DOMOIC ACID IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) FEEDS

Contamination of fish feeds with the toxin, domoic acid, through use o f contaminated fish meal is a possibility. To test the stability of do moic acid during fish meal and fish feed manufacturing, fish meal was made from anchovies containing 43 mu g domoic acid/g wet fish using a closed vacuum dryer, resulting in fish meal containing 130 mu g domoic acid/g of meal. This product was used in place of commercial herring meal in a dry, pelleted feed, constituting 50% of the feed formulation . The feed contained 58 mu g domoic acid/g. To determine if dietary do moic acid affected the health of rainbow trout or was retained in the tissue, duplicate groups of trout, average initial weight 25 g, were f ed a control diet, made with herring meal, and the domoic acid diet fo r 15 weeks, during which time the average weight of the trout increase d to 48 g. No differences in feed consumption, weight gain, or feed ef ficiency ratio were observed between groups of fish fed the control or domoic acid feed. No mortality or signs of toxicity or neurological d istress were observed in either dietary treatment group. Analysis of f ish tissue showed no detectable concentrations of domoic acid in fille ts or viscera portions of the fish when the fish were sampled after a 48-h fast. Domoic acid was present in the feces and viscera, but not i n blood or muscle of the fish following an overnight fast. These resul ts suggest that domoic acid in fish feed, when present at a concentrat ion likely to be encountered in practical situations, is not readily a bsorbed by rainbow trout and does not present a health hazard to the f ish or to the consumer.