Hälsostatus hos abborre (Perca fluviatilis) i Gumpfjärden, Bottenhavet
Perch (Perca fluviatilis) is a very popular fish in Sweden and it is common in Swedish waters. In some areas along the Swedish coast the perch population has decreased. It is therefore important to get a view at the health status of perch. During April, July and August of 2008, a total of 346 perches were caught in the Gump Bay in the Botnian Sea. The fish were mainly caught by net but also by rod. They were examined for external and internal changes and virological, bacteriological, parasitological and histological studies were performed. No pathogenic viruses or bacteria known to affect fish were found. Parasites were common. However, they did rarely exist in any large numbers. Externally, two species of parasites were found; Argulus foliaceus and Piscicola geometra. On the gills Trichodina spp. were very common but Achteres percarum and parasites from the family Epistylididae were also found. Five different species were identified from the gastrointestinal tract; Acantocephalus spp, Proteocephalus spp., Camallanus sp., Contracaecum sp. and Schistocephalus spp. The most common pathological change seen in this study was cysts in the liver. From the cysts Triaenophorus nodulosus and a nematode were identified. Sporocysts containing Glugea sp. were found in the intestinal villi. In the mesenterium numerous numbers of cysts and granuloma like changes were seen but the cause of these could not be determined. The overall health status of perch in the Gump Bay was considered good.