17 - Parasites in farmed fish and fishery products

Abstract

Parasitism is a highly successful way of life as it has evolved independently in almost every phylum of protists, animals and plants. However, the degree to which parasites might affect their hosts is highly variable, ranging from an apparently uncomplicated co-existence with low virulence to situations where they might strongly affect entire host populations, under both natural or aquaculture conditions. In many parasite groups, but especially among aquatic ones, there are intricate and complex life cycles. These generally involve one or more intermediate hosts where larval development or asexual multiplication occurs and a definitive host in which to breed and from which to shed their offspring in order to ensure dispersal. Besides the species of concern to seafood safety, other frequently occurring parasites affect the food quality as they might severely reduce the aesthetic appearance of the product. Thus, a number of different fish parasites might have severe economic impact, either related to their pathogenicity, often resulting in substantial losses under aquaculture conditions, or due to their importance regarding the quality and safety of fish and fishery products. The continuously growing awareness by consumers and public food authorities as to the possible presence of parasites or parasite-related quality defects in seafood emphasizes the importance of providing the fish processing industry with up-to-date knowledge on the occurrence, detection, and control regarding the most important parasite species of fish.