Fish processing plants convert fresh or frozen fish into various types of product. Processing plants can be labour intensive and or highly automated. They are used to process single or multi-species on low or large volumes depending on the capacity of the facility and availability of raw material. Both capture fisheries and aquaculture provide fish that is factory processed. Factory processing produces a variety of different products such as chilled, frozen, smoked, dried and surimi.    

Typical operations inside a factory include stunning, grading, slime removal, de-heading, washing, scaling, gutting, cutting of fins, filleting, de-boning, meat bone separation, packaging and labelling. Waste is often generated during some of these operations. This waste is sometimes classed as by-products or co-products.  

Fish processing facilities generate a significant amount of fish by-products (co-products) that could be an important source of energy, food, fertilizer or industrial feedstock.

The discards from the processing plants can be used to produce fish protein concentrate, fish oils and enzymes (such as pepsin and chymotrypsin), and other value-added products. The fish oil is used for products such as margarine, omega-3 fatty acids and biodiesel. The fish protein concentrate is used as human food and animal feed. Fish protein is also rich in amino acids which are highly suitable for human consumption.