Sealworm ( Pseudoterranova decipiens) infections in demersal fish from two areas in Norway

• Published in: Canadian Journal of Zoology
• Main Authors: Jensen, Tor, Andersen, Karin, Clers, Sophie des
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1994
• Subjects: Norway; Gadus morhua; Nordland; Phoca vitulina; Vega
• Online Access: http://dx.doi.org/10.1139/z94-082; http://www.nrcresearchpress.com/doi/pdf/10.1139/z94-082

Fish from Torbjørnskjær, in the outer Oslofjord in southern Norway, and from Vega in Nordland in central Norway were examined for infections of the larval nematode Pseudoterranova decipiens transmitted by seals. Three sites were sampled between 1990 and 1992, two (S1 and S2) in Torbjørnskjær and one (S3) in Vega, and 3361 fish were examined in total. In Torbjørnskjær, fish were collected from shallow waters (S1) near skerries where a colony of common seals (Phoca vitulina) regularly haul out, and from deeper waters outside these skerries (S2). In Vega, an extensive zone of rocks and shallow water is inhabited by a colony of grey seals (Halichoerus grypus) and some common seals. In Vega, fish were caught from the littoral zone to 40–50 m depth, except for cusk (Brosme brosme), which were caught in deeper waters. Only demersal and benthic fish were infected in both areas, infection levels being highest in shallow waters close to the rocks (sites S1 and S3). Sculpins (Myoxocephalus scorpius) had the highest infection levels (an average abundance of 36 and 23 worms per fish, respectively), with cod (Gadus morhua) and cusk also heavily infected; the latter species was found only at Vega. Two somewhat different transmission routes to seals are suggested for the two areas.