Tag Archives: Fish Farming Cage systems

Sustainable feed resources

Fish farming is very efficient in terms of the conversion of protein, which means an important ecological advantage in light of the sustainability of fish feed resources.

One of the most-frequently cited issues with the sustainable development of aquaculture is the capture of other fish as raw material to be used as fish feed in the form of fish meal and fish oil. It is seen as an issue because a food production sector is in part relying on a capture fishery for the supply of raw materials for the production of aquaculture feed.

Typically, these other fish species are small, oil-rich, bony pelagic fish that are not normally used for direct human consumption. Two decades ago, the majority of fish meal and oil was used to make feeds for land animal production. At present, over 50 percent of fishmeal and over 80 percent of fish oil is used for aquaculture.

If aquaculture is to fill the gap in demand for seafood, this raises important sustainability issues as to the availability of sufficient feed supply. This is particularly relevant given the fact that fishmeal and fish oil production has been, and is likely to remain, relatively constant at around 6 million and 0.9 million tonnes per year, respectively.

However, as the demand for fishmeal and fish oil in aquaculture has increased, so the price has risen. This has driven both terrestrial agriculture and aquaculture to seek nutritional alternatives to fishmeal and fish oil. This is an on-going process and estimates made by the International Fishmeal & Fish oil Organisation (IFFO) show that the growth of aquaculture and the substitution of fishmeal and fish oil can continue together. The IFFO has started to produce datasheets on fisheries for fish meal and fish oil and these are available at the IFFO web site.

Conversion of caught wild fish to farmed fish

It has been noted that certain types of fish, particularly salmon, are net consumers, requiring in the region of 3 kg of wild fish as feed to produce 1 kg of farmed fish. While it is true that growing high-quality salmon requires considerable amounts of fishmeal and oil, improved technology in fishmeal and oil production as well as better feeding practices on farms have reduced the ratio over time.

Salmon are an exception, because their diets require large amounts of fish oil. For aquaculture overall, the ratio is now well below one: less fish is used for feed than is produced at farms. For carnivorous species, the ratio is still decreasing and expected to reach 1.0 around 2012 (IFFO).

These figures do not include recent gains thanks to the recovery of meal and oil from aquaculture waste. Increasingly in Europe, waste from aquaculture is collected and processed, redirecting around 50 percent of the harvested weight to valuable products.

It should also be noted that wild carnivorous fish also need food. It is estimated that it takes 10 kg of forage fish to produce 1 kg of salmon caught in the wild6. If by-catch values are added to the equation, another 5 kg of forage fish has to be added. Hence, even a 3 to 1 ratio for farmed salmon would be significantly better than a 10-15 to 1 ratio of salmon caught in the wild.

 Efficiency of food conversion in farmed fish

The ‘food conversion ratio’ (FCR) is defined as the weight of food that is required to produce one kilogram of fish. In the early days of aquaculture, farmed fish were fed with whole ‘trash’ fish and FCRs were more than 20 to 1. Through the years, the ratio has dramatically declined. With the advent of dry, pelletised feeds and modern extrusion technologies, FCR levels are now almost 1 to 1. Certain trout and salmon farms achieve an FCR of less than 1:1, making them far more efficient converters of marine protein than their wild counterparts.

As fish feeds represent an increasingly high share of total production cost, fish farmers have every interest in using feeds as effectively as possible, thereby also reducing the potential environmental impacts of non-consumed feeds. Overfeeding or underfeeding would increase the FCR. Therefore, many farms are equipped with underwater surveillance and monitoring systems as well as devices controlling the supply and delivery of feed.

Replacement of marine protein sources by (terrestrial) plant protein

For various reasons, fishmeal and oil are gradually being replaced by plant proteins in feed that is used in fish farms. Plant proteins can be less costly and they are free of potential contaminants like dioxin, PCB or mercury.

However, fishmeal is an important ingredient in fish feed and can only to a limited extent be replaced by vegetable proteins without reducing feed efficiency and growth. After all, carnivorous or ‘piscivorous’ fish naturally feed on other fish. The fatty acid composition in the flesh from farmed fish will also reflect the feed composition and inclusion of vegetable oil will reduce the level of omega-3 fatty acids.

Although the introduction of plant protein into the feed can be seen as a way of reducing the sector’s dependence on fish meal and fish oil, some have questioned the trend because:

  • carnivorous fish do not naturally feed on plants;
  • plant proteins may have anti-nutritional effects on fish;
  • there is a maximum level of replacement, after which the texture and eating quality
  • of the fish is compromised;
  • some plant proteins could be derived from GMOs.

Generally speaking, though, marine plants have enormous potential to act as fish feed ingredients. Initial research has confirmed this potential and our knowledge in this area is starting to build.

Decontamination of fish meal and fish oil
Fishmeal and fish oil are produced from fish that may contain contaminants. Various research projects are ongoing to look into the feasibility of de-contaminating fish meal and fish oil. One such project is carried out at the Fiskeriforskning Institute in Norway.

Fish stocks of concern in the northern European industry are sprat and herring from the Baltic Sea, and herring, sprat, sand eel and blue whiting in the North Sea. The differences in dioxin and PCB levels reflect the general pollution levels in the respective fishing areas and will disfavour the North European fishmeal and oil producers in the world market. This is already the case in aquaculture, where most fishmeal is sourced from the southern hemisphere.

The main objective of the project is to develop a new oil extraction process to reduce the persistent organic pollutants level in fishmeal. The research will aim to identity optimal processing conditions with respect to both decontamination efficiency and preservation of fishmeal and oil quality. The new oil extraction process is expected to have several advantages compared to a standard hexane extraction process. This will include the possibility of easy integration in an existing fishmeal processing line, use of a safe and non-flammable extraction medium and lower investment and operation costs.

Do farmed fish contain artificial colouring?

The natural red/orange colour of salmon results from carotenoid pigments, largely astaxanthin in the flesh. Astaxanthin is a potent antioxidant that stimulates the development of healthy fish nervous systems and that enhances the fish’s fertility and growth rate. Wild salmon get these carotenoids from feeding on small crustaceans, such as prawns and shrimp. Astaxanthin does not naturally occur in fish feeds and thus must be added. The astaxanthin which is added to feed is identical to the natural pigment.

Food miles

In recent years, there has been increasing emphasis on energy resources needed to ship in food from afar. Although the relationship between transport and overall sustainability can be complex, it can be said that where food supply chains are otherwise identical, reducing food transport improves sustainability.

Therefore, generally speaking, European aquaculture production could be seen as more efficient in terms of “food miles” than imports of the same species from countries far away.

However, there is a food mile issue with the use of fish meal and fish oil produced in the southern hemisphere and used in Europe, although this is itself a trade-off of not using fish meal produced in Europe due to issues of species in recovery (e.g. sandeel and capelin) and contamination of fish meal and oil (e.g. Baltic herring).

However, as stated before, comparisons can be complex, involving differences between food supply systems that often involve trade-offs between a diverse variety of environmental, social and economic factors. The impact of food transport can be offset to some extent if food imported to an area has been produced more sustainably than the food available locally. For example, a case study showed that it can be more sustainable (at least in energy efficiency terms) to import tomatoes from Spain than to produce them in heated greenhouses in the UK outside the summer months.

In the case of fishmeal and fish oil, the world’s largest producers of fishmeal and fish oil are in South America. There, fishmeal and fish oil are mass-produced very efficiently and shipped overseas (already with a reduced water content in the case of fishmeal) to Europe to be used as feed in aquaculture. Surely, this has to compare favourably to using airplanes to import fresh fish from Asia or South America.

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Should You Attempt Fish Farming?


Considerations for Prospective Fish Growers

Louis A. Helfrich, Fisheries Extension Specialist, and George S. Libey, Associate Professer, Aquaculture; Department of Fisheries and Wildlife Sciences, Virginia Tech


Fish farming is an ancient practice that can provide many profitable opportunities today. The raising and selling of fish on a commercial basis has proven to be economically successful throughout the United States. In Croatia, fish farming is growing in popularity. Increasing recognition that fish is a healthy food, low in calories and cholesterol levels, but rich in protein has increased consumer demand in both restaurants and supermarkets.
Fish are excellent animals to rear. They can convert feed into body tissue more efficiently than most farm animals, transforming about 70 percent of their feed into flesh. Fish also have excellent dress-out qualities, providing an average of 60 percent body weight as marketable product and a greater proportion of edible, lean tissue than most livestock. Fish can be intensively cultured in relatively small amounts of water. In Virginia, they can be farmed at densities near 2,000 pounds/acre with careful management. Farm-reared fish offer a new alternative agricultural crop that can potentially replace those which are declining in popularity or profitability. Healthy farm-reared fish, guaranteed free of diseases, pesticides, and other harmful toxicants, are a more desirable substitute for wild fish from potentially polluted waters.

Fish farming is, like most other types of farming, a risky business that requires special knowledge, skills, and careful considerations. Some of the most important factors to consider in determining whether you should begin a fish farming business are listed below. Answering yes to all or most questions does not insure success. Similarly, answering no to all or most questions does not guarantee failure. Individuals with little or no experience in fish farming and few resources available can become successful fish farmers, but they should start small and expand slowly, and be willing to invest lots of time and effort.

Answer Yes or No

Do you have sufficient financial resources available?
2. Do you own suitable land with a good source of high-quality water?
3. Do you own enough land and water necessary for a profitable venture?
4. Is there a high demand and sufficient market for your product?
5. Do you have the equipment and machinery necessary?
6. Is expected profit from fish farming greater than other land uses?
7. Can you really devote the money, time, and labor necessary?
8. Do you know the costs involved with the following items:

Capital CostsLand & buildings
Building ponds/raceways
Trucks & tractors
Plumbing & pipes
Tanks & aerators
Oxygen meters
Nets & boots
Operating CostsPurchasing eggs/fingerlings
Fish feed
Electricity & fuel
Labor & maintenance
Chemicals & drugs
Taxes & insurance
Telephone & transportation

Is there an established market for your fish?
2. Is the market demand sufficient year-round?
3. Do you have an alternative marketing strategy to rely on?

Do you have a continuous source of clean, high-quality water?
2. Does your soil have enough clay content to hold water?
3. Is the water temperature optimal for the fish species reared?
4. Do you have space sufficient to build enough ponds or raceways?
5. Do you have good and easy pond access for feeding and harvesting?
6. Are the pipes sufficient in size for quick draining & easy filling?
7. Is your residence near enough for direct observation and security?
Have you had your water tested (chemical and bacteriological)?
2. Do you have a reliable source of fingerlings or eggs at affordable prices?
3. Do you have a reliable source of feed at reasonable cost?
4. Do you have dependable labor available at affordable wages?
5. How long is your growing season (days/year)?
6. What’s your production capacity (pounds/year)?
7. What’s the best fish species for you to grow?
8. Are you aware of fish reproductive biology and nutritional needs?

Are you aware of the federal and state laws about fish farming?
2. Do you know where to apply for the necessary permits and licenses?
3. Are you familiar with the personal liability concerns involved?

Risk Assessment:
Can you afford to lose your entire fish crop?
2. Can you conduct water quality tests?
3. Is fish-disease diagnostic-help readily available?
4. Do you know about off-flavor and its causes?
5. Is pesticide, metal,or oil contamination possible?
6. Can you deal with poachers and vandals?
7. Do you know where to go for information and help?

Fish Farming Publications

Magazines/ Newsletters
Aquaculture Digest
9434 Kearney Mesa Rd.
San Diego, CA 92126

Aquaculture Magazine
P.O. Box 2329
Asheville, NC 28802

Aquafarm Letter
3400 Neyrey Drive
Metairie, LA 70002
Arkansas Aquafarming
University of Arkansas
Cooperative Extension Service
Box 391
Little Rock, AR 72203

California Aquaculture
University of California
Cooperative Extension Service
Aquaculture Extension
Davis, CA 95616
Canadian Aquaculture
4652 William Head Rd.
Victoria, British Columbia
Canada, V8X3W9

Carolina Aquaculture News
P.O. Box 1294
Garner, NC 27529

Farm Pond Harvest
Professional Sportsman Pub.Co.
Box AA
Momence, Illinois 60954

Fish Farmer
Business Press International
205 E. 42nd St.
New York, NY 10017

Fish Farming International
Heighway House
87 Blackfriars Road
London SE 1814B England

Fish Farming International
110 Fleet St.
London EC4A England

For Fish Farmers
Mississippi State University
Cooperative Extension Service
Mississippi State, MS 39762
Georgia Fish Farmer
University of Georgia
Cooperative Extension Service
Athens, GA 30602

Salmonid Magazine
U.S. Trout Farming Asso.
506 Ferry St.
Little Rock, AR 72203

South Carolina Aquaculturist
Clemson University
Cooperative Extension Service
Room 102, Long Hall
Clemson, SC 29631

Texas Aquaculture
Texas A&M University
Cooperative Extension Service
102 Nagle Hall
College Station, TX 77843

The Catfish Journal
Catfish Farmers of America
P.O. Box 1700
Clinton, MS 39056

Timely Tips-Fisheries
University of Tennessee
Cooperative Extension Service
P.O. Box 1071
Knoxville, TN 37901-1071

Water Farming Journal
3400 Neyrey Drive
Metairie, LA 70002

World Aquaculture News
P.O. Box 150129
Arlington, TX 76015
Journals/ Technical Publications
American Elsevier Scientific Pub. Co.
52 Vanderbilt Ave.
New York, NY 10017
32 issues/yr.–$640/yr.

Aquaculture Engineering
Elsevier Applied Science
52 Vanderbilt Avenue
New York, NY 10017

Journal of Shellfish Research
National Shellfisheries Association
Oyster Biology Section
Gulf Coast Research Lab.
Ocean Springs, MS 39564

Journal of the World Aquaculture Society
178 Pleasant Hill
Louisiana State University
Baton Rouge, LA 70803

Progressive Fish Culturist
American Fisheries Society
5410 Grosvenor Lane, Suite 110
Bethesda, MD 20814-2199

Transactions of the American Fisheries Society
American Fisheries Society
5410 Grosvenor Lane, Suite 110
Bethesda, MD 20814

Selected Fish Farming Books

  • A Guide to Integrated Warm Water Aquaculture. D. Little and J. Muir. Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, Scotland.
  • Aquaculture Engineering. 1977. F.E. Wheaton. R.E. Krieger Publishing Company, Kreiger Dr., Malabar, FL 32950.
  • Aquaculture: The farming and husbandry of freshwater and marine organisms. 1972. John Wiley & Sons, Inc. New York, NY.
  • Cage Aquaculture. 1987. M. Beveridge. Unipub, 4611-F Assembly Drive, Landham, MD 20706-4391. Phone (301) 459-7666. ($38)
  • Commercial Catfish Farming. 1973. Interstate Printers and Publishers. Danville, Il.
  • Crustacean and Mollusk Aquaculture in the United States. J.V. Huner and E.E. Brown. AVI Publishing Co., Inc., 250 Post Road East, P.O. Box 831, Westport, CT 06881.
  • Fish Farming Handbook. 1980. AVI Publishing Co., Inc., Westport, Ct. 06881.
  • Fish Hatchery Management. 1986. American Fisheries Society, 5410 Grosvenor Lane, Suite 110, Bethesda, MD 20814.
  • Guidelines for Striped Bass Culture. 1976. American Fisheries Society, 5410 Grosvenor Lane, Suite 110, Bethesda, MD 20814-2199.
  • Principles and Practices of Pond Aquaculture. 1986. American Fisheries Society, 5410 Grosvenor Lane, Suite 110, Bethesda, MD 20814-2199, Phone (301) 897-8616. ($39.95)
  • Principles of Warmwater Aquaculture. 1979. John Wiley & Sons, Inc. New York, NY.
  • Principles of Warmwater Aquaculture. 1979. American Fisheries Society, 5410 Grosvenor Lane, Suite 110, Bethesda, MD 20814-2199. Phone (301) 897-8616 ($39.95)
  • Recent Advances in Aquaculture. J. Muir and R. Roberts. Westview Press Inc., 5500 Central Ave., Boulder, CO 80301.
  • The Aquaculture of Striped Bass. 1984. Maryland Sea Grant Program, 1224 Patterson Hall, Univ. of Maryland, College Park, MD 20742.
  • Trout and Salmon Culture (Hatchery Methods). 1980. California Fish Bulletin Number 164. University of California, Berkeley, CA 94720.
  • Trout Farming Handbook. 1973. Scholtum International Inc. Flushing, NY.
  • Water Quality in Warmwater Fish Ponds. 1984. C.E. Boyd. Auburn University, Auburn, AL 36830. ($8)


American Fisheries Society
5410 Grosvenor Lane
Suite 110
Bethesda, MD 20814-2199

Catfish Farmers of America
P.O. Box 36
Jackson, MS 39205
National Ornamental Goldfish Growers Asso.
6916 Blacks Mill Rd.
Thurmont, MD 21788

National Shellfisheries Association
Edwin Thodes
National Marine Fisheries Service
212 Rogers Ave.
Milford CT 06460

Shellfish Institute of North America
National Fisheries Institute
2000 M Street, NW, Suite 580
Washington, DC 20036

U.S. Trout Farmers Association
515 Rock Street
Little Rock, AR 72202

World Aquaculture Society
341 Pleasant Hall
Baton Rouge, LA 70803

CCRES AQUAPONICS special thanks to Michelle Davis, Research Associate, Fisheries and Wildlife

Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.

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