Fish byproducts have commercial possibilities.

Alaska's fish-processing industry produces more than 2.2 billion pounds of fish byproducts every year--the equivalent, in weight, of nearly 10,000 blue whales. Large processors often convert these byproducts into fishmeal or fish oil, which are generally sold for little profit. There is little economic incentive for smaller processors to do the same, so they generally return byproducts to the ocean, where they are consumed by marine creatures.

But these processors may be throwing money into the sea. Global demand for fish protein will exceed supply by 2016, according to the Juneau (Alaska) Economic Development Council. USDA-ARS scientists are finding that fish byproducts have marketable potential. Take fish livers, for example. They aren't a very popular menu item in the United States. Kids rarely clamor for fish liver snacks, and few people include them in their regular diet.

But they have potential as a dietary supplement. Livers from different species of fish all show positive nutritional properties to varying degrees. Not all cold-water marine oils are created equal. And, oils from different marine species have different amounts of omega-3 fatty acids.

Cold-water marine fish tend to have higher omega-3 content than many warm-water marine fish, which tend to have more omega-3 than freshwater fish. With omega-3 fatty acid levels of 20% or more, Pollock and salmon rank at the top. In one study, the scientists compared livers from seven fish species harvested in Alaska--walleye Pollock, pink salmon, big-mouth sculpin, Pacific halibut, arrow-tooth flounder, flat-head sole and spiney-head rockfish--and examined their composition in terms of proteins and oils.

The liver proteins of all the fish had high levels of essential amino acids. Liver lipid content--a strong indicator of omega-3--ranged from 3.3% for pink salmon to 50.3% for walleye Pollock. Investigators concluded that differences between species could enable development of unique ingredients for food or animal feed, allowing producers to target products to specific markets. Fish oil and protein supplements for humans can be made from high-fat livers. And low-fat livers, such as salmon, can be used as supplements for pets and livestock as well as humans.

Studies conducted by ARS researchers and scientists from the University of Alaska confirmed that protein powders made from cold-water marine byproducts could be used as feed ingredients for aquaculture or livestock. And the fish-based proteins compare favorably to products already used in food, dietary supplements, medical treatments and animal feed.

Further information. Peter Bechtel, USDA-ARS Subarctic Agricultural Research Unit, 245 O'Neill Building, University of Alaska, Fairbanks, AK 99775; phone: 907-474-2708; fax: 907-474-7204; email: bechtel@sfos.uaf.edu.