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  • From abalone to oysters, pearls to seaweed, foodfish to baitfish, aquaculture provides us with a bounty of goods. Some people are turning to aquaculture with hope as natural stocks decline, and although it may not be the panacea, it is the fastest growing sector of U.S. agriculture. Aquaculture now supplies about 10% of the seafood that Americans consume, with 60% coming from imports and 30% coming from wild catch. A decline in wild catch and pressure to reduce seafood imports are helping to stimulate growth in U.S. aquaculture production.

    Aquaculture is defined as the farming of aquatic organisms, which include plants and animals, freshwater and marine. Like other methods of farming, it is labor-intensive and occasionally subject to Mother Nature's whims. We have acquired much knowledge of nutritional requirements, controlling reproduction, managing water quality, system design, and factors influencing growth (e.g. water temperature, stocking densities, pond size, diseases). However, knowledge should not be mistaken for complete control. We can't control the weather, and we can't possibly keep our systems at optimal operating conditions constantly. There are also quite a few challenges for the aquaculture industry to overcome in order to mitigate its impact on the environment. Coastal habitat destruction, waste discharge, and the escape of farm-raised animals are all concerns which need to be addressed.

    The practice of pond culture existed centuries ago in almost every ancient culture; the Egyptians raised fish, the Greeks and Romans raised eels, the Chinese grew carp, the Japanese cultured pearls, and the Europeans farmed oysters. Today, pond culture is still practiced, and evolving technologies have allowed for the creation of some high-tech culture systems, such as indoor, recirculating systems.

    The farming of marine organisms is called mariculture. Shellfish culture takes place along coastlines, and fish can be raised in cages or net pens in enclosed bodies of water like bays. Some are experimenting with extremely large open ocean cages, engineered to withstand extreme conditions. Mariculture has lagged behind freshwater aquaculture because the successful spawning and larval rearing of marine fish are more complex. It is more difficult to satisfy the food requirements of larval marine fish; live foods such as zooplankton must be offered instead of pelleted foods. Advances are being made, however, with many marine species, such as cod, halibut, turbot, sea bass, tuna, mahi-mahi, and flounder. Shellfish have a readily available food source in the wild since they are filter feeders, and many shellfish are successfully cultured, including oysters, clams, scallops, and mussels. Techniques for the production of marine shrimp are also well established, as are those for salmon, an anadromous fish which spends most of its life in the ocean.

    The Canadian Ministry of Fisheries and Oceans provides aquaculture production statistics for the years 1986-1998. Using the following species, graph total production over the 13 years for each one: salmon, trout, steelhead, clams, oysters, mussels, and scallops. For which species do you see steadily increasing production? (Before looking at your graphs, make a guess based on the farmed product you see most often in the grocery store and that you think is the most popular among consumers.) Do the same exercise using data representing private aquaculture production in the United States for the years 1985-1997 with the following species: salmon, trout, catfish, clams, oysters, mussels, and crawfish. For which species do you see steadily increasing production? Which is the only species whose production has increased steadily in both Canada and the U.S.? Compare quantities produced. (In fact, world production of this species has increased steadily. The U.S. imports it, and Canada is one of its main suppliers.)

    Notes: (1) You will want to convert the Canadian and U.S. figures to a common unit of measure for comparison (1 metric ton = 2205 pounds). (2) When working with the figures for salmon in the Canadian data set, you will need to add several species together (Atlantic, chinook, and coho) for the first few years.

    The global demand for fisheries products will continue to increase as the world population continues to expand. Many wild stocks are either approaching their biological limits or are already overfished, so it is clear that aquaculture will have to play an increasingly important role in the future.

    If you are interested in setting up your own aquaculture project in your classroom, visit the web site of the National Council on Agricultural Education. You will find information on instructional materials, how-to manuals and teacher training, a discussion list, and links to schools with aquaculture programs. You can also get ideas from the Aquaculture in Action web site. To get your students even more excited, you may want to consider entering a Secondary School Aquaculture Competition.

    For more resources, be sure to check out AquaNIC, Aquaculture and Aquatic Science Education Links from the Delaware Aquaculture Resource Center, and the Bridge's Aquaculture page. If you have questions about the Data Tip of the Month or have suggestions for a future data tip, contact Lisa Lawrence, Bridge Data Project Manager.

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