Fauna norvegica

Considerations needed for analysing data from the Swedish Electrofishing RegiSter (SERS), with special reference to the RivFishTIME database of long-term riverine fish surveys

Wed, 20 Dec 2023 00:00:00 +0000

The published database RivFishTIME (Comte et al. 2021, Global Ecology and Biogeography, doi: 10.1111/geb.13210) includes a large section of time-series data on fish abundance in Swedish rivers from the Swedish Electrofishing RegiSter, SERS. Knowledge about the limitations of the source data are important when extracting and analyzing data and with this brief note we provide some details that may be helpful for interpreting the Swedish time-series. The note highlights the importance of linking vital metadata to extracted focal data when constructing new databases, especially concerning time series data from monitoring programs conducted in non-randomly selected sites with human environmental impacts. Many of the SERS data come from rivers that have been affected by human impact, e.g. liming to mitigate environmental acidification and hydropower dams, since before monitoring was initiated. Data in SERS are also biased towards shallow salmonid habitats, due to the configuration of Swedish monitoring programs. Hence, data from many rivers are not representative of their fish biodiversity in general. This information is vital for appropriate interpretation of fish biodiversity trends. For RivFishTIME analyses considerations are important since Swedish data constitutes a large proportion of the database. We also provide background information about SERS and references to other Swedish databases containing complementary information. Finally, we provide contact information of the SERS database curators, who can assist prospective analysts with data extraction from SERS.

Annual growth of brown trout in alpine lakes is highly influenced by spring snow depth and ice-out day

Reidar Borgstrøm — Tue, 24 Oct 2023 00:00:00 +0000

Growth of annular zones in otoliths of brown trout from the alpine lakes Litlosvatn and Kollsvatn on western part of the Hardangervidda mountain plateau have been studied during the period 2004–2021, concurrent with recordings of accumulated snow in spring and dates of ice-out. Unlike the conditions in lowland areas, years with much accumulated snow have not decreased during the last decades, and years with delayed ice break-up are still frequent, opposite the trend observed elsewhere in Europe and in North America. The annual growth of the brown trout otoliths is significantly reduced in years with much snow in April and late ice-out dates, irrespective of age of the fish, indicating that somatic growth of brown trout is considerably reduced in such years. Accumulated snow in spring and ice-out day may thus be useful parameters in predictions of fish production and potential yield in such alpine lakes.

Distribution of the gill parasite Discocotyle sagittata (Monogenea: Polyopisthocotylea) in parr of Atlantic salmon Salmo salar and sea trout S. trutta in Norwegian rivers

Tor Atle Mo — Tue, 24 Oct 2023 00:00:00 +0000

The monogenean gill parasite Discocotyle sagittata is reported from parr of Atlantic salmon Salmo salar and sea trout S. trutta in the anadromous part of 86 out of 223 Norwegian rivers. The prevalence in each river varied from 1.5% to 88.9%. This study has significantly increased our knowledge about the occurrence of this salmonid parasite in Norway. Most likely, D. sagittata has a much wider distribution all over the country and probably also occur in numerous inland lakes, rivers and streams.

A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980-2020

Leif Asbjørn Vøllestad — Tue, 28 Feb 2023 00:00:00 +0000

Norwegian freshwater systems are in general species poor. That is particularly the case for the freshwater fishes. Only 32 species are considered native, whereas an additional 12 species are non-native. Some of the non-native species are also considered to be invasive and have negative ecosystem effects. Freshwater fishes are exposed to numerous stressors through their life cycle, many of which are of anthropogenic origin. In order to manage and conserve the diversity of fish there is a need for basic knowledge and understanding. Here I make an effort to review the published research on all Norwegian freshwater fish species during the 1980-2020 period, based on a standardized search on the Web of Science. Over 2000 relevant articles were retrieved and evaluated following the search. The research activity has been highly biased, with most research activity directed at a few species of high economic and societal value. Most work was directed at Atlantic salmon Salmo salar and brown trout S. trutta, and in general towards species within the salmonid family. Extremely little attention was directed at species such as the lampreys (four species) and sculpins (three species). Also, many species that has been listed on the Norwegian Red List during various time periods has not been given any particular attention. This lack of attention was also evident for most of the non-native species. The strong bias in research activity and lack of attention given to many species will clearly lead to difficulties in making appropriate management decisions. This is unfortunate, in particular in a time when climate change may lead to numerous ecosystem level changes.

The first record of Gyraulus cf. acronicus (Gastropoda, Heterobranchia, Planorbidae) in waterbodies of the Novaya Zemlya Archipelago

Nadezda B. Ovchankova, Andrey B. Krasheninnikov — Tue, 28 Feb 2023 00:00:00 +0000

The knowledge on diversity of freshwater molluscs in the Arctic islands of the Russian Federation remains incomplete. The present study provides the first record of the North Palaearctic species Gyraulus cf. acronicus (Férussac, 1807) on the Novaya Zemlya Archipelago. It is also the first finding of freshwater gastropods on the archipelago and the northernmost record for Gyraulus in the Palaearctic Region. The questions still remain: whether our finding belongs to a recent or a subfossil or fossil population, and how gastropods could colonize the Arctic islands. Several possibilities of dispersal are discussed: the former land-bridge once connecting the archipelago islands to the mainland, and the dispersal of snails with other animals after the Ice Sheet retreat.