Challenges and realistic opportunities in the use of by-products from processing of fish and shellfish

•Industrial processing of fish and shellfish may result in as much 70% of by-products.•Much focus is on converting this potential waste into commercial products.•The most realistic uses of such by-products are as food or feed ingredients.•Isolation of high-value products is in most cases commercially unrealistic.

By-products may constitute as much as 70% of fish and shellfish after industrial processing and much focus has been on converting these into commercial products. The aim of this paper is therefore to evaluate important challenges and to consider the most realistic options in the use of by-products. Certain by-products like heads, frames and off-cuts from filleting of fish may be used directly as food while by-products in general can be transformed into feed ingredients e.g. for the expanding aquaculture industry. Although sometimes suggested, it is unlikely that by-products can be used to any large extent to produce high-priced products.