Lumbricillus is one of the largest enchytraeid genera and its species can mainly be found on the coasts of temperate and polar regions around the world. However, the monophyly of the genus has been questioned by recent molecular studies. In this paper we further examine the phylogenetic relationships of Lumbricillus species and their close relatives by estimating a phylogeny of 62 species, many collected along the Norwegian coastline, with seven genetic markers. We confirm Lumbricillus to be non-monophyletic and resolve this issue by establishing the new genus Paralumbricillus, into which ten of the known species are transferred: Paralumbricillus arenarius, Paralumbricillus cervisiae, Paralumbricillus christenseni, Paralumbricillus crymodes, Paralumbricillus dubius, Paralumbricillus eltoni, Paralumbricillus eudioptus, Paralumbricillus muscicolus, Paralumbricillus nielseni, Paralumbricillus westheidei, all comb. nov. In this paper we also describe eight new species: Lumbricillus bibulbus, L. boreas, L. elisae, Paralumbricillus bicornis, P. bilobatus, P. lofotensis, P. sanguineus, and Claparedrilus torquatus.

A rise in summer temperatures, especially since the turn of the 21st century, has caused negative mass balance and marginal retreat of ice caps and ice patches in western Norway. Twentytwo naturally shed reindeer antlers found at retreating and down-melting margins of fourteen retreating ice patches and ice caps on mountain summits in western Norway during the recent decades have been radiocarbon dated. The reindeer antlers show no evidence of being sawed or cut off the skull or any engravings/scrape marks if the antlers had been handled by humans. The oldest reindeer antler in this study dates at 2201-2132 cal. yr BCE. Four dated antlers fall within the age range 2300-2000 cal. yr BCE. Single dates fall within the time ranges 1100 to 1000, 900 to 800, and 500 to 300 cal. yr BCE. Four dated antlers are within the time range 200 BCE to 100 cal. yr CE and two dated antlers fall within the time range 600 to 800 cal. yr CE. Finally, fifteen dates fall within the time range 1300-1900 cal. yr CE, the highest number (n=11) between 1300 and 1600 cal. yr CE. The temperature decline and increased precipitation causing advancing glaciers and ice caps, accompanied by growing ice patches during the Neoglacial period, including the early phase of the Little Ice Age, provided good preservation conditions for the reindeer antlers during the Little Ice Age, with extensive ice and snow cover in the high mountains in western Norway.

Ten species of Brachiopoda have been found living around Norway, including the Arctic Svalbard and Jan Mayen, while 26 are recorded here for the region extending from the Arctic Ocean in the North to the northernmost North Atlantic and Celtic Sea in the South. This paper provides an identification key and short descriptions for all species, including the new species Xenobrochus islandicus n. sp. from southwest of Iceland and the new East Atlantic species Dallina lusitanica n. sp. The distributions of all species have been reviewed and were generally found to follow the oceanic temperature, salinity and depth gradients of the region. Also organic enrichment had some influence on distribution. Some species have shown a possible ongoing northward shift of their biogeographic boundaries over the last two centuries, including the Arctic to subarctic species Hemithiris psittacea.

The shallow Lake Skjerja was originally one of the most outstanding brown trout lakes on the Hardangervidda mountain plateau. During the period 1973–1985, the annual yield was on average 3.35 kg ha-1. In the mid-1980s, Eurasian minnow established a dense population in the lake. Since 1994, 5304 kg of Eurasian minnow have been removed with baited traps, which correspond to an annual mean catch of 177 kg year-1 or 1.12 kg ha-1. The competition for food, in addition to longer food chains, has had a strong negative impact on the brown trout production, with an annual yield reduced to 1.07 kg ha-1, or 32% of the historical catches (1973-1985). The total removed biomass of the two fish species correspond to 65% of the brown trout yield before the invasion of the Eurasian minnow. In Lake Skjerja, the two crustacean species Gammarus lacustris and Lepidurus arcticus, have historically been staple food items for brown trout. Fishing with baited traps on the minnows, and the presence of a large fraction of predatory brown trout, may have reduced the predation pressure on the two crustacean species, and they are still a part ofthe brown trout diet. The availability of fish as food has resulted in a significant increase in the presence of large individuals of brown trout with maximum weights above four kg. Despite reduced annual yield of brown trout, Lake Skjerja is still a popular fish destination with nearly 200 big-sized brown trout (mean annual weight 1065 grams) landed annually. On Hardangervidda, an increase in air temperature has been observed since the 1980s, with a corresponding change in water temperature which may benefit Eurasian minnow. In warm summers, water temperature approaches 14°C which has proved to be near to the upper thermal threshold for Lepidurus arcticus.

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.

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.

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.

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.

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 Arctic tadpole shrimp Lepidurus arcticus has a circumpolar distribution and the Scandes (Fennoscandian Mountains) marks its southernmost limit in Europe. Within this area, 391 natural and 88 regulated lakes with L. arcticus have been identified, of which 87% are above the treeline. The lakes hosting L. arcticus decrease in altitude from south to north, which results from its temperature preferences. The majority of the locations are at a lower lake air temperature than 11°C which is equivalent to a water temperature near 14°C. This is assumed to be near the upper thermal threshold for L. arcticus. In lakes that exceed this average summer water temperature (1 July – 15 September), sustainable populations seem to be rare. In warmer lakes, life cycle mismatches are assumed to explain the absence of L. arcticus, most likely by affecting the embryo and juvenile stages. The distribution appears to be dichotomous, with one large northern area north of 65°N and one separated southern “island”. Only two locations of L. arcticus are known for the area between latitudes 62.88 and 64.39°N. In this part of the Scandes, the lakes are likely too warm to host L. arcticus as most of them are situated below 700 m a.s.l. This may also be the case in the northernmost region, north of 70°N, where only 11 populations are recorded. Most of the lakes in this area typically occurs below 400 m a.s.l. L. arcticus populations are sensitive to fish predation, and dense fish populations may be another stressor limiting its distribution. In contrast to water bodies in the High Arctic where L. arcticus only exists in shallow, fishless ponds, in the Scandes they co-exist with fish in 97% of the findings. Global warming has already modified the environment of the Scandes, and populations of L. arcticus are at threat in many of the small and shallow water bodies at low altitudes.