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Did You Know?

Background Agricultural Connections

Aquaculture is the production of aquatic organisms under controlled conditions throughout part or all of their lifecycle.¹ It is the farming of aquatic organisms using interventions such as seeding, stocking, feeding, protection from predators, etc.² Seeding refers to the use of fish eggs, larvae, or hatchlings to establish new populations. Stocking is the practice of raising fish in hatcheries and releasing them into bodies of water to increase the fish population.

The United States Department of Agriculture (USDA) categorizes aquaculture products as food fish, mollusks, crustaceans, ornamental fish, sport fish, bait fish, and miscellaneous. Food fish and mollusks are the largest product categories. Catfish, clams, crawfish, oysters, saltwater shrimp, and trout are the top aquaculture products raised in the United States.

Catfish: Catfish are the largest aquaculture industry in the United States.³ Worldwide, there are more than 2,000 species of catfish. Channel catfish and Blue catfish are the most commonly raised and consumed species in the United States.

Catfish are slender with a flat underside and forked tail. They do not have scales or incisors (cutting teeth). They feed through suction or gulping. Catfish are fed pellets that contain soybean meal, corn, rice, and fish meal. The pellets float on the surface of the water.

U.S. farm-raised catfish are grown in freshwater, clay-based ponds that are environmentally controlled. Mississippi produces over 50% of U.S.-grown catfish. Together, Alabama, Arkansas, Louisiana, and Mississippi produce 94% of the farm-raised catfish in the United States.³ 

Mature breeding catfish produce 3,000-4,000 eggs a year and remain in production for 4-6 years. The fertilized eggs are taken to hatcheries where they hatch after seven days. They are then moved into special ponds where they grow into fingerlings (the size of an index finger). When the fingerlings are 4-6 inches long, they are moved to a new pond where they grow for about 2 years. 

The catfish are harvested when they are about 1.7 pounds each. Seines (large, weighted nets) are used to harvest the catfish which are transferred to aerated tank trucks to be transported to processing plants. After harvesting, the catfish are cleaned, processed, and frozen to a temperature of -40°F. The catfish can be sold as whole fish, steaks, filets, strips, and nuggets, marinated and breaded, or precooked in frozen dinners.

Catfish are low in calories and a good source of lean protein, healthy fats, and essential nutrients including B vitamins, omega-3, and omega-6. Eating catfish can benefit heart, brain, eye, and bone health.

Catfish can be consumed fried, grilled, steamed, poached, or smoked, or added to soups, stews, or curries,

Clams: Hard clams, also known as quahogs are the most common species of clams farmed in the United States. Clam farming is considered one of the most eco-friendly forms of aquaculture because it does not require feed, antibiotics, or fertilizers. As filter feeders, clams help improve water quality by filtering out plankton, nutrients, and other particles from the water. Clam beds create habitats for various marine species, which contributes to biodiversity in coastal ecosystems. 

Virginia, Washington, Florida, and Maine are the top states for farm-raised clam production. Clam larvae are bred in hatcheries and fed algae for about three weeks until they develop shells and lose their ability to swim. They are then moved to a nursery where they are kept in upwellers (systems where water is continuously circulated, bringing plankton to the clams to eat) for several months until they are ready to be moved to the farm site. Clam farms are typically located in shallow coastal waters or estuaries. The juvenile clams are raised on the sea floor in anchored mesh bags, cages, or nets for 12-36 months. They filter feed plankton that occur naturally in the water.

Clams are harvested when they reach 1.5-3 inches in shell length. Specialized rakes, dredges, or hand-harvesting methods are used to collect the clams. After harvesting, the clams are cleaned, sorted, and packaged to be transported to markets, restaurants, or processing facilities. 

Clams are high in protein and omega-3 fatty acids and low in fat and calories. They are a good source of vitamin B12, vitamin C, iron, zinc, magnesium, selenium, and potassium. Clams support cardiovascular health, boost the immune system, and improve blood health.

Clams are sold live, fresh, frozen, or canned and are popular in chowders, stews, and pasta.

Crawfish: Crawfish, also known as crayfish and crawdads, are freshwater crustaceans. There are over 600 species of crawfish worldwide. One of the most well-known species, the red swamp crawfish, are native to the southeastern United States and are widely farmed for food. White river crawfish are another commonly farmed species.

Louisiana leads the nation in crawfish production. Smaller harvests of farmed crawfish are produced in Texas, Arkansas, Mississippi, Alabama, California, North Carolina, and South Carolina. Crawfish grow best in shallow ponds (1-2 feet deep) in areas with clay or loamy soils and vegetation such as rice or native grasses that provide food for the crawfish. New ponds are filled with water and stocked with juvenile crawfish in April or May and drained in May or June to encourage the crawfish to burrow into the soil. Crawfish feed on organic matter found in the ponds such as decaying plants, plankton, and small aquatic organisms. If supplemental feeding is necessary, farmers will add formulated feeds to support growth.

Crawfish are ready to be harvested in the spring. Baited traps are left in the ponds overnight and retrieved the next day. This process is repeated regularly throughout the spring and summer while the crawfish continue to grow and reproduce.

Crawfish are low in fat and calories and high in protein and nutrients like vitamin B12, iron, phosphorus, zinc, magnesium, and selenium. They contain omega-3 fatty acids that help reduce inflammation, lower blood pressure, and improve overall heart health. Crawfish support bone and dental health, boost the immune system, promote nerve and muscle function, and help with weight management.

Crawfish are an essential part of Cajun and Creole cuisine. They are used in crawfish boils, étouffée, bisques, stir-fries, and gumbo. Peeled crawfish tails can be added to salads, pastas, po'boys, and pizza.

Oysters: Oysters are a type of mollusk and popular shellfish, valued for their unique flavor and texture. There are five primary species of oysters consumed worldwide—Pacific oysters, Atlantic or Eastern oysters, European flat oysters, Kumamoto oysters, and Olympia oysters. The Atlantic (Eastern) and Pacific oysters are the most popular species produced in the United States. The Atlantic (Eastern) oyster is found primarily in the Gulf Coast and Chesapeake Bay regions and makes up about 75% of the total U.S. harvest. Virginia, Washington, Louisiana, California, Massachusetts, Alabama, and Oregon are the top oyster-producing states.

Oysters are bred in a hatchery. The eggs develop into free-swimming larvae that feed on microscopic algae provided by the hatchery. After 2-3 weeks, after developing a tiny shell, they are placed in mesh bags, cages, or tanks with a substrate (shells from other oysters or synthetic materials) known as a cultch and feed on plankton in the water. As the oysters grow larger, they are transferred to estuaries, bays, or shallow coastal waters where they are either grown directly on the seafloor (bottom culture) or in suspended systems like floating cages, racks, or baskets. They consume plankton and other nutrients naturally found in the water and do not require external feeding.

Once the oysters reach market size (within 18-36 months), they are harvested at low tide using techniques like hand harvesting, raking, using tongs, or dredging. After harvesting, the oysters are cleaned, sorted by size, and prepared for market distribution.

Oysters are high in protein and low in calories. They are a good source of zinc, iron, magnesium, calcium, phosphorus, and selenium. Oysters are rich in B vitamins, especially vitamin B12, and provide omega-3 fatty acids.

Oysters are eaten raw or cooked. They can be grilled, roasted, fried, steamed, poached, smoked, baked, or canned. Oysters can be served as appetizers, in seafood platters or ceviche, or used in po'boy sandwiches, stews, and soups.

Saltwater Shrimp: Saltwater shrimp, also known as marine shrimp, are species of shrimp that thrive in the ocean or other saltwater environments. The most common saltwater shrimp produced in the United States are white, pink, and brown shrimp. Texas is the largest producer of farmed saltwater shrimp in the United States, followed by Florida, Hawaii, and Alabama.

Saltwater shrimp are bred in hatcheries. The larvae grow in a controlled environment until they are large enough to be moved to coastal ponds, tanks, or net pens in the sea. The shrimp are raised in saltwater or brackish water (a mix of fresh and saltwater) and are fed commercial pellets.

After 3-6 months, the shrimp reach market size and are harvested by draining ponds or using nets. After harvesting, the shrimp are transported by truck or boat to facilities where they are sorted, washed, packed, and chilled.

Shrimp are low in saturated fat and high in protein. They are a good source of phosphorus and vitamin B12. Shrimp promote heart and brain health, strengthen bones, and help maintain weight loss.

Shrimp can be boiled, grilled, fried, sautéed, steamed, or served as an appetizer or in ceviche, tacos, skewers, scampi, stir-fries, or sandwiches.

Trout: Trout are carnivorous freshwater fish known for their colorful patterns, delicate flavor, and strong swimming ability. The rainbow trout is the most commonly grown trout species in the United States. They are easy to raise, have fast growth rates, and tolerate crowding well. Brook trout and brown trout are also raised in the U.S., but to a lesser extent. Idaho is the top producer of trout in the United States, producing about 70% of the nation's domestic trout. North Carolina, Washington, California, and Pennsylvania also produce trout.

Trout are bred in hatcheries. Once the eggs hatch and the young fish (alevins) absorb their yolk sacs, they are transferred from incubators to nursery tanks where they are fed special diets to promote growth. As they grow, the fry are moved to larger tanks or ponds and are now called fingerlings. At this stage, they require higher protein feeds to support rapid growth. The juvenile trout are then moved to freshwater systems like ponds, tanks, raceways (narrow, long tanks), or net pens in lakes and reservoirs where they are fed high-protein pellets.

When the trout reach market size (1-3 pounds), they are harvested by draining the raceways or ponds and collecting the fish with nets, pumps, or vacuum systems. Before harvesting, they are fasted for 24-48 hours to reduce the amount of waste in the system and to empty their digestive tracts which ensures the fish are clean and easier to process. After harvesting, the trout are sorted, processed, and packed for sale.

Trout are high in protein, low in calories and fat, and rich in omega-3 fatty acids. They are an excellent source of vitamin B12, vitamin D, and other B vitamins like niacin (B3), riboflavin (B2), and B6. Trout also contain selenium, phosphorus, and potassium. Eating trout can reduce inflammation and support heart, brain, and cognitive health.

Trout can be grilled, pan-fried, sautéed, baked, smoked, canned, or poached and can be used in soups, stews, sushi, tacos, burgers, and salads.

Engage

Explore and Explain

Activity 1: Aquaculture Food Products

1. Divide the class into six groups. Allow each group to pick one Aquaculture Information Card out of a hat or box.
   • Catfish Information Card
   • Clam Information Card
   • Crawfish Information Card
   • Oyster Information Card
   • Saltwater Shrimp Information Card
   • Trout Information Card
2. Provide each student with a Become an Aquaculture Expert activity sheet and Aquaculture Flowchart.
3. Explain to the groups that they will become experts for the aquaculture product on their card. Instruct them to read the information, watch the video (links on the cards and below), and search for information online to complete their activity sheet.
   • Catfish
   • Clams
   • Crawfish
   • Oysters
   • Saltwater Shrimp
   • Trout
4. Provide each group with a folder, and instruct them to label the folder with the name of the aquaculture product they were assigned and the names of everyone in their group. Direct them to place their Aquaculture Information Card, Aquaculture Flowchart, and completed Become an Aquaculture Expert activity sheet in their folder. Explain that they will add additional information to the folder and then use it at the end of the lesson to create a mock field trip adventure to share the information they found during their research with others.

Activity 2: Nutritional Benefits of Aquaculture Products

1. Reorganize the class back into their groups from Activity 1 and provide each group with the Nutrition Facts and Health Benefits handout for their aquaculture product (links below). Hand out the Aquaculture Nutrition Comparison Chart to each student.
   • Catfish Nutrition Facts and Health Benefits
   • Clam Nutrition Facts and Health Benefits
   • Crawfish Nutrition Facts and Health Benefits
   • Oyster Nutrition Facts and Health Benefits
   • Saltwater Shrimp Nutrition Facts and Health Benefits
   • Trout Nutrition Facts and Health Benefits
2. Using the information from their Nutrition Facts and Health Benefits handout, each group should fill in the information for their aquaculture product on their Aquaculture Nutrition Comparison activity sheet.
3. Bring the students back together as a class and project the activity sheet onto a large screen. Explain to the class that they are going to compare the nutritional facts of the six different aquaculture products the groups have been researching. Have a representative from each group share the nutritional information for their aquaculture product while the students complete their activity sheets.
4. After all the information has been recorded, lead a discussion comparing the nutritional value of the six aquaculture products. Use the following questions to guide the discussion:
   • Which aquaculture product contains the most calories? Which contains the least?
   • Which aquaculture product contains the most total fat? Which contains the least?
   • Which aquaculture product contains the most protein? Which contains the least?
   • Which aquaculture product contains the most carbohydrates? Which contains the least? 
   • Which aquaculture product contains the most fiber? Which contains the least?
   • What do the aquaculture products have in common?
5. Have the groups place their handouts and activity sheets into their group folders.

Activity 3: Mock Field Trip Adventure

1. Explain to the class that they will be working with their group to create a mock field trip adventure. Their group will take on the roles of farmers and create a field trip experience for an elementary school class that is visiting their farm. The experience should include visuals (ex., models or posters of their aquaculture product being raised) and the opportunity to share the following information:
   • Name of the aquaculture product
   • How the product is raised 
   • How the product is harvested
   • How the product is consumed
   • Nutritional value and health benefits of the product
2. Provide the materials and time necessary for the groups to create their visuals.
3. Allow time for the groups to practice their field trip presentations.
4. Invite other classes to attend the field trip presentations.

This lesson investigates a variety of aquaculture products, where they are grown and raised, and their nutritional benefits. If you live in the following states, refer to your local agricultural literacy resources about aquaculture: Alabama Catfish Georgia Fish Louisiana Crawfish Marine Fisheries Oysters Maine Mississippi North Carolina Oysters Oklahoma Fish

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