DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03391

Endoparasitic helminths in Baltic salmon Salmo salar: ecological implications

Agung Cahyo Setyawan, Shaozhi Zuo, Per W. Kania, Kurt Buchmann*

*Email: kub@sund.ku.dk

ABSTRACT: Presence of parasites in fish are ecological indicators as they reflect migration routes, feeding behavior and immune status of the host and thereby represent valuable biological information. We performed a parasitological investigation of sea-running Baltic salmon caught in the Southern Baltic Sea to investigate the use of parasites as indicators for this fish stock. The host is a strain of the Atlantic salmon Salmo salar, which for several millennia has been isolated in the semi-enclosed brackish Baltic Sea with limited out- and inward migration to and from the North Sea. A total of 24 salmon (total body weight ranging from 4.2 to 14.2 kg, total body length 80–105 cm) were caught by spoon-bait during their feeding migrations. Fish were necropsied few hours after capture and internal organs were subjected to a parasitological investigation focusing on endoparasitic helminths. The pyloric region was heavily parasitized by the cestode Eubothrium crassum (100% prevalence, intensity 97–273), reflecting a diet of smaller pelagic fishes. The stomach contained a high number of the hemiurid digeneans Brachyphallus crenatus (95.8% prevalence, intensity 8–151) and Hemiurus luehei (58.3% prevalence, intensity 2–13) indicating a diet which contains clupeids. Schistocephalus solidus, liberated from ingested sticklebacks, (25% prevalence, intensity 1–2), the acanthocephalan Echinorhynchus truttae (prevalence 54%, intensity 1–13) and the adult nematode Hysterothylacium aduncum (29%, intensity 1–13) were found in the intestine. The liver was parasitized by third stage nematode larvae of Contracaecum osculatum (45.8% prevalence, intensity 1–4) but these larvae were growth stunted and encapsulated. The parasite fauna differs markedly from the one in salmon in North Atlantic waters and the lack of purely marine parasite species indicates that the Baltic salmon has remained in the Baltic sea during its life-history.