Reference

Wood, J. B. 1995 Raising and Rearing Octopus briareus The Journal of Maquaculture (The Breeder's Registry). vol 3, no 2. Reprinted in: The Cephalopod Page. Wood, J. B. Ed.

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