Marine By-Products Tested as Feed for Almaco Jack Seriola rivoliana and Their Effect on Fatty Acids and Sterols in Different Tissues

Marine by-products can compose up to 70% of the total weight of products from fisheries, most of which are discarded. However, these by-products are rich in highly unsaturated fatty acids that are not synthetized by most marine animals produced by aquaculture. Here, we used three marine by-products (shrimp head, Catarina scallop viscera, and Pen shell viscera) to produce lipid-rich (72.9–144.6 g/kg) meals which were used to partially substitute commercial fishmeal (FM) on feeds that were used to grow Almaco Jack ( Seriola rivoliana ) juveniles for 10 weeks. The content of 20:5n-3 and 22:6n-3 in tissues of fish fed shrimp and Pen shell presented values similar to controls, but the former had a better effect on growth, lipid, and phytosterols levels. Catarina meal had lower concentration of 20:4n-6 and 22:6n-3 in feed but promoted higher proportion of 20:4n-6 in muscle and 22:6n-3 in liver, indicating a selective conservation in relation to other fatty acids. Catarina meal contained traces of 18:5n-3 (0.02 g/kg) indicating that scallops probably ingested dinoflagellates; after testing, phycotoxins like okadaic acid (OA) and dinophysistoxin 1 (DTX1) were detected by mouse bioassay, by lateral flow immunochromatography, and quantified by HPLC–MS/MS. The presence of these toxins at the detected concentrations (OA: 27.64 µg/g and DTX1: 10.31 µg/g) affected almaco jack juveniles, a setback that needs to be addressed before meal manufacturing from mollusks. Marine by-products rich in lipids can be used to reduce the use of FM in the diet, and their use improve the lipid content and growth compared to control diet with FM. Graphical Abstract