Diet composition and seasonal feeding patterns of a freshwater ringed seal (Pusa hispida saimensis)

The Saimaa ringed seal (Pusa hispida saimensis) is one of the few freshwater seal populations worldwide. The major conservation issue of this critically endangered population is bycatch mortality. We used digestive tract content and stable isotopes (d13C and d15N) to estimate the diet and seasonal feeding patterns for gaining better understanding of the seals feeding habits and potential conservation implications. The diet was similar across age groups. Altogether 15 fish species were identified and the most important were smelt (Osmerus eperlanus), ruff (Gymnocephalus cernuus), perch (Perca fluviatilis), vendace (Coregonus albula) and cyprinids. The high d15N values suggested that the seal…

Diet composition and seasonal feeding patterns of a freshwater ringed seal (Pusa hispida saimensis)

The Saimaa ringed seal (Pusa hispida saimensis) is one of the few freshwater seal populations worldwide. The major conservation issue of this critically endangered population is bycatch mortality. We used digestive tract content and stable isotopes (d 13 Ca ndd 15 N) to estimate the diet and seasonal feeding patterns for gaining better understanding of the seals feeding habits and potential conservation implications. The diet was similar across age groups. Altogether 15 fish species were identified and the most important were smelt (Osmerus eperlanus), ruff (Gymnocephalus cernuus), perch (Perca fluviatilis), vendace (Coregonus albula )a nd cyprinids. The high d 15 N values suggested that th…

Benthic‐pelagic coupling and trophic relationships in northern Baltic Sea food webs

Understanding marine ecosystem structure and functioning is crucial in supporting sustainable management of natural resources and monitoring the health of marine ecosystems. The current study utilized stable isotope (SI) mixing models and trophic position models to examine energy flow, trophic relationships, and benthic‐pelagic coupling between food web components. Roughly 1900 samples from different trophic levels in the food web, collected during 2001–2010 from four northern and central sub‐basins of the Baltic Sea, were analyzed for SI ratios of carbon and nitrogen. Trophic structure of the food webs among the sub‐basins was consistent, but there were differences between the proportions …

DNA barcoding reveals different cestode helminth species in northern European marine and freshwater ringed seals

Three subspecies of the ringed seal (Pusa hispida) are found in northeastern Europe: P. h. botnica in the Baltic Sea, P. h saimensis in Lake Saimaa in Finland, and P. h. ladogensis in Lake Ladoga in Russia. We investigated the poorly-known cestode helminth communities of these closely related but ecologically divergent subspecies using COI barcode data. Our results show that, while cestodes from the Baltic Sea represent Schistocephalus solidus, all worms from the two lakes are identified as Ligula intestinalis, a species that has previously not been reported from seals. The observed shift in cestode communities appears to be driven by differential availability of intermediate fish host spec…

Comparison of muscle and hair stable isotope ratios in three phocid seals

Intestinal helminths of a landlocked ringed seal (Phoca hispida saimensis) population in eastern Finland.

A small, landlocked, endangered ringed seal (Phoca hispida saimensis) population lives as a postglacial relict in Lake Saimaa in eastern Finland. In this study, the intestinal metazoans were examined from a total of 61 Saimaa seals found dead from 1981 to 2001. The helminth fauna was very depauperate. Only one acanthocephalan species, Corynosoma magdaleni, has been able to survive during isolation in the freshwater environment. In addition, only two cestode species were found: Diphyllobothrium ditretum and Schistocephalus sp. However, neither of these larvae developed in the ringed seals. As the newborn pups of Saimaa seals are nursed for about 2 months only one of them was infected by C. m…

Accurate spatial ecology of endangered Saimaa ringed seals as a base for fishing closure determination

Saimaa ringed seal (Phoca hispida saimensis) is an endangered subspecies living landlocked in Lake Saimaa, southeastern Finland. One of the major threats of this small population (ca 370 seals) is by-catch due to mainly recreational gill net fishing. For mitigating by-catch mortality varied fishing closures and restrictions have been established in the lake over time. The fishing restrictions cover year round ban of the most dangerous fishing methods and springtime (15.4.-30.6.) gill net ban to protect especially the pups. In this study, we describe the usage of accurate spatial ecology data of the Saimaa ringed seals as a base for conservation measures. Telemetry tracking data of both; juv…