identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
371087DDA25AFFE7FF213F2AFE95FAFB.text	371087DDA25AFFE7FF213F2AFE95FAFB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Petromyzontidae Bonaparte 1831	<div><p>Petromyzontidae</p><p>A total of four lamprey species has been registered in Norwegian freshwaters. Two of these species (sea lamprey, arctic lamprey) have regularly been listed on the Norwegian Red List for Species (see Table 1). Both are still listed in 2021, with the sea lamprey listed as near threatened (NT) and the arctic lamprey as vulnerable (VU). However, only one article has been registered in the Web of Science during the 1980-2020 time period. This paper reports on lamprey as food for pike Esox Lucius Linnaeus, 1758, and it is unclear if it relates to brook lamprey Lampetra planeri (Bloch, 1784) or river lamprey L. fluviatilis (Linnaeus, 1758) (Sandlund et al. 2016b) . What else is known about these species is usually published in Norwegian-language technical reports. Information on the distribution of two of the species (sea lamprey and brook lamprey) have recently been summarized in a Norwegian popular science journal (Hesthagen et al. 2020, Hesthagen et al. 2021a). In total, however, there is a complete lack of basic biological knowledge about these four species in Norwegian lakes, rivers and streams.</p></div>	https://treatment.plazi.org/id/371087DDA25AFFE7FF213F2AFE95FAFB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA25AFFE4FF203949FDD9FCFB.text	371087DDA25AFFE4FF203949FDD9FCFB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Cyprinidae A. d'Orbigny 1844	<div><p>Cyprinidae, Leuciscidae, Gobionidae and Tincidae</p><p>These four families were earlier considered to belong to one single family – Cyprinidae . I therefore, for simplicity, treat them together here. A total of 16 species belong to these families, whereof five species are introduced and non-native (Table 1). On average only three papers were published for each of the non-native species, compared with on average 11 articles for the native species. However, the number of articles published for the native species was very biased, with most articles being published for only four species (roach Rutilus rutilus (Linnaeus, 1758), Eurasian minnow Phoxinus phoxinus (Linnaeus, 1758), bream Abramis brama (Linnaeus, 1758), crucian carp Carassius Carassius (Linnaeus, 1758)) .</p><p>Both the roach and the minnow are classified as regionally non-native species and suggested to have a high to very high ecological risk to the local ecosystem. However, few of the articles on the roach were relevant in order to evaluate the effect of translocations, but were rather classical ecological studies (L’Abée-Lund and Vøllestad 1985, Vøllestad and L’Abée-Lund 1987, L’Abee-Lund and Vøllestad 1989). Further, most of these studies was published during the period 1980- 1995. This was a time when biomanipulation of freshwater ecosystems in order to increase water quality was popular (Carpenter and Kitchell 1992, DeMelo et al. 1992); this was evidently the focus for some of the studies (Brabrand et al. 1990, Faafeng et al. 1990, Brabrand and Faafeng 1993). During recent years, most of the retrieved studies actually did not focus on the roach, but information on the roach was rather a by-product of the main topic of the study. The listing of roach as a species with potentially high ecological impact when translocated to new locations has seemingly not led to more studies. However, in 2021 a new study trying to forecast the distribution of roach was published (Perrin et al. 2021). This study also discussed several other species that are considered as regionally invasive.</p><p>The Eurasian minnow has been studied in different contexts. Most studies are set in an ecosystem context, with focus on predator-prey relationships (Borgstrøm et al. 1985, L’Abée-Lund et al. 1996) and parasite-host dynamic (Museth 2001, Pettersen et al. 2016, Borgstrøm et al. 2017). It has been a clear focus on the interaction between the minnow and the native fish fauna, in particular interactions with the brown trout (Lien 1981, Museth et al. 2007). During recent years there has been an intensive action by various management authorities to reduce the spread of the minnow to new locations (Museth et al. 2007), but it has only to limited degree led to increased and relevant research activity on the species.</p><p>The crucian carp is also classified as regionally non-native, but it is assumed to have only low ecological effects in the new environment. Most of the reported studies are focused on the particular physiology of the crucian carp (Sollid et al. 2005), in particular its ability to survive long periods without oxygen (Poléo 1993). This ability also makes the species very tolerant to high concentrations of labile aluminium at low pH (Poléo et al. 2017). Also, the fact that the crucian carp develop different body shapes in the presence or absence of gape-limited predators has attracted some attention (Poléo et al. 1995). However, no studies up to 2020 focused on the crucian carp as a regionally invasive species with potential negative effects. Such studies seem to appear more recently (de Meo et al. 2022).</p><p>A total of 11 articles were found to report data on the bream – indicating at least some interest in this species. Almost 50% of these articles are from the National History Museum at the University of Oslo, and focus on distribution, feeding and parasites (Brabrand 1984, Brabrand et al. 1994, Sterud and Appleby 1996). The bream is an important component of many large lakes in the south-east part of Norway. It is therefore strange that so little attention has been diverted to learn more about its ecology, and potential interactions with other species.</p><p>The rudd Scardinius erythrophthalmus (Linnaeus, 1758) is classified as a regionally non-native species with a potential for very high ecological effects. However, in total only four articles have been published on this species. None of these studies focused on ecosystem effects or on potential interactions with native species. However, the potential future establishment of this species was evaluated in a 2021 study (Perrin et al. 2021).</p><p>The five non-native species in these families are classified as having variable ecological risks (Table 1). Three species were classified as having high ecological risk following translocation, and the other two were assumed to have limited ecological risk. However, only a very limited number of papers (varying from 2-7) was published for each of the species. For the carp Cyprinus carpio Linnaeus, 1758 a total of seven papers were registered. Most of these papers were notes of the present and historical distribution of carp (Kålås and Johansen 1995, Kleiven 2013), but there was no paper on its ecology and interaction with other species. For the tench Tinca tinca (Linnaeus, 1758), one paper on age and growth was found (L’Abée-Lund 1985). For the three other species (sunbleak Leucaspius delineates (Heckel, 1843), gudgeon Gobio gobio (Linnaeus, 1758), goldfish Carassius auratus (Linnaeus, 1758)), no study on ecology was found. In total, for most of the species that was classified as either non-native and invasive at the national scale or at the regional scale very limited ecological information has been gathered during the period 1980-2020.</p><p>Two species were classified on the Norwegian Red List during 2006 (Table 1), but not on the later iterations of the list. Thus, I would assume that some ecological information had been gathered to facilitate this new evaluation. The silver bream Blicca bjoerkna (Linnaeus, 1758) was classified as NT in 2006. However, only four papers focusing on this species were found – the newest from 1996. This paper was on parasites (Appleby and Sterud 1996). The asp Aspius aspius (Linnaeus, 1758) was classified as VU in 2006. Only two papers were found for this species, one on a potential observation in a new location (Spikkeland and Basnes 2009), and one on parasites (Sterud and Appleby 1996). Thus, basically no relevant information has been published formally either before or after the Red list listing.</p><p>For the remaining species in these four families very little published information could be found. In total, the information available is very biased towards a few species. Even the non-native species with suggested high ecological risks (impacts) have not been studied to any extent. This is, of course, unfortunate.</p></div>	https://treatment.plazi.org/id/371087DDA25AFFE4FF203949FDD9FCFB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA259FFE4FF203969FA92FE3B.text	371087DDA259FFE4FF203969FA92FE3B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Esocidae Rafinesque 1815	<div><p>Esocidae</p><p>The pike is a common species both in south-eastern and northern Norway. As a top predator it usually attracts attention, but still only 30 articles were found based on the standard search. If I included articles by Norwegian researchers working on pike in other countries the numbers would have been much higher (for example see Haugen et al. 2006, Carlson et al. 2007, Edeline et al. 2007, Haugen et al. 2007).</p><p>The ecology of the pike is well known (Skov and Nilsson 2018). In Norway, studies have to some degree focused on pike diet and thus its ecosystem effect as an apex predator (Vøllestad et al. 1986, Sandlund et al. 2016b). Some papers also investigate the ecological effects of various management actions, such as the effect of size-selective harvesting (Sharma and Borgstrøm 2008a). Such selective harvesting may also have unexpected effects on the accumulation of pollutants such as methyl-mercury (Sharma et al. 2008). As a top predator such pollutants may be up-concentrated in large and old individuals (Frøslie et al. 1985, Sharma et al. 2009, Olk et al. 2016), potentially posing a risk to human health. In total, even if the number of published papers is relatively small, the level of ecological knowledge on the pike is in general good.</p><p>The pike has repeatedly been translocated outside of its native area, and is classified as a regionally non-native species with a potentially very strong ecological effect (Table 1) (Byström et al. 2007, Hesthagen et al. 2015, Dunker et al. 2018, Jalbert et al. 2021, Perrin et al. 2021). Our knowledge about the ecological effects of new introductions seems adequate, but still some main understanding of their population dynamics is missing for Norwegian conditions. In particular, more knowledge about the effects of pike introduction into species poor and cold environments is needed. Clearly, also a better understanding of the invasion dynamics, such as dispersal dynamics and the drivers on long-distance translocations is needed.</p></div>	https://treatment.plazi.org/id/371087DDA259FFE4FF203969FA92FE3B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA259FFE4FF203F49FE28FA9B.text	371087DDA259FFE4FF203F49FE28FA9B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Ictaluridae Gill 1861	<div><p>Ictaluridae</p><p>The brown bullhead Ameiurus nebulosus (Le Sueur, 1819) is a non-native species with a limited distribution in Norway. The only published information is actually on its national distribution (Hesthagen and Sandlund 2007, Hesthagen and Brabrand 2018). The brown bullhead has a very constricted distribution, and it does not seem to have expanded much since the early 1900s (Huitfeldt-Kaas 1918). However, some expansion has happened – mainly locally. The brown bullhead has been categorized as an non-native species with a limited potential for negative ecological effects (Forsgren et al. 2018). In spite of it being a non-native species in Norway there is no information on its ecology in Norwegian lakes and thus also no studies that can document how and to what degree it influences other fish species or other organisms.</p></div>	https://treatment.plazi.org/id/371087DDA259FFE4FF203F49FE28FA9B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA259FFE4FC823D89FBF8FABB.text	371087DDA259FFE4FC823D89FBF8FABB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Osmeridae Regan 1913	<div><p>Osmeridae</p><p>The smelt Osmerus eperlanus (Linnaeus, 1758) is an important component of the food web in many lakes in south-east Norway. Several of the 22 studies that was retrieved by the search in some way evaluated the smelt in an ecosystem context, either as food for other fish (Garnås 1983, Sandlund et al. 2005, Eloranta et al. 2019) or as a predator on zooplankton (Sandlund et al. 1987, Hessen et al. 1988). As it is prey for economically important species such as brown trout there has also been some interest in how smelt accumulate pollutants (Frøslie et al. 1985, Skurdal et al. 1985).</p><p>There are also some studies on the present-day distribution of smelt, discussing either the presence of new locations following translocations (Hagenlund et al. 2015) or the potential rediscovery of populations in locations where it was considered extinct (Kleiven 2000). This small-sized species is usually easy to see during the spawning season, or as food items in the stomach of predatory fish. However, as the species is small-sized, it can be overlooked when density is low or if fishing effort is limited.</p><p>The smelt is a very important player in the local food web, both as food for various predatory fishes and as an efficient zooplankton feeder. Thus, the smelt can be called a keystone species (Lammens et al. 1990, Sandlund et al. 2005), in the same way as the close relative the capelin Mallotus villosus (Müller, 1776) is a keystone species in the arctic marine environment (Hjermann et al. 2010). Given this, it should be important to know the dynamics of the smelt populations to better predict transfer of energy through the lake food web. However, such studies could not be found.</p></div>	https://treatment.plazi.org/id/371087DDA259FFE4FC823D89FBF8FABB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA259FFE5FC823909FDD2FA9B.text	371087DDA259FFE5FC823909FDD2FA9B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Salmonidae Jarocki or Schinz 1822	<div><p>Salmonidae</p><p>A total of 11 species belonging to the Salmonidae family are registered in Norway. Of these, five species are non-native. As shown in Figure 3 this family in strongly over-represented when it comes to research effort as determined by number of publications. For most of the native species, I found a relatively high number of publications with Atlantic salmon on top, followed by the brown trout and the Arctic char (Figure 5).</p><p>The non-native species are on average little studied, listing between one and 15 publications per species during the whole period (Figure 5) The chum salmon is probably not established with reproducing populations in Norway, whereas the pink salmon Oncorhynchus gorbuscha (Walbaum, 1792) has appeared in large numbers during even years lately (Mo et al. 2018, Sandlund et al. 2019). Management authorities has initiated large efforts to keep the pink salmon invasion at bay, and this might lead to more publications on this species in the years to come. For example, interesting questions arise on how energy in transferred from the marine environment to the freshwater and terrestrial environments as large numbers of carcasses of pink salmon decomposes (pink salmon are semelparous) (Dunlop et al. 2021a, Dunlop et al. 2021b). Studies in order to understand the population dynamics of this species is underway (Paulsen et al. 2022). It is more worrying that there is so little information on species such as the rainbow trout O. mykiss (Walbaum, 1792), lake trout Salvelinus namaycush (Walbaum, 1792) and brook char S. fontinalis (Mitchell, 1815) (but see Hesthagen et al. 2018). These species have been present in Norwegian freshwaters for decades, but still very little is published on their biology and potential interaction with other species. The rainbow trout is classified as having a high ecological risk, whereas both the lake trout and the brook char has low risk. In total, it is worrying that the ecology of these three species basically in unknown in Norwegian freshwater systems.</p><p>Six salmonid species are categorized as native to Norway. The two species belonging to the Salmo genus, Atlantic salmon and brown trout, are extensively studied both in Norway and globally (Table 1). For both species I retrieved more the 500 publications for the 1980-2020 time period. Further, the Arctic char was treated in 320 publications, whitefish Coregonus lavaretus (Linnaeus, 1758) in 98 publications and the vendace C. albula (Linnaeus, 1758) in 50 publications. The grayling Thymallus thymallus (Linnaeus, 1758) is the least studied of these species, with only 37 publications listed. These six species, however, deserve separate chapters.</p></div>	https://treatment.plazi.org/id/371087DDA259FFE5FC823909FDD2FA9B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA258FFEAFF213969FB8FFE5B.text	371087DDA258FFEAFF213969FB8FFE5B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Salmo salar Linnaeus 1758	<div><p>Atlantic salmon Salmo salar Linnaeus, 1758 .</p><p>The Atlantic salmon is the species which has received by far the most attention by fish biologist in Norway. Also, the publication rate (number of published articles per year) has increased significantly (number or articles per year; linear regression, R 2 = 0.396, slope = 0.37 ± 0.07, P &lt;0.001). This interest has also manifested itself globally by the publication of several books (Aas et al. 2011, Jonsson and Jonsson 2011). The large interest in Atlantic salmon is due to many factors, both economic, societal and political. Without going into detail here, there are large conflicts about how to manage and conserve the wild populations in the face of numerous challenges (Forseth et al. 2017). A major factor leading to conflicts is the interaction between the Atlantic salmon farming industry and the local wild populations (Liu et al. 2011). This has led to the build-up of large conservation plans with associated programs for collecting relevant data. Further, specific fjords and rivers are set aside where fish farming and other encroachments should not be allowed (Vøllestad et al. 2014, Vøllestad et al. 2018). All in all, this long-term interest and level of conflict has led to the production of a large number of articles on the Atlantic salmon – and as shown earlier, the numbers are increasing.</p><p>I tried to classify the articles into different topics – ending with classifying them as either mainly focussing on behaviour, ecology, evolution including genetics, management, or on the effect of pollution (Figure 6). It was not easy to do this classification, as many publications are at the interface between topics. However, the exercise probably gives an indication of temporal changes in scientific focus.</p><p>Throughout the 40 years covered by this summary a large proportion of the published papers could be classified as mainly ecological. Without going into details, it was clear that early in the period focus was on the freshwater part of the life cycle – studying topics such as growth, survival and habitat use of juveniles (Jensen and Johnsen 1985, Berg and Gausen 1988, Heggberget 1988, Heggenes et al. 1991). More recently there has been more focus on the marine phase – mainly by the inclusion of modern methods like telemetry (Haraldstad et al. 2017, Halttunen et al. 2018), electronic tags of different kinds (Hedger et al. 2017, Strøm et al. 2017, Strøm et al. 2020), and different types of state-of-the-art modelling (Vøllestad et al. 2009, Otero et al. 2011, Castellani et al. 2018). It is also evident that focus has changed from local-scale studies in individual rivers to more regional and global scales. Local scale studies also tend to become more long-term and focussing on mechanisms. These changes in publication pattern to a large degree follow general trends in many ecological fields, where focus has changed from descriptive small-scale studies to studies focussing on hypothesis testing and synthesizing data over larger temporal and spatial scales.</p><p>Behaviour was a topic of interest in particular in the 1980-2000 time period. These studies were focussed on two particular types of behaviours: migration mainly in freshwater (rivers and lakes), and spawning behaviour. The study of downstream migration of smolt has always been interesting, often set in a phenological context (Hansen et al. 1984, Jonsson and Ruud-Hansen 1985, Hvidsten et al. 1995). Also the upstream migratory behaviour of adult fish have been studied (Heggberget et al. 1993, Lennox et al. 2018). More recently, studies on the swimming behaviour of post-smolts through fjords and older salmon at sea also have been published (Økland et al. 2006, Manel-La et al. 2009). These studies have been facilitated by the development and use of acoustic telemetry, pop-up satellite tags and data storage tags. Several such studies have appeared recently (Strøm et al. 2020, Rikardsen et al. 2021), and more is expected following larger research programs that have been initiated. More classical behavioural studies were uncommon.</p><p>Evolutionary questions have been studied throughout the period, but in particular during later years. In this context I include studies on population genetics. During the early period some studies focusing on genetic structure (Vuorinen and Berg 1989, Skaala et al. 1998) and its relation to aquaculture (Hindar and Balstad 1994, Garant et al. 2003) was published, however usually with limited scopes and limited sets of genetic markers. This was probably due to lack of proper and economically available methods. Recent developments in methods and collaborations have led to many studies on both the general genetic structure of the Atlantic salmon (Vähä et al. 2017, Wennevik et al. 2019), and the level of interaction with aquaculture (Glover et al. 2013, Zhang et al. 2013, Glover et al. 2018). Many studies in the last category are here classified as focused on management (see below). Numerous studies from the river Tana (Teno) were not retrieved in the search because it did not fit the search criteria, or because they were published after 2020. Also, the publication of the annotated full genome of the Atlantic salmon was not picked up by the search (Lien et al. 2016). However, these publications are important in an international context, as they either produce high-quality results or may help develop major tools for a diverse set of later studies (Ayllon et al. 2015, Barson et al. 2015, Czorlich et al. 2018). These last studies are trying to understand major evolutionary questions, rather than more local scale questions of applied importance. Overall, also in the published studies that were retrieved by the search such a change from local to global scale questions is evident. Also, studies of more functional character have appeared, such as on the genetic resistance to sea lice (often called salmon lice) Lepeophtheirus salmonis (Krøyer, 1837) infections (Kolstad et al. 2005), the genetic consequences of inbreeding (Roberge et al. 2008), and regulation of growth (Besnier et al. 2020).</p><p>Research focusing on issues related to management has increased in number with time – this is to a large degree related to the increased conflict between wild salmon interests (conservation and recreational fisheries) and the Atlantic salmon farming industry (Forseth et al. 2013, Forseth et al. 2017). In the earlier part of the time period, management-related research was usually on the effect of hydropower development (Brooks et al. 1989, Raddum and Fjellheim 1995, Saltveit et al. 2001), managing of the commercial and recreational fishery (Jensen et al. 1999, L’Abée-Lund and Aspås 1999, Thorstad et al. 2007), or the handling of local and regional infestations of the ectoparasite Gyrodactylus salaris Malmberg, 1957 (Johnsen and Jensen 1991, Pettersen et al. 2013, Sandodden et al. 2018). These types of studies have continued to be important throughout the period investigated. However, in the recent decades focus has also been centred on the interaction between wild populations and the salmon farming industry. The two main topics are the effect of escapement of farmed fish into rivers (Skilbrei et al. 2015, Diserud et al. 2019), and the effect of sea lice on wild fish (Torrissen et al. 2013, Kristoffersen et al. 2018). Even if management-oriented studies are published at a reasonably high pace, most of the ongoing research is still published in the grey literature and not picked up in my search.</p><p>The final topic that I grouped the papers into was pollution – or rather the effect of pollution. The popularity of such studies seems to have decreased with time, or the pollution problems are becoming less important. In the 1980s acidification was a problem in freshwaters, also in Atlantic salmon rivers (Skogheim et al. 1984, Rosseland et al. 2001, Hesthagen and Larsen 2003, Hesthagen et al. 2011b). The problem has to a large degree been mitigated, either due to reduction in emissions of acidifying compounds or due to local mitigating actions (liming) (Sandøy and Langåker 2001). There was also a small burst in publications on the distribution and effect of radiocaesium following the Chernobyl accident (Forseth et al. 1998), but the focus was rarely on Atlantic salmon.</p><p>Overall, the publication rate on the Atlantic salmon has been high and is still increasing. Still, the wild populations overall are not doing well. This led to listing of the Atlantic salmon as being near threatened (NT) on the 2021-version of the Norwegian red list (Hesthagen et al. 2021d). On previous versions of the red list the Atlantic salmon was not listed. So, despite extensive efforts by numerous management authorities and organizations, and extensive research activity, the situation is not becoming better. And this is the situation for the species where most basic ecological information is available for any Norwegian freshwater fish, and where most research activity and funding has been directed.</p></div>	https://treatment.plazi.org/id/371087DDA258FFEAFF213969FB8FFE5B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA257FFEBFC823E29FA80FBB8.text	371087DDA257FFEBFC823E29FA80FBB8.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Salmo trutta Linnaeus 1758	<div><p>Brown trout Salmo trutta Linnaeus, 1758</p><p>The brown trout (hereafter trout) is the most widely distributed freshwater fish in Norway (Huitfeldt-Kaas 1918). It is very popular for sports fishing, and was historically extensively used for household fishing. Numerous books have been written about it, both nationally (Qvenild 1994, Nilssen 2017) and internationally (Elliott 1994, Jonsson and Jonsson 2011, Lobón-Cerviá and Sanz 2018). This large interest has also led to extensive research efforts in Norway during the 40-year time period checked here (Table 1).</p><p>A total of 528 publications was retrieved by the search, leading to more than 12 publications per year during the 40-year period. There was a weak increase in the number of publications per year during the period (linear regression, R 2 = 0.152; slope 0.16 ± 0.06, P = 0.012). Over 50% of the retrieved publications could be classified as focusing on ecology, and ecological studies have been published with more or less the same frequency throughout the time period (Figure 7). Studies on behaviour have, on the other hand, been relatively few, and most of these studies were on migration and movement.</p><p>Evolutionary studies were rare in comparison to the ecologically focused studies. Almost all of the studies that could be classified as evolutionary were focused on population genetics of some kind. Over time these studies use different methods, most were analysing variation in allozymes and microsatellites (Skaala and Jørstad 1987, Skaala and Solberg 1997, Sønstebø et al. 2007, Serbezov et al. 2012b, Vøllestad et al. 2012). Most studies were at relatively small geographic scales (within river systems) and focus on classical fixation index estimations (FST), and thus gene flow and level of differentiation on putatively neutral makers. These studies can to some degree be put into a conservation genetics context. Some studies also estimated directly relevant parameters such as the effective population size (Serbezov et al. 2012a, b) or more directly assess the effects of for example habitat fragmentation (Junge et al. 2014) or introgression from stocked fish (Sønstebø et al. 2008). The limited scale of many of these studies, as also was common in northern Europe in general (Vøllestad 2018), contrasts the current trend for the study of Atlantic salmon, and limits the understanding of the genetic structure of the trout at the national scale. This is unfortunate, as it makes it difficult to take part in the ongoing and heated discussion on the phylogenetics of the trout (Bernatchez 2001, Kottelat and Freyhof 2007, Sanz 2018, Guinand et al. 2021). It is also unfortunate that more modern genetic methods have not been used to any degree.</p><p>A limited number of studies have also taken a more quantitative or life history approach. Such studies are clearly useful for understanding how trout may respond to various selective forces (Haugen et al. 2008, Robertsen et al. 2011). It may also help in understanding to what degree genetic architecture and phenotypic plasticity determine life history decisions (resident vs migratory) (Jonsson 1982, Jonsson et al. 1994). The trout is often highly migratory, and it is important as an anadromous species along the coast. However, very few studies address questions related to variation in level of anadromy. Even the few studies that were classified as behavioural did rarely include the marine phase of life (but see later in relation to management).</p><p>Trout are found in all kinds of freshwaters throughout Norway. And over time it has been exposed to numerous pollutants, with variable effects on individuals and populations. In the early part of the investigated period the effect of acid rain and subsequent acidification of surface waters were studies by many. The studies focused on individual level effects (Rosseland and Skogheim 1984, Rosseland et al. 1986, Muniz et al. 1987), population level effects (Hesthagen 1986, Muniz 1991, Bulger et al. 1993, Barlaup and Åtland 1996), and mitigation measures (Rosseland and Hindar 1988, Traaen et al. 1997, Hindar and Wright 2005). Studies of acidification has become rare during the last years. There are two additional topic that have been investigated by Norwegian researchers – the effect of the Chernobyl accident, and heavy metal pollution. The trout is the freshwater fish that was most studied in order to understand the dynamics of radioactive caesium in the environment (Ugedal et al. 1997, Forseth et al. 1998, Jonsson et al. 1999, Braaten et al. 2019). Such studies were limited in time. However, studies on the importance of mercury in fish and in the environment as such is still ongoing (Skurdal et al. 1985, Amundsen et al. 1997, Olsvik et al. 2001, Thomas et al. 2016). In total 75 of the articles that were retrieved from the search could be classified as focusing on pollution issues.</p><p>As a widely distributed and sought-after species, there was a large number of studies with a management perspective. More than 110 such studies were retrieved by the query. In particular, numerous studies have investigated the various effects of hydropower development. Such development, with the building of dams and changing of water flow will impact on connectivity, habitat quality and habitat availability. This is an ongoing issue for study, and will probably be so given the recent incentives to develop more so-called green energy (Aass et al. 1989, Heggenes and Saltveit 1996, Halleraker et al. 2003, van Leeuwen et al. 2016). Recently there has been some more interest in evaluation of the efficiency of fishways and how to facilitate safe two-way migration past dams and weirs (Fjeldstad et al. 2012, Fjeldstad et al. 2018, Holter et al. 2020).</p><p>Throughout the period there has been strong interest in stocking of trout, and numerous studies have focused on the stocking method (Fjellheim et al. 1995, Hesthagen et al. 1995, Finstad and Jonsson 2001, Solås et al. 2019). Stocking and translocation have been common for a long time (Huitfeldt-Kaas 1918, Nilssen 2017), but rarely has management goals been formulated and even more rarely have it been tested if the goals have been met (Vøllestad and Hesthagen 2001). Stocking has been used for different reasons, but most often to increase the potential yield in recreational inland fisheries. Such stocking is being discontinued, and studies on the potential population level effects of stopping stocking should be done (Nater et al. 2022). One effect of stocking that should be evaluated further is the effect of introgression of stocked, non-native trout into wild populations (Wollebaek et al. 2010). The genetic effect on native gene pools by the use of non-native stocked fish has been intensively discussed internationally (Ryman 1981, Ryman and Utter 1987, Ryman and Laikre 1991, Araki et al. 2007).</p><p>A recent problem for trout is the interaction with the aquaculture industry. The main problem is the interaction between anadromous trout and the sea lice (Vollset et al. 2017, Vollset et al. 2018, Serra-Llinares et al. 2020). Overall, this interaction between sea trout and the Atlantic salmon farming industry has also led to some more studies on the marine phase of the life cycle of the trout. However, were little if any information is published on the harvesting of sea trout at sea. Almost all studies on management-related issues are from fresh water.</p><p>Overall, the brown trout has been extensively studied – with a variety of topics being handled. The biology of trout is thus in general well understood. However, the marine (coastal) part of the life cycle is less well understood (Thorstad et al. 2016, L’Abee-Lund and Vøllestad 2018). Fortunately, this seems to be changing (Davidsen et al. 2014, Jensen et al. 2014, Flaten et al. 2016, Eldøy et al. 2021).</p></div>	https://treatment.plazi.org/id/371087DDA257FFEBFC823E29FA80FBB8	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA256FFE8FC833809FC35FDBB.text	371087DDA256FFE8FC833809FC35FDBB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Salvelinus alpinus (Linnaeus 1758)	<div><p>Arctic char Salvelinus alpinus (Linnaeus, 1758)</p><p>A total of 318 articles presenting relevant data on Arctic char (char hereafter) were retrieved. The char is distributed throughout most of the country, with anadromous populations in the northern parts. It is also the only freshwater species that has populations on Svalbard and Bjørnøya (Bear Island) (Gulseth and Nilssen 2001, Bytingsvik et al. 2015). Other species have been recorded from freshwater at Svalbard (Svenning et al. 2015), but it seems that only the char has well-established populations.</p><p>The char exhibits extreme variability in life history, behaviour and demography (Klemetsen 2010). This variability has by some been called the “char problem” (Nordeng 1983). Numerous articles describe phenotypic and life history variation in the char, many focusing on the existence of alternative morphs or ecotypes within watercourses. The number of morphs within a system may vary from one (called “normal” char) to the newly discovered four-morph system in Tinnsjøen (Østbye et al. 2020). The system in Tinnsjøen is kind of similar to the well-studied char-system in the Icelandic lake Thingvallavatn (Sandlund et al. 1992). In some river systems in the north, the char can be classified into three different morphs (one anadromous, and two resident morphs) (Nordeng 1983). Some sympatric morphs may be part of the same population, whereas other morphs are more or less reproductively isolated (Hindar and Jonsson 1993, Praebel et al. 2016). This leads to a classic discussion about the importance of genetic differentiation and phenotypic plasticity (Nyman 1972, Hindar et al. 1986, Whiteley et al. 2019). For example, some researchers have classified selected populations from Norwegian lakes as separate species (Kottelat and Freyhof 2007). Understanding the structuring of char seems particularly difficult. But it is also a common topic of discussion regarding other species that have invaded lakes and rivers post-glacially (Bernatchez 2004). It is at times difficult to detect the existence of sympatric populations, and potentially also species, as it may require more sensitive genetic methods than has been in use until recently (Jorde et al. 2018). Clearly, the systematics of the Arctic char is not fully resolved.</p><p>On average, eight articles focusing on the char were published per year during the 40-year period. It was a tendency that number of published papers increased through the period (R 2 = 0.115, slope estimate 0.13 ± 0.05 y-1, P = 0.014), but the among-year variation was large. Most of the retrieved articles could be classified as ecological (76.8 %), whereas behaviour was investigated to a very limited degree (1.9 %). The ecological studies had a wide range of contexts, but many were focusing on the position of the char in the ecosystem. Many have studied the diet of the char, usually in lakes (Dervo et al. 1991, Dahl-Hansen et al. 1994, Gregersen et al. 2006, Amundsen et al. 2008). In that context, numerous studies have also investigated the transmission of various parasites (Knudsen and Klemetsen 1994, Knudsen 1995, Amundsen et al. 2003 b, Siwertsson et al. 2016). A particular observation is that most of these studies are from North-Norway.</p><p>The char is considered to be a very efficient zooplankton predator, and several studies consider the interaction between char and other fish species. In particular, the relationship between char and trout (Saksgård and Hesthagen 2004, Persson et al. 2007, Hesthagen et al. 2011a, Guenard et al. 2012, Persson et al. 2013) has had particular interest. The char have high growth efficiency relative to the trout, but still seem to be out-competed by the trout - in particular in relatively warm and productive lakes (Finstad et al. 2011). Modelling exercises from Sweden indicates that increasing temperatures and interaction with trout may lead to an extensive population loss (Hein et al. 2012). Similar predictions have been made from other locations in Europe (Kelly et al. 2020). No such studies are available from Norway yet. The char may also be at peril due to the increasing distribution of the pike (Hein et al. 2012).</p><p>Overall, the feeding biology of the char is well understood as also seems the case with variation in life history (Nordeng 1983, Vøllestad and L’Abée-Lund 1994). Also the anadromous part of the life cycle of char has been investigated – focus has been both on why some individuals or populations are migratory (Finstad and Hein 2012), and the migration process itself (Berg and Berg 1989, Finstad and Heggberget 1995). Even if the ecology of the char is relatively well understood, the drivers of the extensive phenotypic variation are still in need of understanding. In order to acquire such understanding evolutionary questions has to be asked.</p><p>In total only 29 papers with an evolutionary focus were found by the search. Some small-scale population genetic studies were found (Hindar et al. 1986, Westgaard et al. 2004, Wollebaek et al. 2011, Praebel et al. 2016, Østbye et al. 2020). However, the number of studies were very small relative to the large phenotypic variability that can be found. More classic evolutionary studies focussed on various aspects of sexual selection (Skarstein and Folstad 1996, Skarstein et al. 2005, Egeland et al. 2015), and also some more functional genetics studies were found (Eliassen et al. 1998, Lysfjord and Staurnes 1998).</p><p>A relatively limited number of papers (n = 15) handled the effects of pollution. As expected, some papers focused on the effect of acidification of surface waters (Andersen et al. 1984, Hesthagen and Sandlund 1995), while some also followed the effects of the Chernobyl accident (Forseth et al. 1998, Jonsson et al. 1999). Otherwise, few if any studies focused on other kinds of pollutants and their effect on individuals or populations. Thus, even if the number of papers published on the char is relatively large (n = 318), the number of studies with a direct management application is limited. There are some studies focussing on the effect of harvesting (or different ways of harvesting) (Langeland 1986, Finstad et al. 2000, Smalås et al. 2020), and there are some studies focusing of the potential for the char to be a temporary host for parasites such as Gyrodactylus salaris (Bakke et al. 1996, Robertsen et al. 2007, Winger et al. 2008b). Recently, there has also been some studies on the effect of sea lice infections of sea-run char (Bjørn et al. 2001, Bjørn and Finstad 2002). However, the number of such studies are small relatively to those published on Atlantic salmon and sea trout. Overall, even if the ecology of char is well-understood, there clearly is a wide range of topics that needs better understanding. The important drivers of phenotypic variability are not understood, as well as the importance of genetic differentiation and level of response to natural selection (potentially leading to local adaptation).</p></div>	https://treatment.plazi.org/id/371087DDA256FFE8FC833809FC35FDBB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA255FFE9FC833E09FE0EFDBB.text	371087DDA255FFE9FC833E09FE0EFDBB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Coregonus lavaretus (Linnaeus 1758)	<div><p>Whitefish Coregonus lavaretus (Linnaeus, 1758)</p><p>The whitefish is one of the most phenotypically variable freshwater fishes, in Norway and globally. This has led to large controversy regarding number and naming of species (Kottelat and Freyhof 2007). For example, in Sweden different authors have suggested the presence of many different species (see summary by Svärdson 1998). Gunnar Svärdson published during several decades numerous papers in a series he called “the coregonid problem”. And clearly the taxonomy and systematics is still a mess. Today, the SLU Swedish Species Information Center recognizes one species of whitefish, Coregonus maraena (Bloch, 1779), with four taxa that are classified as morphotypes. In Norway, the Norwegian Biodiversity Information Centre recognized only one species, C. lavaretus . Also, in Finland the whitefish is classified as C. lavaretus by the Finnish Biodiversity Info Facility. Clearly, this is a situation that should be sorted out – as the whitefish clearly has a continuous distribution in Scandinavia.</p><p>One reason for the taxonomic confusion is the large phenotypic variability and also flexibility in use of spawning and feeding habitat. In Norway this has led to the presence of numerous reproductively isolated sympatric populations in many lakes. Many studies have focused on trying to describe this variability, using both classic ecological and population genetic methods (Østbye et al. 2005, Østbye et al. 2006, Siwertsson et al. 2013, Bitz-Thorsen et al. 2020). Most of these studies are from North-Norway or from the lake Femunden in mid-Norway. Clearly, there is still a need for more studies, from different geographic regions, in order to understand the origin and drivers of the genetic and phenotypic variation in sympatric whitefish populations. More extensive genomic tools are probably needed, such as full-genome sequencing using next-generation sequencing tools. An example of this is the detailed studies of a whitefish radiation in alpine European lakes (Vonlanthen et al. 2012, Frei et al. 2022). However, also here it can be discussed if the taxa studied are species, or populations of the same species.</p><p>One interesting topic that has been studied recently is on how various whitefish morphs/phenotypes are differentially impacted by the invasion of other species. In particular the effect of the invasion of vendace C. albula to Pasvik has led to the dramatic reduction in the abundance of the small-sized plankton-feeding morph (Bøhn et al. 2004, Bøhn et al. 2008). Clearly, the existence of different morphs of whitefish in a lake is contingent on ecological opportunity driven by habitat availability and presence of competitors and predators. Whitefish may have a very diverse ecological niche, and may therefore also impact on other freshwater species. This potential interactions with other species have also been investigated to some degree, in particular the interaction with Arctic char has received some interest (Amundsen et al. 2010, Eloranta et al. 2011, Sandlund et al. 2016a).</p><p>The whitefish has been repeatedly translocated in Norway, and it is unclear what is a naturally recruited population or what is due to human translocation (Sandlund et al. 2013b, c). It would be interesting to use modern genetic methods to try to investigate this. This should be possible as more and more high quality genomes are published, also for various Coregonus species (Merot et al. 2022).</p><p>On average, more than two papers focusing on whitefish biology has been published per year, and the publication rate has been stable throughout the time period investigated (slope estimate 0.03±0.02 year-1). Overall, the biology should be well understood, but given the phenotypic and genetic diversity present a full understanding is eluding us. In a biodiversity context, a complete understanding as well as a Scandinavian agreement on the taxonomic status of the different populations/morphs is needed.</p></div>	https://treatment.plazi.org/id/371087DDA255FFE9FC833E09FE0EFDBB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA254FFE9FF203E09FDA7F9F8.text	371087DDA254FFE9FF203E09FDA7F9F8.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Coregonus albula (Linnaeus 1758)	<div><p>Vendace Coregonus albula (Linnaeus, 1758)</p><p>Vendace was investigated in a total of 49 papers over the 40-year time period investigate. On average a little over one paper has been published per year, and there was no temporal trend in the publication rate (slope estimate 0.02 ± 0.02 year-1). The vendace has a limited distribution in Norway, with its main distribution along the border to Sweden in the south-eastern part of the country. Previous stocking efforts have, however, also led to the species being distributed outside its natural distribution area (Sandlund et al. 2013b).</p><p>The introduction of the vendace to the Pasvik river system in North-Norway has raised particular interest (Amundsen et al. 1999). The focus has been on how the introduction of this efficient zooplankton predator has led to changes in the ecosystem, and in particular how it has impacted the dynamics of the polymorphic whitefish (Bøhn and Amundsen 2001, Bøhn et al. 2008). Almost half of the publications on vendace were on various topics related to the invasion into the Pasvik system. All of these papers are from the 1990s onwards. This means that almost all articles on the vendace during the last 20 years are from the Pasvik system, and mainly focussing on the ecosystem effects of the invasion of vendace into this river system. Based on these observations the vendace is classified as a regionally invasive species with low risk (Artsdatabanken 2018).</p><p>Clearly, a lot has been learnt on the trophic ecology of the vendace, and how this species interacts with different parts of the food web in arctic systems. But the strong geographic bias also indicates that little effort has been invested into understanding the ecological function of vendace in more southern and biologically complex systems. Even in the lake Mjøsa, where there earlier was a famous fishery for vendace (or lågåsild as it is locally known) (Huitfeldt-Kaas 1917, Aass 1972), very little recent work has been published (Naesje et al. 1986, Naesje et al. 1991, Gregersen et al. 2011). This is unfortunate, as this and other comparable lakes have experienced large environmental changes during the last decades (Moe et al. 2022).</p></div>	https://treatment.plazi.org/id/371087DDA254FFE9FF203E09FDA7F9F8	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA254FFE9FC8238A9FC73F8FB.text	371087DDA254FFE9FC8238A9FC73F8FB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Lotidae Bonaparte 1835	<div><p>Lotidae</p><p>The family Lotidae have earlier been classified as a sub-family under the Gadidae . The family contains only five species in total and one species, the burbot Lota lota (Linnaeus, 1758), is found in freshwater in Norway. The burbot is mainly distributed in southeast and north in Norway, but with a few populations in mid-Norway (Huitfeldt-Kaas 1918, Hesthagen et al. 2021c).</p><p>Only 17 articles were retrieved by the search, indicating that very little research has focussed on the burbot. In many of the articles the burbot was not the primary species of interest, rather if was a minor part of investigations of the food web (Amundsen et al. 2003a, Sandlund et al. 2013a). Very few studies focussed on the biology of the burbot (Sandlund et al. 1985, Vøllestad 1992). On the other side, some articles have studied the effects of pollution (Frøslie et al. 1985, Mariussen et al. 2008, Berg et al. 2013). However, these studies are mainly from lake Mjøsa.</p><p>In total, the knowledge about the biology of burbot in Norway is very limited. There are no studies available on the reproduction, migration, spawning behaviour or population dynamics of the species. This is unfortunate, as the burbot may be an important part of the benthic ecosystem in many lakes and large rivers. It is also an important predator.</p></div>	https://treatment.plazi.org/id/371087DDA254FFE9FC8238A9FC73F8FB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA254FFE9FF213A49FAAFFBDB.text	371087DDA254FFE9FF213A49FAAFFBDB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Thymallus thymallus (Linnaeus 1758)	<div><p>Grayling Thymallus thymallus (Linnaeus, 1758)</p><p>The grayling is distributed in the south-eastern and the far northern part of Norway, and is usually considered to be a purely riverliving species (Huitfeldt-Kaas 1918). However, it is also found in numerous lakes, including the largest Norwegian lake – Mjøsa (Huitfeldt-Kaas 1917). Phylogeographic studies have shown that two different evolutionary lineages have immigrated into Norway following deglaciation (Koskinen et al. 2000), however this has not been followed up by more detailed studies.</p><p>A total of 37 articles were retrieved by the literature search, most of which (almost all) were based on studies from the Glomma riversystem in the south-eastern part of Norway. Glomma is the largest river in Norway, splitting into two main upstream branches; Glomma and Gudbrandsdalslågen. In the upper part of Gudbrandsdalslågen the introduced grayling has been intensively studied during over 30 years. Most of these studies are initiated from the University of Oslo (Vøllestad and Primmer 2019). These studies originally focussed on classical ecological topics (Haugen and Rygg 1996b, Haugen 2000a), but later focussed on evolutionary processes including population genetics (Barson et al. 2006, Junge et al. 2011) and adaptation to differential temperatures (Haugen 2000 a, b, Kavanagh et al. 2010, Mäkinen et al. 2016). Lately it has led to genomic studies of different types (Papakostas et al. 2010, Papakostas et al. 2014, Mäkinen et al. 2018). For example, the annotated genome of grayling was published recently (Varadharajan et al. 2018, Sävilammi et al. 2019), facilitating even more detailed evolutionary studies. Most of these studies are based on grayling in the upper reaches and high-altitude systems. Further downstream in the two rivers and the lake Mjøsa detailed studies with applied focus on the population structure, dispersal, and the effect of lack of connectivity has been performed (Linløkken 1993, Kristiansen and Døving 1996, Heggenes et al. 2006, van Leeuwen et al. 2016, van Leeuwen et al. 2018, Holter et al. 2020). All these studies have increased our understanding of grayling life history. However, there is still only limited knowledge about feeding (Haugen and Rygg 1996 a, Amundsen et al. 2010) and parasitism (Mo et al. 1998, Ieshko et al. 2001), etc. The grayling is host to the monogenean parasite Gyrodactylus thymalli Zitnan, 1960, and this parasite is of great interest as it is very similar to the pathogenic G. salaris (Fromm et al. 2014, Mieszkowska et al. 2018). Some work has been done on the biology of G. thymalli (Pettersen et al. 2015, Pettersen et al. 2021), but clearly more work should be done.</p><p>The biology of the grayling is relatively well known, but the information is geographically biased towards one particular river system. And there are no studies focusing on population dynamics or on how grayling populations might vary over time.</p></div>	https://treatment.plazi.org/id/371087DDA254FFE9FF213A49FAAFFBDB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA254FFEEFC833B49FED8F99B.text	371087DDA254FFEEFC833B49FED8F99B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Gasterosteidae Bonaparte 1831	<div><p>Gasterosteidae</p><p>Two species of stickelbacks are native in Norwegian freshwater. Both species can also be found in both brackish and marine waters. In particular the three-spined stickleback Gasterosteus aculeatus Linnaeus, 1758 in common throughout coastal waters as well as marine waters along the Norwegian coast (Huitfeldt-Kaas 1918, Klepaker 1996). The nine-spined stickleback Pungitius pungitius (Linnaeus, 1758) has a more limited distribution. Sticklebacks are intensively studies globally, in particular the three-spined stickleback is used as a model species in a wide range of research fields (Östlund-Nilsson et al. 2007, Wootton 2009). The nine-spined stickleback has gotten less interest. This is also clear in Norway, where only five articles were retrieved by the search. Only one of the studies focussed on the nine-spined stickleback in some detail (Klepaker et al. 2013). Two studies focussed on parasites, but mainly in the three-spined stickleback (Rødland 1983, Soleng and Bakke 1998). Overall, we know almost nothing about the biology of the nine-spined stickleback in Norwegian ecosystems. This is in stark contrast to the three-spined stickleback, where we retrieved 49 articles by the search.</p><p>Many of the studies on three-spined stickleback focussed on the phenotypic variation observed in lateral bony plates – a trait that is extensively studied in this species. These studies concerned the large-scale (Klepaker 1995, 1996, Voje et al. 2013) and small-scale distribution (Le Rouzic et al. 2011, Østbye et al. 2016, Østbye et al. 2018) of the plate morphs among and within ecosystems, and how it differs depending on various selective processes (Myhre and Klepaker 2009, Bjaerke et al. 2010, Mazzarella et al. 2015). These studies also included the use of modern genetic/genomic methods (Taugbøl et al. 2014, Mazzarella et al. 2016). Also, the other main anti-predator defence system – the dorsal and pelvic spines – have been studied (Klepaker et al. 2012, Klepaker et al. 2013). These studies in general are set in an evolutionary context.</p><p>The three-spined stickleback is an important prey fish for many freshwater fishes, and several studies have investigated such predator-prey relationships (Jakobsen et al. 1988, L’Abée-Lund et al. 1992, Amundsen 1994). In an ecosystem context, distribution, transmission and importance of various parasites has also been studied in some detail (Amundsen et al. 2013, Braicovich et al. 2016, Kuhn et al. 2016). This has also been studied in the context of sexual selection and spawning behaviour (Folstad et al. 1994). In addition to this parasite focus, several studies have used three-spined stickleback to study toxic effects of various compounds (Wibe et al. 2002, Knag and Taugbøl 2013).</p><p>Even if the tree-spined stickleback has been studied in some detail, little is known about its population dynamics and ecosystem effects. This is unfortunate, in particular based on reports from the brackish Baltic Sea where changes in the stickleback density have had strong effects on numerous other species (Bergström et al. 2015, Byström et al. 2015, Eklöf et al. 2020). This lack of basic biological information is shared by many other small-sized fish species – both in freshwater and in the sea.</p></div>	https://treatment.plazi.org/id/371087DDA254FFEEFC833B49FED8F99B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA253FFEEFF213A69FA28FCFB.text	371087DDA253FFEEFF213A69FA28FCFB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Cottidae Bonaparte 1831	<div><p>Cottidae</p><p>In total three species of sculpins are found in Norwegian freshwaters (Table 1). Only the alpine bullhead Cottus poecilopus Haeckel, 1835 is distributed over a larger geographic area. The other species, bullhead C. gobio Linnaeus, 1758 and fourhorn sculpin have very limited natural distribution.</p><p>I found no publication on the fourhorn sculpin during the time period investigated. This species is only observed in two large lakes, Mjøsa and Store Le, but there is almost no information about population size or biology. The species has also been listed on the Norwegian Red List both in 2010 (VU) and 2015 (DD). However, it was removed from the list in 2021 (Hesthagen et al. 2021b). Even if no articles were recovered by the formal search, there are a few Norwegian reports available.</p><p>The bullhead is also a species with very limited distribution in Norway. However, it has relatively recently been found in new locations and may be spreading (Frilund et al. 2009). The limited natural distribution led to a listing as Near Threatened on the 2006 Red List; it was subsequently removed from the list. There is, however, almost no knowledge about this species in Norway.</p><p>The biology of the alpine bullhead, on the other hand, has been studied to some degree. In particular it has been studied how it might interact with sympatric species such as trout (Holmen et al. 2003, Hesthagen et al. 2004, Hesthagen et al. 2011a) and Atlantic salmon (Gabler and Amundsen 1999, Gabler and Amundsen 2010, Sanchez-Hernandez et al. 2016). The studies of the interaction with Atlantic salmon were initiated because the alpine bullhead had invaded a salmon river (River Tana/Teno with tributaries), producing a need to know more about how bullhead and other species may engage in competitive interactions. Following this, there has also been some studies on how the alpine bullhead may be a vector for important parasites such as Gyrodactylus salaris (Winger et al. 2008a, Bakke et al. 2019).</p><p>In general, there is very little knowledge about population biology (dynamics, structure) and ecology of the three sculpin species under Norwegian conditions. This lack of knowledge is shared with a number of other small-sized species with little economic interest.</p></div>	https://treatment.plazi.org/id/371087DDA253FFEEFF213A69FA28FCFB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA253FFEFFC833F49FDDBFDF8.text	371087DDA253FFEFFC833F49FDDBFDF8.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Percidae Rafinesque 1815	<div><p>Percidae</p><p>Three species of percids are found in Norway, but only the Eurasian perch Perca fluviatilis Linnaeus, 1758 is common over large areas. The perch is common both in North-Norway and in the south-eastern part of the country and is considered as one of the most common freshwater fishes in the country (Huitfeldt-Kaas 1918). Being common, and also of interest for recreational fishers, there has been considerable interest in this species by researchers. In total 55 articles were retrieved by the search, indicating that more the one article has been published per year in the period investigated.</p><p>The perch is a cold-water adapted fish that spawn early in spring. Being cold-adapted the perch was one of the first non-anadromous freshwater species that invaded Norway after the last glaciation. It is also one of the few Norwegian freshwater fish species where the immigration routes and phylogeography has been investigated in some detail (Refseth et al. 1998, Nesbø et al. 1999). These studies indicated that perch in southeast Norway probably belong to two different evolutionary lineages that penetrated into Norway via either a southern route (along the coast in the cold meltwater) or from the east through the Baltic Sea and through the large Swedish watercourses. If was postulated that these immigration routes probably have been used by other freshwater fishes also. Unfortunately, this has not been followed up using more up-to-date genetic methods.</p><p>Many studies on the perch have otherwise focussed on general population ecology (Heibo and Vøllestad 2002, Heibo et al. 2005, Linløkken and Haugen 2006), including studies of food webs (Amundsen et al. 2003a, Sharma and Borgstrøm 2008b, Linløkken and Hesthagen 2011). In relation to these food-web related studies there has been numerous studies on the accumulation of various pollutants (mercury, DDT, PCB, etc) (Frøslie et al. 1985, Brevik et al. 1996, Amundsen et al. 1997, Okelsrud et al. 2016).</p><p>The perch is distribution in areas that was heavily impacted by acidification. Thus, several studies focussed on the effects and potential recovery following the reduction in acidification (Hesthagen et al. 1993, Øxnevad et al. 1995, Saksgård and Hesthagen 1995, Østbye et al. 1997, Poléo et al. 1997). Clearly, the various studies that has been performed on perch has produced a general understanding of the ecology of this species. The perch also seems very resilient towards various ecological stressors. However, as evidenced by what is happening in the Baltic Sea where perch and pike has been reduced drastically during recent years (Bergström et al. 2015, Eklöf et al. 2020), we need to keep an eye also on this species.</p><p>The two other percid species (ruffe Gymnocephalus cernuus (Linnaeus, 1758) and pikeperch Sander lucioperca (Linnaeus, 1758)) have a very limited distribution in the south-eastern part of Norway, and only a very few studies were found focussing on these species (Table 1). Actually, the retrieved studies only rarely focussed on the ecology of these two species (Brabrand 1983, Vøllestad 1985, Kålås 1995, Hesthagen et al. 2012), and they were mostly published in Norwegian. This lack of focussed studies on these species are unfortunate, as they tend to be important parts of the food-web in lakes where they occur (Brabrand and Faafeng 1993).</p></div>	https://treatment.plazi.org/id/371087DDA253FFEFFC833F49FDDBFDF8	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
371087DDA252FFEFFF203E49FF40FC3B.text	371087DDA252FFEFFF203E49FF40FC3B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Centrarchidae Bleeker 1859	<div><p>Centrarchidae</p><p>Fish belonging to the family Centrarchidae is native to North America, and thus the species found in Norway (pumpkinseed Lepomis gibbosus (Linnaeus, 1758)) is a recent introduction (Sterud and Jørgensen 2006). The species has a very limited distribution, and is expected to have a limited ecological impact (Hesthagen and Sandlund 2007). However, there is basically no available knowledge about its ecology and potential interaction with other parts of the local food webs.</p></div>	https://treatment.plazi.org/id/371087DDA252FFEFFF203E49FF40FC3B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Vøllestad, Leif Asbjørn	Vøllestad, Leif Asbjørn (2023): A paradoxical bias in knowledge about Norwegian freshwater fishes: research efforts during 1980 - 2020. Fauna norvegica 42: 6-30, DOI: 10.5324/fn.v42i0.4965, URL: https://doi.org/10.5324/fn.v42i0.4965
