Flounder skin meal as a potential protein source substitute in the diet of juvenile black rockfish (Sebastes schlegeli)

In this study, we investigated the potential utility of fish skin, usually discarded during processing, as a cost-effective protein source. We evaluated the effects on juvenile black rockfish (Sebastes schlegeli) of an 8-week feeding trial in which 0%, 5%, 10% or 20% of the casein (purified protein) in their diets was replaced with flounder skin meal. The fish that received flounder skin meal, particularly the 20% group, showed significantly higher growth performance and feeding efficiency. They had lower levels of body lipids, elevated levels of high-density lipoprotein cholesterol, and increased body and muscle protein contents. They recovered more rapidly from stress induced by anaesthesia or exposure to air. Supplementation with flounder skin meal confirms the functionality of flounder skin meal as a high collagen component of fish diets.