Occurrence and distribution of anisakid nematodes in Grey gurnard (Eutrigla gurnardus L.) from the North Sea

Grey gurnard (Eutrigla gurnardus L.) is an abundant and widely distributed demersal fish in the North Sea. It is currently considered a sustainable stock, thus permitting future increased utilisation as a food resource. In order to address both consumer safety and aesthetical product quality, the occurrence and distribution of anisakid nematode larvae in Grey gurnard from two localities in the North Sea were investigated. Two anisakid species were recorded, i.e. Hysterothylacium aduncum in the viscera, and Anisakis simplex in both the viscera and flesh of the fish. Virtually all gurnards were infected with nematode larvae. However, H. aduncum was significantly less abundant than A. simplex in the fish from both localities. Only for the gurnards from the northernmost sampling locality there was a significantly positive correlation between host body weight and total A. simplex abundance. No such correlation was found for H. aduncum in either locality. Separate analyses of the Anisakis infection data in gurnards of marketable size (≥250 g) and pooled for both localities, revealed 83% prevalence of A. simplex larvae in the fish flesh, ranging 1-16 in intensity. The relative larval distribution between the viscera and flesh was 89 and 11%, respectively. Moreover, a significantly positive correlation was found between A. simplex occurring in the viscera and the flesh of this particular host size group, i.e. the number of larvae in the flesh appeared to increase with increasing infection level in the viscera. In general, Grey gurnard from the North Sea can be considered as heavily infected with nematode larvae. Especially the comparatively high abundance of A. simplex larvae in the flesh is of concern regarding the possible intensified utilization of Grey gurnard as a food resource.