Scallops as a saltwater crop. With expertise from Japan, Canada tries to set up hatcheries
Nanaimo, British Columbia — THE sex life of scallops isn't likely to make the front pages of the supermarket tabloids. But researchers in Nanaimo hope greater knowledge of the reproduction of these sea creatures will create a new industry for British Columbia. ``Our project is to investigate the feasibility of scallop culture in British Columbia,'' says Neil Bourne, a research scientist at the Pacific Biological Station here.
The province has two hatcheries growing oysters by artificial cultivation and more than 50 ``farms'' raising salmon in pens in the ocean.
Scallops - a shellfish that many recognize because of the corporate symbol used by the Shell Oil Company - would make a third aquacultural source of jobs and income for the province.
Some 13 species of scallops live naturally in the rich waters off British Columbia. Four of these are large enough or available in sufficient numbers to harvest. But last year only 71 metric tons were taken from the ocean bottom - a tiny amount compared with the more than 100,000 tons harvested wild from Georges Bank off the East Coast or the 200,000 tons taken from a few Japanese bays each year.
The Japanese yield is so high because they help nature along. Mr. Bourne wants to do the same - introducing the handsome Japanese scallop to British Columbia waters.
``We are developing hatchery techniques to produce large quantities of juveniles for grow-out operations,'' he says.
Scallops are, to say the least, fecund. A single animal can produce 100 million to 150 million eggs, each about 80 microns across. The trick is to enable enough of these to survive as free-swimming larvae and get them settled on a surface as ``spat'' - tiny shellfish.
In Japan, in Mutsu Bay, Funka Bay, and off Hokkaido, the scallops spawn naturally in late February and March. These start settling as spat in April and May. The members of Japanese fishing cooperatives set out ``spat bags'' in the ocean to provide more surfaces for the larvae to attach themselves to. These bags contain bunches of old gill netting, cedar boughs, or other materials. Once the spat have reached fingernail size, feeding on the microscopic plants in the water, they would normally fall to the bottom of the ocean to grow ``wild.'' Instead they fall to the bottom of the small-mesh bag - perhaps 100 to 1,000 per bag.
Then the Japanese either drill a hole through the ``ear'' of the scallop shells and hang them on ropes in the water to continue feeding until they reach commercial size, or they dump them overboard in areas of the bays that have been cleared of their natural enemy, the starfish. The scallops are harvested when they are about four inches across.
Only the ``adductor'' muscles that open and close the shells are eaten as a seafood delicacy in North America. The Japanese, in contrast, eat pretty well everything.
Conditions in British Columbia are not suitable for exactly the same process, in part because scallops do not reproduce naturally in such a large population as they do in the Japanese bays. So Bourne and his assistants, after importing a brood stock of Japanese scallops in 1983, have been developing methods to get them to spawn in a hatchery and then raise them to young juveniles.
When examination shows a few scallops are ``ripe'' for spawning, they are taken out of the water for an hour or so, then put back in somewhat warmer water. In about half an hour, the males emit their sperm into the water and half an hour later the females their eggs - perhaps 25 million of them. These solutions are mixed and the fertilized eggs are put into an eight-foot diameter tank of sea water. The resulting larvae - perhaps a few million of them - are strained out of the water with a screen and put into another tank where they are fed daily with phytoplankton. Three species of these tiny sea plants are raised in separate tanks for this purpose.
``You make or break it on the food,'' says Bourne.
After some 28 days, the larger larvae are separated out and put into ``settling'' tanks where they fasten themselves as ``spat'' to Kinran, an inexpensive artificial fibrous material.
In 1987, in some 11 spawns at the laboratory here, the scallops produced around 145 million eggs, of which perhaps 60 million survived as ``straight hinge'' larvae. Some 17.3 million of these settled as spat, or just about 12 percent of the original eggs.
That survival rate is sufficient to be economic, says Bourne. The final result might be 25,000 juveniles that could be raised to maturity for the dinner table.
``We certainly feel we can produce commercial-size scallops in two years,'' Bourne says. ``We have to do it or the economics aren't there. We have to improve the techniques so we are a little more efficient.''
Bourne hopes to launch a joint pilot project with an oyster grower in 1988 or 1989. The juvenile scallops would be set in the ocean by ear-hanging or in nets for growing to maturity. ``We have excellent growing conditions here,'' he says.
Nonetheless, it could be five years before Bourne knows if his work will produce a commercial result. ``I am very optimistic,'' he says.