The Future is Abundant
A Guide to Sustainable Agriculture

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Water Culture

Mike Maki

The abundance of life surrounding a body of water, even a small pond or marsh, helps one understand water's productive potential and longstanding importance for human civilizations. With the depletion of common fishing grounds, many people are now turning toward raising fish and wetland plants in private ponds and other improved aquatic systems. Good opportunities exist for increased production through introduction of especially productive varieties and polyculture of aquatic organisms.

The best overall strategy for establishing a self-sustaining aquaculture is to maintain and enhance native fisheries and, where necessary, to rehabilitate degraded watersheds. Many streams and rivers which were once home to salmon, trout and steelhead are now blocked by dams, stripped of streambank vegetation, and choked with sediment by poor logging and farming practices. As a result, salmon, trout and steelhead fisheries have declined sharply in recent years. In response to this situation, stream rehabilitation projects are now underway throughout the region.

Pond Culture

Ponds and other water storage structures can be of great value in restoring natural conditions by retaining water in the surrounding soil and by providing a supply of irrigation water for plants used in watershed rehabilitation. Building ponds also results in increased wildlife diversity.

Algae, plankton, and tiny crustaceans are the basic foods for fish and other higher forms of pond life. For algae-feeding fish species, occasional fertilization of the pond with animal manure or similar high-nitrogen food will induce growth of plankton and algae, but abrupt population surges of these tiny organisms may cause nutrient competition and oxygen depletion. For this reason, population and oxygen levels should be closely monitored. Good monitoring equipment is essential for intensive aquaculture.

Aquatic polyculture has been carried on for centuries in various parts of the world. In northern Europe, ducks, fish, and crayfish are raised toghether in freshwater ponds. The ducks eat the algae and small fish, and deposit manure which promotes further growth of algae and aquatic plants. Crayfish, considered a delicacy by Europeans, eat these plants, as do other herbivorous fish. These are in turn eaten by predatory fish such as bass. People then harvest the fish, ducks, and crayfish for food. This type of polyculture is a managed imitation of natural ecosystems.

Aquaculturists generally recommend stocking ponds with native species whenever possible. The ecological implications should always be considered when non-native species are introduced. Carp, for example, are non-native, bottom-feeding vegetarian fish which can survive in many of the region's warmer waters. They flourish in irrigation canals in California, and several species are used in polyculture in Asia, Europe and Africa. However, their feeding activity stirs up sediment, ruining the habitat for trout and other native fish. So despite its potential aquacultural value, the introduction of carp for commercial purposes is banned in most parts of the United States.

The common Pacific Northwest crayfish (Pacifasticus leniusculus) is an edible crustacean which flourishes in slowly moving water. Crayfish eat a wide variety of foods, from fish wastes to pond weeds. Crayfish are planted in California and Louisiana in flooded rice fields for insect and weed control and harvested after the fields are drained. Our native species is now being planted widely in Europe, to replace the native European crayfish which were wiped out by a fungal epidemic.

Among freshwater fish, trout seems to have the greatest potential in the Northwest. Trout farming is already a big industry in the region, with over 90% of the rainbow trout in the U.S. produced in the Magic Valley of southern Idaho. Active programs for superior stock selection have been underway for over 50 years, and much information is available on trout biology and ecology.

The use of home-produced feeds for pond fish has been extensively and successfully experimented with, using ingredients such as low-grade beef and beef liver, wheat, fish meal, whey, bran, and greens. Earthworms are an excellent fish food. They can be grown near the pond and fed whole to the fish, or mixed into a balanced blend.

for the small pond manager, a good feeding strategy is to allow fish to search the pond themselves for most of their food, providing supplemental feedings once or twice a day. In a large-scale pond culture, the best approach may be to release limited numbers of desired species, such as crayfish, trout, catfish, bullfrogs or ducks, and allow time for natural population dynamics to establish a balance.

Aquatic Plants

Freshwater shorelines are productive natural areas which support many useful plants and animals. Cattail (Typhus latifolia) is one wetland plant with a variety of uses. Wild food gatherers know the delicious taste of its young shoots and pollen heads. Researchers in Minnesota and New York are investigating cattails for their potential as human and animal food, and as a source of biomass energy. Starchy cattail storage roots, or rhizomes, can yield up to 30 dry tons per acre. They contain more protein on a dry weight basis than corn or rice, and more fat and minerals than corn, rice or wheat. Even if the roots are intensively harvested, there are usually enough small rhizomes left in the ground to reseed a stand.

Another useful freshwater plant is duckweed (Lemnaceae). These tiny floating plants act as bio-filters by feeding on algae and organic waste. Duckweed is a favorite food of wild ducks (hence its name), but recent experiments show the potential value of harvesting and feeding this quick-growing, high protein crop to domestic animals.

Although most algae have only recently been considered valuable by humans, an exception is the spirulina algae (Spirulina plantensis), which has been gathered for food and fertilizer in some parts of the world for centuries. Three areas which are particularly rich in this high protein freshwater organism are Lake Chad in Africa, Lake Texcoco in Mexico, and Upper Klamath Lake in southern Oregon. Large scale harvesting of algae from Upper Klamath Lake, originally begun to control pollution, now provides valuable animal feed and fertilizer. Deliberate culture of freshwater algae is still largely experimental in this country, but the practice is growing quickly in Japan and other parts of the world.

Mariculture

The intertidal zone is particularly rich and in many parts of the world it is extensively harvested for human food. At times this coastal zone is flooded by ocean tides, and at other times it is dry and exposed to direct sunlight. This ecological edge is well populated by many species of algae, sea vegetables and shellfish.

In the Northwest, harvesting of intertidal life for personal consumption is permitted in many places, including many public-access beaches. Harvest limits and regulatory agencies have been established to protect these areas from depletion. Of the native shellfish, one of the most abundant and least utilized is the blue mussel (Mytilus edulis). In many parts of the world these mussels are harvested both from the wild and from domestic plantings. They are just now gaining well-deserved acceptance in the Northwest as a delicious sea food.

From late spring to autumn, a toxic algae bloom called red tide occasionally makes shellfish poisonous to humans. Red tide is caused by small red algae, Gonyaulax catenella, which grow in huge colonies under certain conditions. The shellfish themselves are unharmed by red tide, and in fact flourish on the tiny algae. Commercially grown oysters, mussels and other filter-feeding shellfish are best harvested in winter, after the danger from red tide has passed.

Seaweed

Many seaweed species thrive in the cool waters of the Pacific Coast. Most need rocks or other solid structures to which they can attach themselves. In Scotland, coastal villagers once put stones on sandy intertidal bottomlands to act as seaweed holdfasts. The stones were placed in rows so wagons could pass between them, making for easy harvesting at low tide. In Japan, sophisticated techniques for seaweed culture have evolved over the centuries.

Many people in the Northwest are beginning to include seaweeds in their diet. Evelyn McConnaughey has collected much useful information about eating seaweed in her book, Sea Vegetable Recipes from the Oregon Coast. She says:

       There are hundreds of species of marine algae (seaweeds)
     here, many of which are similar or identical to those
     used for centuries as an important and highly prized part
     of the diets of other sea coast people.  Lest you reject
     eating seaweeds if all you've seen are those washed up,
     decaying and swarming with beach hoppers, consider the
     difference between fresh garden vegetables and those
     consigned to a compost heap some days ago.  Observing
     seaweeds exposed on rocky shores at low tide one can
     begin to imagine their beauty, variety and color under
     water, supported by the nourishing ocean.

Another important use of seaweed has been for fertilizer. The carbohydrates in these aquatic plants break down readily in the soil and promote the growth of soil microorganisms. They are also a rich source of minerals. On the Aran Islands of the northern Scotland coast, where the soil is little more than bare rock, potatoes are grown using a heavy mulch of seaweed and sand. This is called the "lazy bed" method. Many coastal people in the Pacific Northwest also gather seaweed and eelgrass for winter garden mulch and fertilizer.

Raft Culture

Using rafts and floating pens for raising fish and shellfish can be highly productive. The first use of nets for "growing" marine shellfish in Europe is attributed to a shipwrecked Irish sailor who suspended a net between two poles to catch sea birds. Later he discovered that mussels had attaced themselves to the net when it was submerged at high tide. Nori, a seaweed of the Porphyra genus, is grown on suspended nets in the shallow waters of coastal Japan and can be combined with raft culture of fish and mussels.

Many varieties of nori grow naturally in Puget Sound, but development of raft culture is just beginning. San Juan Sea Farms on Lopez Island is currently establishing both rope culture for mussels and nets for nori production. A Pacific Northwest Nori Growers' Association has also formed to develop what could become a major new industry in the region.

The Future is Abundant A Guide to Sustainable Agriculture