San Francisco — One of California's newest farms has no farmyard, fields, or cows -- and it's 15 feet underwater. The experimental sea farm, built by marine biologists in San Francisco Bay, has only one crop -- seaweed covered with fish eggs. But if all goes well, that crop will be worth up to $20,000 a ton, and the farm may help preserve a fishing industry threatened by disappearing seaweed.
Dr. Judith Hansen, a marine biologist at the University of California, Santa Cruz, started the pilot farm in an effort to preserve the Bay Area's valuable kazunoko kombu fishery.
Kazunoko kombu -- a coveted Asian delicacy consisting of herring eggs on seaweed -- is created each winter when millions of fertile herring swim under the Golden Gate Bridge and into the bay to spawn. While herring lay their eggs on almost any surface, many will coat seaweed called kelp with layers of small, rubbery eggs. Within hours, the egg-frosted kelp is harvested, then pickled in brine.
Much of the crop is exported to Japan, where it is viewed as a delicacy. Dr. Hansen says, ``It's a type of caviar,'' selling for $8 to $20 a pound; the kelp serves as a cracker.
Although several tons of kazunoko kombu are harvested each year, this has little effect on future herring populations, Hansen says, because the eggs that are collected are likely to die anyway. Kazunoko kombu harvesters prefer kelp with 10 or more egg layers, and most of the eggs inside such thick masses die before they hatch.
While the herring aren't threatened, however, the kelp is. In the last decade, the ``cracker'' has begun to disappear from California's coastal waters, jeopardizing the kazunoko kombu industry. Although reasons for the kelp decline are not well understood, researchers say that natural cycles, pollution, changing weather patterns, and overharvesting of the state's natural kelp ``forests'' all may contribute to the losses.
Concerned about the decline, state fish and game officials asked Hansen to study ways to cultivate a kelp called Laminaria sinclarii. Particularly prized by kazunoko kombu harvesters, this kelp is scarce in the herring spawning grounds. Eventually, Hansen's research may lead to commercial kazunoko kombu farms, along with domestic seaweed ``nurseries'' that could restock wild populations. Already, officials in Canada and the state of Washington have expressed interest in Hansen's work, which was funded by the California Sea Grant program, a part of the National Oceanographic and Atmospheric Administration.
Learning to grow Laminaria in the laboratory was a key step toward establishing the farm, and for this Hansen collaborated with a visiting Chinese seaweed expert, Dr. X. G. Fei, head of seaweed mariculture (farming) research at the Institute of Oceanology in Qinsdao, China. The Chinese are the world's leading seaweed farmers, and few American researchers match their experience. In part, that is because wild seaweed stocks are plentiful here, easily meeting the relatively small demand for seaweed. Until recently, there has been little motivation to set up controlled seaweed farms in the United States.
Drawing on decades of Chinese experience, however, Dr. Fei saved Hansen months of work by helping her discover the correct lighting, temperature, and nutrient conditions that make wild kelp reproduce ``on demand'' in laboratory tanks.
It takes three months for the kelp at the farm to become ready for herring eggs and harvest. The process starts several months before ``planting,'' when Hansen and her assistants collect sexually mature wild kelp. Then, in small laboratory tanks, the kelp is coaxed into producing microscopic reproductive spores, which settle on thin nylon strings and begin to grow. After a month in a ``nursery'' at Santa Cruz's Marine Laboratory, the young kelp look like a brown fuzz and are ready to be put in the ocean. Once in the ocean, the kelp grow quickly to foot-long blades.
The location of the farm is important. Tidal currents, for example, must be strong enough to deter other seaweed from growing on the kelp. These ``epiphytes'' foul the crop. And under California Fish and Game Department regulations, which govern all sea farming ventures, the farm can't hinder fishermen or block boating routes.
Most important, however, the farm must be near the herring spawning grounds. Hansen says the fish missed an earlier farm because it wasn't near traditional spawning areas. This year she put the farm where the fish routinely lay their eggs.
Still, success isn't guaranteed. ``They may spawn someplace one year but not come back the next,'' says Jerry Spratt, a marine biologist with the Fish and Game Department.
In an effort to learn more about herring spawning habits, one of Hansen's colleagues, Dr. Michael Moser, seeks to discover whether herring hatched at the farm will return to their birthplace as spawning adults.
If they do, future kazunoko kombu farmers would be assured of a crop every year, and Hansen's research could spawn an important Bay Area industry.