Fauna norvegica

A long-term study of the impact of the invasive species Eurasian minnow Phoxinus phoxinus on brown trout Salmo trutta production in a high mountain lake, Southern Norway

2024-03-11T21:23:47+00:00

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 of
the 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.

Brachiopods of the northern North Atlantic and Arctic, with a focus on Norwegian fauna

2023-12-07T07:11:38+00:00

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.

Radiocarbon dating of naturally shed reindeer antlers melted out of retreating and down-wasting ice patches and ice caps in western Norway

2024-05-16T07:40:26+00:00

A rise in summer temperatures, especially since the turn of the 21^st 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.

Diversity of nudibranchs in shallow water habitats in the region of Tromsø, northern Norway

2024-05-08T10:32:51+00:00

Baseline data on the distribution of marine species is crucial to be able to address biogeographical patterns and to monitor changes in species occurrences in marine systems. Nudibranch mollusks have proved to be useful bioindicators for monitoring shifts in distribution and have received much attention by the scientific community in recent years. Being positioned in a zoogeographic transition zone between boreal and Arctic regions, northern Norway is an important area for detecting and tracking early distributional shifts. Despite this, no comprehensive knowledge on current biodiversity and distribution of nudibranchs exists from the region. This work presents, for the first time, an annotated and illustrated inventory of nudibranchs in shallow water habitats of the Tromsø region in northern Norway. In total, 49 different nudibranch species or taxa belonging to 19 different families were recorded during the time period May 2020 – December 2023. Compared to occurrence data from literature records and online data sources, 31 species are here reported from the region for the first time. In addition, northern range extensions are presented for a significant part of the Norwegian nudibranch fauna. By documenting current biodiversity and distribution the present study hopes to serve as a baseline for studies focused on monitoring biodiversity in the Arctic region in the future.

Paralumbricillus gen. nov. and other new marine enchytraeids from the North Atlantic

2024-06-17T18:43:50+00:00

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.