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Home , Sea cucumber

Scientific Excellence • Resource Protection & Conservation • Benefits for Canadians 5

DFO li llil~~i[1i11~1i1l11i11~iiii1lieque 02021242

no.54 1989 c.2 2 Underwater World

ea (Parastichopus ca/ifor­ Distribution and Habitat Snicus) are flexible, cylindrical-bodied cucumbers are found throughout Sea creatures which move sluggishly over the the nearshore waters of British Columbia floor, using their feeding tenta­ from extreme low tide to depths of more cles to pick up food. These marine inver­ than 90 m. They only avoid areas tebrates are known as , exposed to high wave action, and are which means "spiny-skinned", and are found on all types of bottom, from close relatives of the and sea muddy sand to bedrock. star (Fig. 1). The inside of their body walls have five muscle strips running Reproduction and Growth from the front to the back. At the front Spawning occurs mostly from June to end of the , the mouth is ringed August and is accomplished by shedding by feeding . and eggs into the water where fer­ One of the novel features of sea tilization takes place. During this shed­ cucumbers is that many stop feeding in ding, sea cucumbers adopt a "cobra­ October or November and, when exam­ like" posture, with the front end ined, are found to contain no internal elevated off the bottom. The fertilized organs. Until recently, it was thought eggs develop into larvae which may that they spontaneously expelled these spend 70 days as suspended in body parts, but in fact, they simply the water before settling on the bottom "atrophy" or waste away. New internal and changing into miniature, juvenile organs are regenerated in about six sea cucumbers. Juveniles are very secre­ weeks. Why such organ losses occur is tive and hide among sea weed, under another mystery surrounding these stones, and in crevices. Growth is interesting creatures. thought to be slow, requiring at least As they crawl about, their light four to five years for adult size of 0.5 kg amber-coloured ventral surface is in to be reached. Their life span may be contact with the sea bottom. This ven­ more than eight years. tral surface bears many small tube­ shaped projections tipped with suckers Feeding Habits and Predators called "tube feet". The dorsal surface Sea cucumbers browse slowly over the is covered with stiff, conical projections bottom, feeding on microorganisms and can vary greatly in colour from light associated with sediment particles. Fig. 1. Sea cucumber (Parasticho­ red to dark burgundy or even mottled Then, like earthworms, they pass out p us californicus) brown. Sea cucumbers may reach 45 cm strings of undigestible material such as (Photo: N.A. Sloan) in length and weigh more than 1 kg. sand grains and shell fragments. Adult sea cucumbers have few known predators, with the exception of three species of sea stars. These predators can induce a violent arching back-and-forth escape response in sea cucumbers, which is the only time they move rapidly! Juveniles are probably more vulnerable and this may explain their secretive behaviour.

Fishery Landings of sea cucumbers have been recorded from southern British Colum­ bia since 1980 and are given in metric tons in Table 1. Harvesting (Fig. 2) occurs in less than 18 m by divers, who gather them into large mesh bags which are periodically hauled to the surface vessel. The east coast of Vancouver Island, south from Johnstone Strait through the Strait of Georgia to Victoria, accounts for almost all the Underwater World 3

12.ndings (Fig. 3). The west coast of Vancouver Island is lightly fished, while the coast north of Vancouver Island remains unfished. Processors pay up to $0.15 each for sea cucumbers from which the main product is the five muscle strips from the inside surface of the body wall. Domestic and export markets are still developing, a situation which is partially responsible for the fluctuating landings. The muscle strips are delicious when quickly fried in butter, and the domes­ tic market is expected to grow as more Canadians become acquainted with this delicacy. Elsewhere in the world the main product of sea cucumber is the whole gutted, dried body wall, called "trepang", which is used to make soup in . Thi. roduct is also available in many North American Asian communities. However, the body wall of our local species may be too thin for drying into prime quality "trepang".

Fig. 2. Fishermen sorting their Management sea cucumber catch Fisheries management has been care­ (Photo: B.E. Adkins) ful to control fishing until the biology of local stocks is more thoroughly Table 1. Landings of sea cucumbers. understood. Much of the coast has been Year 1980 1981 1982 1983 1984 closed to fishing for sea cucumbers, and Land ings( !) 20 27 4.5 527 95 is now being opened gradually as more Fig. 3. Sea cucumber fishing diving fishermen become interested in areas of British Columbia the resource. Fishermen must provide log records of their fishing activity to assist managers in acquiring more data on the abundance and distribution of the species. Fishermen are now required BRITISH to have a special licence for their vessels COLUMBIA to fish for sea cucumbers. The can easily be collected by recreational divers and in British Columbia, there is at present no recreational catch limit.

PACIFIC

OCEAN

- MAJOR LANDINGS

r owl MINOR LANDINGS 4 Underwater World

Further Reading: Text: Cameron, J .L. and P .V. Fankboner. N.A. Sloan 1984. structure and feeding Department of Fisheries and processes in life stages of the commer­ cial sea cucumber Parastichopus Fisheries Research Branch calijornicus (Stimpson). J. Exp. Mar. Pacific Biological Station Biol. Ecol., 81: 193-209. Nanaimo, British Columbia V9R 5K6 Harbo, R. 1982. Diving Fishermen. Diver, (June) 20-23. Underwater World factsheets are brief illustrated accounts of fisheries re­ McDaniel, N., 1982 . The giant sea sources and marine phenomena pre­ cucumber. Diver, (March) 26-27. pared for public information and edu­ cation. They describe the life history, McNair, D., 1982. Fish of the month: geographic distribution, utilization and Sea cucumbers. Pacific Fishing, 3 population status of fish, shellfish and (September): 47-52. other li vi ng marine resources, and/ or the nature, origin and impact of marine Sloan, N .A., 1985 . fisher­ processes and phenomena. ies of the world: A review. In: Proceedings of the Fifth International Echinoderm Conference, Galway, Ireland. Edited by B.F. Keegan, A.A. Balkema, Rotterdam. Pages 109-124.

Sloan, N.A., 1986. World Jellyfish and Tunicate Fisheries, and the Northeast Pacific Echinoderm . Cana­ dian Special Publication of Fisheries and Aquatic Sciences, No. 92 (in press).

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