Katarzyna Stańczak

Gyrodactylus proterorhini Ergens, 1967 (Monogenoidea, Gyrodactylidae) in gobiids from the Vistula River—the first record of the parasite in Poland

During a parasitological survey of two non-native fish species—racer goby Neogobius gymnotrachelus and monkey goby Neogobius fluviatilis—in the Włocławek Reservoir on the lower Vistula River, the monogenean Gyrodactylus proterorhini was recorded for the first time in Poland, and for the first time, the racer goby was listed as the parasite host. Specimens of G. proterorhini were detected on body surface, fins, and gills of the fish studied. In 2006, the monkey goby was infected with the prevalence 41%, racer goby with the prevalence of 47%, at maximal intensity of 6 and 9 parasites per fish, (respectively). The infection level in relation to the fish size and sampling season was also discussed. The presented study supports the hypothesis of progressive introduction of the parasite with gobiids to the colonized areas.

Ovarian alterations in wild northern pike Esox lucius females.

The aim of the present study was to analyse the occurrence of macroscopically visible ovary alterations in 2 populations of northern pike Esox lucius L. originating from lakes in the Mazurian Lake District (NE Poland). The alterations were characterised by ovary tissue that was morphologically malformed, in part or in whole, and contained immature oocytes, i.e. trophoplastic or previtellogenic oocytes instead of vitellogenic oocytes. These alterations were found only in the ovaries, and no morphological alterations of the testes were noted. Macroscopic and histological analyses were carried out in order to classify the observed alterations in the ovaries. Three types of alterations were identified in which morphological malformations as well as histological investigation of the ovaries were considered. An analysis of the size and age of the fish in relation to the occurrence of alterations as well as of the macroscopic and histological nature of the alteration types was made. The data obtained revealed no lake or age dependency of the observed alterations. Based on the results obtained, we suggest that the presence of endocrine disruptors in the environment or/and genetic factors could be responsible for these kinds of gonad anomalies. However, our results did not allow us to determine the aetiology of the alterations.

Occurrence of Nematodes in the alimentary tract of great cormorants [Phalacrocorax carbo (Linnaeus, 1758)] in colonies located in the upper and lower Vistula River

Abstract The occurrence of nematodes in the alimentary tract of great cormorant Phalacrocorax carbo (L., 1758) nestlings was studied in the Włocławek Reservoir located on the Vistula in central Poland and in adult birds wintering in the south of Poland, with the food base in the upper Vistula. Mixed (max 4 species) nematode infections were found in all birds. Apart from Contracaecum rudolphii Hartwich, 1964 found in all studied birds, the third- and fourth-stage larvae as well as adult individuals of the following species were also present: Eustrongylides excisus Jägerskiöld, 1909, Anisakis simplex (Rudolphi, 1809), Hysterothylacium aduncum (Rudolphi, 1802), Desmidocercella numidica Seurat, 1920, Synquaria squamata (Linstow, 1883), Cosmocephalus obvelatus (Creplin, 1825), Baruscapillaria carbonis (Dubinin et Dubinina, 1940). The overall mean intensity of infection with nematodes was 23.4 ± 11.6 in nestlings and 175.7 ± 110.9 in adult cormorants. The most common species was C. rudolphii with the mean infection intensity of 12.5 ± 5.9 in nestlings and 154.6 ± 111.4 in adults. The second most common species was E. excisus. S. squamata, C. obvelatus and D. numidica were less common in both age groups. A. simplex and H. aduncum were found only in nestlings, while B. carbonis only in adults.

Alizarin mark retention in the otoliths of whitefish (Coregonus lavaretus f. lavaretus L.) from Lake Łebsko, Poland

During the spawning migrations of whitefi sh (Coregonus lavaretus f. lavaretus L.) to Lake Łebsko in Poland during 2009 and 2010, a total of 276 individuals was caught and analysed to determine the retention time of alizarin red S (ARS) marks in their otoliths following marking in 2004 and 2005. ARS marks were visible in the otoliths of 89 specimens, with the oldest fi sh having an age of 5 +. Such mark retention of in excess of 5 years means that bath-marking with ARS is a valuable method for monitoring whitefi sh from Lake Łebsko during a current recovery programme for this endemic population.