As the aquaculture industry moves toward more sustainable feed solutions , the use of low-trophic marine organisms such as mussels and tunicates is gaining momentum. Their favorable protein and fatty acid profiles make them attractive alternatives to conventional feed ingredients like fish meal and fish oil1. However, filter feeders such as mussels and tunicates are known to bioaccumulate algal toxins during harmful algal blooms. Algal t oxins, such as okadaic acid/dinophysistoxins (OA/DTXs) and saxitoxins (STX, NEO, GTXs, and C-toxins) can persist in the tissues of mussels2 and , if incorporated into fish feed, could pose potential risks to both fish health and food safety , if transferred.
This study evaluates the potential impact and transfer of selected algal toxins in salmon feed through a controlled, stepwise feeding trial using Atlantic salmon ( Salmo salar) parr and post-smolt. Diets were formulated using commercial ingredients and top-coated with purified OA/DTXs in ethanol, or saxitoxins in water. Fish were fed until they doubled in weight. All diets were well accepted, maintaining comparable growth performance and feed efficiency to their respective water- or ethanol-based controls. However , microarray analysis revealed altered gene expression in the mid intestine of fish exposed to okadaic acid toxin group. Preliminary LC-HRMS/MS analysis of parr tissue samples did not indicate any detectable transfer of two saxitoxins (STX and NEO) to the fillet. Analysis for the remaining saxitoxins and for three OA/DTXs is under way.
This study contributes to the ongoing risk assessment of novel, underutilized low-trophic marine feed ingredients, supporting the goal of sustainable, Norwegian-sourced aquafeeds. Understanding the fate and impact of algal toxins in fish feed is essential for ensuring fish welfare, consumer safety, and responsible feed innovation.
References:
Miljøstiftelsen Bellona. (2022). “Hva Skal Laksen Spise? – Råvareløftets Veikart Og Barrierestudier for Nye Fôrråvarer [What should the Salmon eat ? The roadmap and barrier studies of the raw materials initiative for new feed ingredients].”
James KJ, Carey B, O’Haloran J, Van Pelt Fnam , Škrabakova Z. Shellfish toxicity: human health implications of marine algal toxins. Epidemiology and Infection . 2010;138(7):927-940.