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Anadromous Arctic charr Salvelinus alpinus is a cold-adapted salmonid that is vulnerable to climate warming and anthropogenic activities including salmon farming, hydropower regulation, and pollution, which poses a multiple-stressor scenario that influences or threatens populations. We studied the horizontal and vertical behaviour of Arctic charr tagged with acoustic transmitters (n = 45, mean fish length: 22 cm) in a pristine, subarctic marine area to provide insights into the behaviour of first-time migrants. Tagged fish spent up to 78 d at sea, with high marine survival (82% returned to their native watercourse). While at sea, they utilized mostly near-shore areas, up to 45 km away from their native river. Arctic charr showed large variation in migration distance (mean ± SD: 222 ± 174 km), and the migration distance increased with body size. Although the fish displayed a strong fidelity to surface waters (0-3 m), spatiotemporal variation in depth use was evident, with fish utilizing deeper depths during the day and in late July. These results represent baseline data on Arctic charr’s marine behaviour in a pristine fjord system and highlight the importance of near-shore surface water as feeding areas for first-time migrants. Furthermore, the observed dependency on coastal areas implies a vulnerability to increasing human-induced perturbations, on top of impacts by large-scale climate change in marine and freshwater habitats.

While populations of other migratory salmonids suffer in the Anthropocene, pink salmon (Oncorhynchus gorbusca Salmonidae) are thriving, and their distribution is expanding both within their natural range and in the Atlantic and Arctic following introduction of the species to the White Sea in the 1950s. Pink salmon are now rapidly spreading in Europe and even across the ocean to North America. Large numbers of pink salmon breed in Norwegian rivers and small numbers of individuals have been captured throughout the North Atlantic since 2017. Although little is known about the biology and ecology of the pink salmon in its novel distribution, the impacts of the species' introduction are potentially highly significant for native species and watershed productivity. Contrasts between pink salmon in the native and extended ranges will be key to navigating management strategies for Atlantic nations where the pink salmon is entrenching itself among the fish fauna, posing potential threats to native fish communities. One key conclusion of this paper is that the species' heritable traits are rapidly selected and drive local adaptation and evolution. Within the Atlantic region, this may facilitate further establishment and spread. The invasion of pink salmon in the Atlantic basin is ultimately a massive ecological experiment and one of the first examples of a major faunal change in the North Atlantic Ocean that is already undergoing rapid changes due to other anthropogenic stressors. New research is urgently needed to understand the role and potential future impacts of pink salmon in Atlantic ecosystems. Atlantification, biological invasions, climate adaptation, Pacific Ocean, regime shift

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Source at https://vkm.no/risikovurderinger/allevurderinger/karplantersomikkeerstedegnevurderingavfolgerforbiologiskmangfold.4.396ddfe21729324f51a2b2e8.html We sow or plant vascular plant species on a large scale in revegetation and restoration projects in Norway today. Some of the species used are already found in Norway, but many of the species, subspecies or populations used though native are not local, that is, they are regionally alien. A regionally alien species is a species that is native to Norway (has been in Norway since 1800) somewhere in the country, but which has been spread by humans to places in Norway where they do not occur. In theory, and according to the Biodiversity Act, it is desirable to use local seeds or plants to preserve local biodiversity.

Source at https://vkm.no/ The Norwegian Scientific Committee for Food and Environment (VKM) was requested by the Norwegian Environment Agency to assess the risk of negative impacts to biodiversity in Norway resulting from import of crustacean decapods for keeping in freshwater aquariums. VKM was asked to 1) list species of crayfish, crabs and shrimps that are currently kept in freshwater aquaria in Norway, and species that are likely to be kept in freshwater aquaria in Norway within the next 10 years, 2) assess the ability of the species to survive under Norwegian conditions and cause impacts on ecosystems and other species, and 3) state the potential negative effects on the biological diversity of diseases caused by pathogens, regulated under the Norwegian Food Act.

The aim of this report is to define guidelines that helps prevent the planting of vascular plant species with a high potential for negative effects on local biodiversity. It is assumed that the native or local populations are better adapted to local environmental conditions than populations from other areas or regions, and the risk of harmful genetic changes is therefore considered small when using local plant and seed sources. Arriving at a common definition for the area within which plants are “local” is difficult, though; vascular plant species are numerous (3317 species in mainland Norway, of which more than half are alien species introduced after 1800, Artdatabanken 2015), have different growth forms, different environmental requirements, and different reproductive and dispersal ecology. Even closely related vascular plant species can differ in such characteristics and hence in the extent of the "place" or “area”. publishedVersion

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We sow or plant vascular plant species on a large scale in revegetation and restoration projects in Norway today. Some of the species used are already found in Norway, but many of the species, subspecies or populations used though native are not local, that is, they are regionally alien. A regionally alien species is a species that is native to Norway (has been in Norway since 1800) somewhere in the country, but which has been spread by humans to places in Norway where they do not occur. In theory, and according to the Biodiversity Act, it is desirable to use local seeds or plants to preserve local biodiversity. The aim of this report is to define guidelines that helps prevent the planting of vascular plant species with a high potential for negative effects on local biodiversity. It is assumed that the native or local populations are better adapted to local environmental conditions than populations from other areas or regions, and the risk of harmful genetic changes is therefore considered small when using local plant and seed sources. Arriving at a common definition for the area within which plants are “local” is difficult, though; vascular plant species are numerous (3317 species in mainland Norway, of which more than half are alien species introduced after 1800, Artdatabanken 2015), have different growth forms, different environmental requirements, and different reproductive and dispersal ecology. Even closely related vascular plant species can differ in such characteristics and hence in the extent of the "place" or “area”. The dispersal ecology of a plant species is of great importance for whether the species has genetically distinct populations within its range or not. Different strategies (wind pollination vs. insect pollination, vegetative propagation vs. seed dispersal, large seeds vs. small seeds) have an impact on the degree of gene flow between populations and thus also how locally adapted the species is in different areas. Whether the species has primarily vegetative reproduction or whether it spreads mainly by means of seeds, and whether the seed dispersal takes place ballistically, with wind or water, or by zookori (attached to animals or eaten by animals) determines how far the species can spread and how large gene flow there is between different populations. Whether the species is pollinated by wind or by the help of insects also affects the degree of gene flow differently. In Norway, there is great variation in many biophysical and ecological conditions (climate, topography, hydrology, and geology) over relatively short distances. This means that species that grow only a few meters apart can grow under different environmental conditions. This large variation in environmental conditions - on different spatial scales - can give rise to local genetic adaptation. However, plants have been moved around the landscape for several hundred years by our livestock (as seeds in fur and hooves, and in faeces) from lowland pasture to mountain pasture and along traffic arteries across the country due to the extensive transport of animals and people. Over time, this has led to expanded geographical distribution for several species and increased gene flow between populations over relatively large distances. .............

Climate change · Ecological restoration · Gene flow · Genetic diversity · Habitat fragmentation · Inbreeding · Local seeds · Local adaptation · Native seeds · Outbreeding depression · Plant genetic resources · Regional adaptation · Region of origin · Rehabilitation · Revegetation · Seed biology · Seed collection · Seed mixture · Seed provenance · Seed sourcing strategy · Seed transfer zones · Site-specific seeds

Key words: Risk assessment, Crayfish, Shrimps, Crabs, Climate change, Aphanomyces astaci, White spot syndrome, Alien species, Biological invasion Introduction The Norwegian Scientific Committee for Food and Environment (VKM) was requested by the Norwegian Environment Agency to assess the risk of negative impacts to biodiversity in Norway resulting from import of crustacean decapods for keeping in freshwater aquariums. VKM was asked to 1) list species of crayfish, crabs and shrimps that are currently kept in freshwater aquaria in Norway, and species that are likely to be kept in freshwater aquaria in Norway within the next 10 years, 2) assess the ability of the species to survive under Norwegian conditions and cause impacts on ecosystems and other species, and 3) state the potential negative effects on the biological diversity of diseases caused by pathogens, regulated under the Norwegian Food Act. Methods The risk assessment, without focus on pathogens, was performed in two steps. First, we used a pre-screening toolkit to identify species of crayfish, crabs and shrimps with potential to become invasive in freshwater habitats in Norway. Each species was given an invasiveness score based on 55 questions on biogeography, ecology, and climate change. In a second step, a full risk assessment, including the potential impacts of pathogens, was conducted on those species receiving the highest invasiveness score. This assessment included questions on the organism’s probability of entry and pathways of entry, establishment and spread, potential impacts on biodiversity, and how climate change scenarios might affect the assessment. Likelyhood and confidence was assessed for each question. In conclusion, each species was designated as either low-, moderate-, or high risk. Many crustacean decapod species are confirmed or suspected carriers of pathogens that can cause mass mortality among native crustaceans. The risk posed by crustaceans as carriers of pathogens may be independent of the environmental risk that they pose through ecological interactions. Therefore, the four crustacean disease pathogens that are regulated under the Norwegian Food Act, were assessed separately. These include Aphanomyces astaci causing crayfish plague, white spot syndrome virus (WSSV) causing white spot disease, Taura syndrome virus (TSV) causing Taura syndrome, and yellow head virus genotype 1 (YHV1) causing yellow head disease. The assessments comprised questions on the pathogen’s probability of entry (as a hitchhiker organism with imported crustaceans), pathways of entry, establishment and spread, and potential impact on crustacean biodiversity. Likelihood and confidence were assessed for each question. In conclusion, each pathogen was designated as either low-, moderate-, or high risk. In a third step, we categorized the likelihood that a crustacean species introduces a pathogen associated with a high- or moderate risk into: I) known chronic carriers, II) suspected chronic carriers, III) suspected situational carrier, IV) possible pathogen transmitters, and V) no direct or circumstantial evidence for carrier status or pathogen transmission in the genus. Results Based on information from the Norwegian Pet Trade Association, the project group listed 112 taxa (mainly species and some genera) of freshwater crayfish, crabs and shrimps that are relevant for trade in Norway. These included 38 crayfish taxa, 28 crab taxa, and 45 shrimp taxa. In addition, one marine crab was included. Sixteen species of crayfish, four species of shrimps, and two species of crabs underwent a full ecological risk assessment. The probabilities of entry both into the aquarium trade in Norway, and potentially further into Norwegian nature, were based on the prevalence of the species in the aquarium trade in Norway. We assumed that all species were equally likely to escape captivity or to be .........

The Norwegian Environment Agency and the Norwegian Food Safety Authority asked the Norwegian Scientific Committee for Food and Environment to assess the risk to Norwegian biodiversity, to the productivity of native salmonid populations, and to aquaculture, from the spread and establishment of pink salmon in Norwegian rivers, and to assess mitigation measures to prevent the spread and establishment of this alien species. Pink salmon is native to rivers around the northern Pacific Ocean. The species usually has a strict two-year life cycle, with populations spawning in even and odd years being genetically isolated. Fertilized eggs of pink salmon were transferred from Sakhalin Island to Northwest Russia in the late 1950s, and fry were released in rivers draining to the White Sea. The first abundant return to rivers in Northwest Russia, as well as to Norway and other countries in northwestern Europe, was recorded in 1960. Stocking with fish from Sakhalin was terminated in 1979. By then, no self-sustaining populations had been established. From 1985 onwards, stocking in White Sea rivers was resumed with fish from rivers in the more northerly Magadan oblast on the Russian Pacific, resulting in the establishment of reproducing populations. Stocking was continued until 1999, when the last batch of even-year fertilized eggs was imported, and the fry released in spring 2000. Thus, all pink salmon caught after 2001 in the Northeast Atlantic and the Atlantic side of the Arctic Ocean including the Barents Sea, as well as in rivers draining into these seas, are the result of reproduction in the wild. Pink salmon is now established with abundant and increasing stocks in Northwest Russia and regular occurrence in rivers in eastern Finnmark. Catches of odd-year adult pink salmon in Northwest Russia were usually below 100 tonnes before 2001 and increased to an annual average of 220.5 tonnes during the period 2001-2017. Even-year returns are smaller than odd-year returns both in Northwest Russia and in Norway. The number of pink salmon recorded in Norwegian rivers peaked in 2017, with a high number of fish in eastern Finnmark, and substantial numbers recorded in rivers all along the coast of Norway and in other European countries. In 2019, the area with abundant returns expanded in comparison with 2017, to include rivers in western Finnmark and Troms. The recorded numbers were perhaps lower in southern Norway in 2017 than in 2019 (full statistics not available when this report was finalised), but also in southern Norway there were more pink salmon in 2019 than in any year before 2017. The large numbers of pink salmon in western Finnmark and Troms in 2019 may indicate an expansion of the area in Norway with abundant odd-year pink salmon returns. In some small rivers in eastern Finnmark, between 1000 and 1500 pink salmon were fished out by local people in 2019, demonstrating the magnitude of the potential impact in terms of numbers of pink salmon. We cannot rule out that this will not happen over larger parts of Norway in the coming years. The even-year strain of pink salmon only occurs in low numbers in Russian rivers, as well as Norwegian, rivers. Adult pink salmon enter the rivers from early July, and spawning occurs in August-September. Spawning habitat requirements are like those of native salmonids: Atlantic salmon, brown trout, and Arctic charr. Spawning of pink salmon occurs earlier than the native salmonids, but observations in 2019 indicate a possible overlap with native salmonids in September in northern Norway. Pink salmon eggs hatch in late winter or spring, and the alevins remain in the gravel until most of the yolk sac has been resorbed. Emerging fry are approximately 30 mm in length. Functionally, they are smolt already at this stage, with a silvery colouration and saltwater tolerance. The fry/smolt start feeding on small invertebrates in some rivers, while the fry/smolt migrate without feeding in other rivers. They impact juveniles of native salmonids through competition for food and space and the invertebrate fauna through predation. The impact depends on the duration of their stay. This is assumed to be very short, but some observations indicate that fry/smolt that emerge from spawning redds far upstream may feed and grow to 60-70 mm before entering the sea. Pink salmon smolt may spend some time in estuaries and coastal waters before moving to the open sea. The next approximately 12 months are spent feeding in the open seas before returning to the coast to seek rivers for spawning. Homing is less precise in pink salmon than in other anadromous salmonids. All spawners die shortly after spawning. Methods This risk assessment is based on an extensive literature search, contact with scientists in North America, western Europe, Russia, Norway, the county governor in Troms and Finnmark, and local anglers’ associations, and other stakeholders in Norway. We have investigated whether ocean temperatures play an important role in the variation of pink salmon year class abundance, and whether the annual abundance of adult pink salmon is increasing with rising sea temperatures. This is an important aspect of a risk assessment in a 50-yr perspective. We have used a semi-quantitative risk assessment. The overall risk is the product of the magnitude of the consequences of the event and the likelihood that the event will occur, as judged by the project group experts. The level of confidence in the risk assessment is described, and uncertainties and data gaps identified. Results The dynamics and environmental impact of introduced pink salmon in Norwegian rivers, coastal waters, and the ocean, depend on their abundance. In all habitats and for all life stages, high abundance may have serious repercussions, whereas low numbers may be of little consequence. An increasing abundance of reproducing pink salmon will likely present hazards to biodiversity and river ecosystems. Establishment of reproducing pink salmon over larger areas in Norway will probably increase the regularity of abundant returns to Norwegian waters. The invertebrate fauna will be negatively affected where large numbers of pink salmon juveniles use it as a food source. This is more likely in long than in short rivers. The river pearl mussel, Margaritifera margaritifera, may be particularly vulnerable, as it has a larval stage in juvenile Atlantic salmon or brown trout, but cannot use pink salmon as a host. Pathogens that may be affected by the increased occurrence of pink salmon in Norway include viruses, bacteria, and parasites (eukaryotic organisms). Very little is known about the susceptibility of pink salmon to viral pathogens. Among 11 viral pathogens assessed, only three or four are known to infect pink salmon. The project group assesses that the potential impact for aquaculture is moderate if infectious haematopoietic necrosis virus is spread by pink salmon in the marine ecosystems. Salmonid alphavirus (SAV)-infected pink salmon, potentially infected through contact with Atlantic salmon aquaculture, moving from south to north could introduce a risk of spread of this virus and the resulting pancreas disease. The project group assesses that the overall potential impact of SAV for aquaculture in the marine ecosystems is low with medium to low confidence. The project group assesses that the potential impacts for aquaculture if Renibacterium salmoninarum and Piscirickettsia salmonis are spread by pink salmon in the marine ecosystems are moderate with low confidence. The potential negative impact on biodiversity in the marine ecosystems and productivity of native salmonid species is assessed as low to minimal for all viral and bacterial pathogens considered, apart from for Renibacterium salmoninarum and viral haemorrhagic septicaemia virus for which the risks were assessed as moderate. Parasites can potentially represent a major hazard to both wild and farmed salmonids, and we have considered three groups of parasites; (1) those that may impact the health and welfare of native salmonids (in the wild and in aquaculture), (2) zoonotic parasites, and (3) aquatic organisms that have a parasitic stage in their life cycle, but are of relevance and interest in Norwegian ecosystems. The abundance and spread of some of these parasites may be affected by the incursion of pink salmon. Hybridization between pink salmon (genus Oncorhynchus) and native salmonids (genera Salmo and Salvelinus) has not been documented in the wild. In the laboratory, intergeneric hybridizations between these species have produced only sterile offspring. Interactions with native salmonids may occur in two ways: through competition for food or through competition for space in the river before spawning and on the spawning grounds. If feeding in the river, pink salmon fry ingest the same prey as native salmonid fry. Thus, competition for food and space may occur if there are high densities of pink salmon for a substantial period. High densities of pink salmon fry may also influence the ability of native salmonid fry to establish territories. On the other hand, emerging pink salmon fry may serve as food for older life stages of native salmonids. Competition for spawning grounds may be restricted due to pink salmon spawning earlier in the autumn. However, there may be temporal overlap between Arctic charr and pink salmon spawning in northern Norway, and a possible overlap in both time and space with early-spawning brown trout. High numbers of pink salmon spawners may have a crowding effect on native salmonids before the actual spawning time. Agonistic behaviour, like chasing of up-migrating Atlantic salmon and brown trout by pink salmon, is known to occur. The effect of this aggressive behaviour on the spawning success of native salmonids is not known. Pink salmon spawners transport organic matter and nutrients from the sea to the rivers. Water quality will be influenced by pink salmon carcasses in rivers after spawning. Decomposition of dead spawners will release organic matter and nutrients (phosphorous and nitrogen) into the water. In nutrient-poor rivers, this will enhance production of algae and zoobenthos, and likely benefit juvenile native salmonids. The impact will likely be negative in more nutrient-rich rivers. Any effect from nutrient input on water quality is likely governed by the number of dead fish, river morphology, and the current nutrient status of the river. Dead and decomposing spawners benefit scavengers of all types and may therefore also affect terrestrial food webs and biodiversity. In the coastal and marine systems, juvenile and adult pink salmon will constitute a new and additional prey for many predators. Pink salmon in the seas may feed on similar prey as native salmonids, and high densities of pink salmon may negatively affect native salmonids as well as the marine ecosystem, as seen in the North Pacific Ocean. Hazards for the aquaculture industry are mainly associated with spreading of disease-causing pathogens. This is directly related to the number of pink salmon in the waters around aquaculture installations. The higher the number of pink salmon, the higher is the probability of individuals carrying pathogens that may be transferred to aquaculture fish. If pink salmon come to dominate the number of salmonids in rivers, this will negatively affect both the economic value of salmon angling, and the value in terms of an important ecosystem service, as catches may be dominated by 1.5 kg fish (that are not fit for human consumption, except early in the season) compared with the larger Atlantic salmon. Under present climatic conditions, pink salmon may spawn and produce offspring in all rivers along the Norwegian coast. Regular occurrence of the odd-year strain has so far only been seen in rivers in eastern Finnmark, where we believe self-sustaining populations have been established. The change from 2017 to 2019 may indicate that the area with rivers receiving high numbers is expanding westwards and southwards into Troms. Establishment of self-sustaining populations depend, in general, on a suffiently high survival of offspring after hatching and when they leave the rivers, and during the marine phase. Abundant returns of pink salmon are correlated with ocean surface temperatures in the North Atlantic Ocean and Barents Sea. Using sea-surface temperature data from 1900 to 2019, we find that the number of pink salmon returning can be relatively well predicted (adjusted R2 > 0.5 for a positive relationship) by sea-surface temperature in the area south of Svalbard and of the cohort size two years previously for all three data sets considered. Hence, the increasing sea surface temperatures and reduced ice cover over the last 20 years may benefit pink salmon in the ocean and be one reason for the increasing number of pink salmon in Northwest Russian and Norwegian waters. However, the average surface temperature of the Arctic Ocean seems to be increasing so rapidly at present that the ecosystem is probably in flux. The effects of this rapid change are unpredictable; however, it is likely that a climate warming over the next 50 years will facilitate the establishment of circumpolar pink salmon populations in Arctic rivers. Whether a warmer climate will benefit pink salmon in all Norwegian rivers remains unclear, as it is considered a cold-water species. However, pink salmon seem to be able to adapt to new conditions over a few generations. Conclusions It has already been demonstrated that pink salmon can occur in large numbers and high densities in Norwegian rivers. The impact of pink salmon on biodiversity and ecosystems in Norwegian waters depends on their numbers. This is valid for all aspects of the river systems. A low number of pink salmon are likely of little consequence, whereas abundant spawning pink salmon in a river may have substantial impact on native salmonids, as well as on water quality and biodiversity. Thousands of spawners will possibly produce millions of offspring that may impact small invertebrates and crustaceans negatively and compete with native salmonids for food and space after hatching. The impact in the sea also depends on the abundance of pink salmon, as they may compete with native salmonids and other species for food as well as have other impacts on the food-web of marine ecosystem. The likelihood of spreading of disease to native wild fish, as well as to aquaculture fish, is also directly correlated with the number of pink salmon. However, only a few fish may have a serious impact if heavily infested with a pathogen to which native wild fish or aquaculture fish are susceptible, and conditions favour transmission. The current increasing trend in sea-surface temperatures and reduced ice cover seem to benefit the survival of pink salmon in the sea, and the projected climate change may enhance this. The impact of a warmer climate on the river stages of pink salmon is less clear. The effects of further climate change may introduce unexpected interactions with pathogens and with other species, as the accelerating change since about 2010 has been moving the Arctic Ocean into previously unobserved temperature regimes. Feasible measures to reduce the impact of pink salmon in rivers include targeted fishing adapted to local conditions. Experience from 2017 and 2019 shows that such efforts are effective and can decrease or even eliminate the threat of pink salmon to native salmonids and biodiversity in individual rivers, at least in smaller rivers. In order to reduce the number of pink salmon and the recurring returns of pink salmon spawners to Norwegian coastal waters and rivers in general, however, concerted action on a regional, national and international level is required.

The European eel (Anguilla anguilla) is critically endangered throughout its range. Knowledge about age distribution of future spawners (silver eels) is essential to monitor the status and contribute to the recovery of this species. Determination of age in anguillid eels is challenging, especially in eels from the northern part of the distribution area where growth is slow and age at maturation can be up to 30 years or more. Eels from the river Imsa in Norway have been monitored since 1975, and this reference time series has been used to assess the stock at the European level. Population dynamics in this catchment were analyzed during the late 1980s by estimating ages on whole cleared otoliths. However, techniques for revealing annual increments on otoliths have evolved over the years sometimes yielding significant differences in age estimates. In this study, the historical otolith data were reanalyzed using a grinding and polishing method rather than reading the whole otolith. The new age estimates were considerably higher than the previous ones, sometimes by up to 29 years. Since the 1980s, mean age of silver eels only slightly increased (from 19 to 21 years in the 2010s). This was mainly due to the disappearance of younger silver eels (, We reanalyzed a historical European eel otolith collection using more recent aging techniques. New estimates of age at maturation were up to 30 years higher than previously thought. Since the decline of eels in the late 1980s, mean age of silver eels has only slightly increased, from 19 to 21 years in the 2010s. Growth (30 mm/year) has not changed since the 1980s, although eel density in the catchment has decreased.

Source at https://vkm.no/risikovurderinger/allevurderinger/handelmedpapegoyerrisikoforbestanden.4.4f159c451707644d6d8ca07f.html Parrots are one of the most species-rich groups of birds of which the majority inhabits tropical and subtropical forests. Nearly one-third of parrots are threatened with extinction (IUCN categories CR, EN or VU) and more than half of the world’s parrot species are assumed to be decreasing in numbers. Parrots are popular pets on all continents, mainly due to their colourful feathers, their capacity to mimic the human voice, and their tolerance to life in captivity. More than 250 species have been traded internationally. Since the inception of CITES in 1975, trade of about 12 million live wild sourced parrots has been registered. Currently, 55 parrot species are listed on CITES Appendix I (Norwegian CITES regulation list A) that includes the most endangered among CITES-listed animals and plants. In compliance with CITES, Norway only permits import for commercial purposes of Appendix I listed parrots bred in captivity in operations included in the Secretariat's Register (Resolution Conf. 12.10 (Rev. CoP15). Presently, 9 of the Appendix I parrot species are bred in such facilities. Import of Appendix I species to Norway requires permits both from the exporter’s CITES authority and the Norwegian Environment Agency (Norwegian CITES Management Authority). Papegøyer er populære kjæledyr i alle verdensdeler. Samtidig er omtrent en tredel av papegøyeartene utryddelsestruet. Den internasjonale naturvernunionen, IUCN, regner dem som sterkt truet, truet eller sårbare. Bestanden er trolig synkende for halvparten av alle papegøyearter. I 2020 har CITES, 55 papegøyearter på sin liste I. Listen omfatter dyr og planter som trenger sterkest beskyttelse, og tilsvarer liste A i den norske CITES-forskriften. Ni av papegøyeartene i liste I er avlet frem hos oppdrettere som er godkjent av CITES. Norge tillater bare innførsel av papegøyer fra disse oppdretterne. Import krever tillatelse både fra CITES-myndigheten i eksportlandet og fra Miljødirektoratet.

The spawning migration of Atlantic salmon has been characterized by tracking salmon carrying electronic tags as they ascend rivers, but still little is known about how natural obstacles such as waterfalls influence migratory behaviour and how such behaviours are mediated by various biotic (e.g., fish size) and abiotic (e.g., discharge, water temperature, and barometric pressure) factors. The Norwegian river Numedalslågen is interrupted by natural waterfalls ranging in height from 2 to 6 m. We tagged 113 Atlantic salmon with radio transmitters in the estuary and used stationary radio telemetry stations to track fish. Ninety‐one salmon were recorded in Numedalslågen, 39 of which remained in the river for spawning. Large salmon moved farther and faster upriver but also delayed longer and had lower daily probability to pass the second waterfall. Delay below and passage probability at the final, largest waterfall was affected by water discharge, wherein passage occurred when discharge was declining. Barometric pressure also influenced daily probability of ascent, albeit in opposite directions for each waterfall. Importantly, we also found that salmon with surgically implanted radio transmitters moved farther upriver on average and delayed less time below one of the waterfalls than those with externally attached transmitters. Although there is variance in timing arising from individual decision‐making, we showed that natural waterfalls delay progress of Atlantic salmon on their spawning migration and that both biotic (i.e., size) and abiotic (i.e., barometric pressure and discharge) factors influenced the salmon's decisions to pass waterfalls that they encounter. biotelemetry, exploitation, migration, Salmonidae, straying, waterfall

To study the effects of a dispersal barrier on migration of the semi-anadromous vimba bream in the Pärnu River, Estonia, we tagged thirty fish with acoustic transmitters and released above the barrier. Tagged fish showed variation in behaviour, and 16 different spawning movement patterns were identified. Several fish moved > 25 km upstream. Batch spawning was suggested by stops in up to four different spawning areas. The Fish descended to the sea after spawning in spring; females earlier than males. After spending on average 137 days in the sea, they returned to the river during autumn and stayed in the river on average 174 days until the next spawning. The fish were most active during sunrise and sunset. In conclusion, the study shows that the dam prevents a diversification of migration behaviour and the associated expansion of spawning areas. A more efficient fishway could promote population growth and improve stock status. Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)

Småblank er den eneste rent elvelevende laksen i Europa, og finnes kun i øvre deler av Nam-senvassdraget. Størrelsen på bestanden er ukjent, men det er grunn til at tro at bestandstettheten har gått ned siden 1950- tallet, siden det i dag fanges mindre småblank tross større innsats. I tillegg vet vi at egnet habitat har forsvunnet på grunn av at tidligere strie elvepartier er gjort om til stilleflytende områder og magasiner på grunn av kraftreguleringen. Eksisterende kunnskap om habitatbruk og vandringsatferd hos småblank er sparsom. Hensikten med denne undersøkelsen er derfor å kartlegge utstrekningen av hjemmeområdet (home range) til småblank, hvilke typer habitat som benyttes, samt om småblank har vandringer mellom ulike deler av elva. I perioden fra august 2014 til august 2017 ble i alt 140 småblank og 17 ørret fanget, merket med radiosender og peilet manuelt og med automatiske lyttestasjoner. Videre ble 46 småblank merket med akustiske sendere og peilet med automatiske lyttestasjoner. Alle småblank merket med radio eller akustisk sender, samt ytterligere 89 småblank (275 i alt) ble i tillegg merket med et PIT-merke for å kunne kjenne dem igjen hvis de gjenfanges senere. Resultatene viste at småblank er langt mer stasjonær enn det som er kjent hos andre relikte laksestammer. De merkete fiskene oppholdt seg halvparten av tiden innenfor et område på 1123 m2 og 95 % av tiden innenfor et område på 4416 m2. Den maksimale avstanden mellom peilepunktene for individuelle fisk var i gjennomsnitt 242 meter, noe som i praksis innebærer at fiskene oppholdt seg innenfor samme del av elva gjennom hele undersøkelsesperioden. Det var stor individuell variasjon i størrelsen på hjemmeområdet. Generelt var hjemmeområdet større for fisk i den øvre del av undersøkelsesområdet, og arealet de brukte økte med alderen på fisken. Hjemmeområdet om høsten var større i den regulerte hovedelva enn i den uregulerte sideelva Mellingselva, og kondisjonsfaktoren var lavere hos individer i den regulerte delen av elva. Dette tyder på at forholdene for småblank er bedre i den uregulerte sideelva enn i hovedløpet der de to elvene renner sammen. Småblank oppholdt seg i områder hvor substratet hadde partikkelstørrelse 16-35 cm (stor stein) og 2-15 cm (grus og småstein). I begge typer substrat finnes det egnete skjulrom for fisken, og den observerte variasjon i substratbruk skyldes antakelig i større grad habitattilgjengelighet enn habitatpreferanser. Videre ble småblank oftest observert i områder med relativt høye (50-100 cm/s) eller moderate vannhastigheter (20-50 cm/s). Slike områder gir elvelevende fisk muligheter for å stå i strømmen og beite på drivende invertebrater (drivfauna). Småblank i Mellingselva hadde større hjemmeområde enn ørret, mens de to artene hadde lignende habitatbruk med hensyn til vannhastighet, vanndybde og bunnsubstrat. Ørret hadde jevnt over høyere kondisjonsfaktor enn småblank. Gytemoden småblank ble observert fra 15. september til 29. oktober, mens det fra 24. november kun ble observert utgytt fisk. Dette tyder på at gytetidspunktet til småblank i hovedsak er i løpet av september og oktober. Observasjoner av at småblanken er forholdsvis stasjonær, også i gyteperioden i oktober, er med på å forklare hvorfor småblanken er oppdelt i genetisk atskilte bestander med begrenset genflyt. Når småblanken samtidig foretrekker strømrike habitat, bør en, sett i et forvaltningsmessig perspektiv, ta vare på de gjenværende strømrike deler av Øvre Namsen, samt å forsøke å gjenskape ytterligere slike områder ved å fjerne terskler i aktuelle områder. Migration and habitat use of the relict Atlantic salmon småblank

Havn, T.B., Solem, Ø., Kraabøl, M., Ulvan, E.M., Holthe, E., Puffer, M., Thorstad, E.B. & Økland, F. 2018. Vandring hos sjøørret i Driva etter etablering av fiskesperre. NINA Rapport 1416. Norsk institutt for naturforskning. Laksebestanden i Driva har vært smittet med parasitten Gyrodactylus salaris siden midten av 1970-tallet. I forbindelse med planlagte utryddelsestiltak mot parasitten er det ved Snøvassfossan etablert ei fiskesperre som skal stoppe oppvandring av all fisk. Formålet med denne langtidssperra er å hindre framtidig produksjon av laks oppstrøms sperra. Etter hvert som tidligere årganger av laksunger smoltifiserer og vandrer ut, vil vassdragsavsnittene oppstrøms sperra bli fri for både for verter og parasitter. Etter at smitteforekomst i øvre og midtre deler av vassdraget er fjernet gjennom sanering, vil det gjennomføres kjemisk behandling i de nedre delene av vassdraget. Fiskesperra vil bli fjernet så snart Driva og øvrige deler av smitteregionen er friskmeldt. Siden sjøørret ikke er langtidsvert for Gyrodactylus salaris vil det i tiltaksperioden gjennomføres en rekke bevaringstiltak for å sikre en livskraftig bestand av sjøørret i Driva. Ett av tiltakene er å flytte sjøørret over fiskesperra slik at den kan ta i bruk områdene ovenfor. Vassdragsavsnittene oppstrøms sperra utgjør omtrent 70 % av anadrom strekning, og det er derfor viktig at sjøørret som flyttes opp tåler håndteringen og vandrer opp til de tilgjengelige gyteområdene. Siden sjø-ørretbestanden i Driva har en høy andel flergangsgytere, er det også viktig at utvandrende sjø-ørret overlever passering av sperrestedet etter endt gyting. Formålet med prosjektet var derfor å (1) undersøke atferd og overlevelse hos nedvandrende støing over sperra, og (2) kartlegge oppvandring, overlevelse og fordeling i vassdraget oppstrøms fiskesperra hos oppflyttet sjøørret. I mai 2017 ble 29 støinger av sjøørret og seks støinger av laks fanget på sportsfiskeutstyr ovenfor sperra, radiomerket og gjenutsatt. I september 2017 ble 44 oppvandrende sjøørret fanget i fisketrappa ved sperra, radiomerket og satt ut enten rett oppstrøms sperra (18 individer) eller ved Romfo bru (26 individer). Fiskens atferd, fordeling, passering av sperra og utvandring ble registrert av fem automatiske loggestasjoner plassert ved sperra og andre strategiske steder i vassdraget. I tillegg ble fiskens posisjon i elva registrert ved noen manuelle peilinger ved bruk av bil, inkludert i gytetida. Alle støingene som passerte fiskesperra under utvandring om våren overlevde på kort sikt. Langtidsoverlevelsen var også høy, siden 76 % av sjøørreten returnerte til elva etter sjøopphold på 57-116 dager. Noen av de oppvandrende fiskene passerte sperra etter gyting om høsten, men på grunn av en begrenset studieperiode og batteriliv på radiosenderne er det vanskelig å gi et presist estimat på overlevelse hos disse. Selv om overlevelsen hos radiomerket fisk under nedvandring var høy, viser funn av annen død fisk på sperrerista at det forekommer en viss dødelighet. Trolig vil jevnlig rensing av rista for trær, kvist og annet materiale redusere denne dødeligheten. All sjøørret som ble flyttet opp overlevde håndtering og merking, men de hadde forholdsvis korte vandringsavstander videre oppover i vassdraget. Mesteparten fordelte seg på kjente gyteplasser opp til Grensehølen nedstrøms Gråura. Lengste vandringsavstand oppstrøms fra utsettingsstedet var 26 kilometer og ble registrert for seks fisker som oppholdt seg ved Detlia i gytetida. Enkelte av fiskene vandret betydelig kortere, og åtte fisker ble værende i området like oppstrøms fiskesperra. I tillegg vandret to fisk nedstrøms over fiskesperra før gytetiden, og eventuell gyting var derfor trolig nedenfor sperra. Årsaker til at fiskene vandret kort kan være at de ble flyttet over sperra sent i sesongen, og at vannføringen og temperaturen var lav og varierte lite frem til gyting. I tillegg kan håndteringen i forbindelse med oppflytning og radiomerking føre til kortere vandringsavstand. Imidlertid var det en tendens til at fisk som ble satt ut på Romfo vandret lengre fra utsettingsstedet enn de som ble satt ut rett ovenfor sperra. Flytting av fisk et stykke oppstrøms sperra kan dermed bidra til en bedre fordeling av gytefisk over et større område.

This is the peer reviewed version of the following article: Eldøy, S.H., Davidsen, J.G., Thorstad, E.B., Whoriskey, F.G., Aarestrup, K., Næsje, T.F., ... Arnekleiv, J.V. (2017). Marine depth use of sea trout Salmo trutta in fjord areas of Central Norway. Journal of Fish Biology, 91, 1268-1283. https://doi.org/10.1111/jfb.13463, which has been published in final form at https://doi.org/10.1111/jfb.13463. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. The vertical behaviour of 44 veteran sea trout Salmo trutta (275–580 mm) in different marine fjord habitats (estuary, pelagic, near shore with and without steep cliffs) was documented during May–February by acoustic telemetry. The swimming depth of S. trutta was influenced by habitat, time of day (day v. night), season, seawater temperature and the body length at the time of tagging. Mean swimming depth during May–September was 1·7 m (individual means ranged from 0·4 to 6·4 m). Hence, S. trutta were generally surface oriented, but performed dives down to 24 m. Mean swimming depth in May–September was deeper in the near‐shore habitats with or without steep cliffs (2·0 m and 2·5 m, respectively) than in the pelagic areas (1·2 m). May–September mean swimming depth in all habitats was slightly deeper during day (1·9 m) than at night (1·2 m), confirming that S. trutta conducted small‐scale diel vertical movements. During summer, S. trutta residing in near‐shore habitat progressively moved deeper over the period May (mean 1·1 m) to August (mean 4·0 m) and then reoccupied shallower areas (mean 2·3 m) during September. In winter (November and February), individuals residing in the innermost part of the fjords were found at similar average depths as they occupied during the summer (mean 1·3 m). The swimming depths of S. trutta coincide with the previously known surface orientation of salmon lice Lepeophtheirus salmonis. Combined with previous studies on horizontal use of S. trutta, this study illustrates how S. trutta utilize marine water bodies commonly influenced by anthropogenic factors such as aquaculture, harbours and marine constructions, marine renewable energy production or other human activity. This suggests that the marine behaviour of S. trutta and its susceptibility to coastal anthropogenic factors should be considered in marine planning processes.

European grayling (Thymallus thymallus) is a popular recreational fish that may be lifted out of the water to facilitate hook removal or for admiration. To evaluate the effects of air exposure and angling-induced exhaustive exercise on released grayling condition, we assessed blood physiology and reflexes of grayling after angling and air exposure in the subarctic River Lakselva (Norway) at midsummer temperatures (i.e., 17–18 °C). Blood samples were drawn 30 min after angling and analyzed for lactate anions, glucose, sodium ions, and pH. Reflex impairment was determined with orientation and tail grab reflex action assessments immediately after landing, after air exposure, and after 30 min holding. Blood physiology did not indicate an exacerbating effect of air exposure relative to just angling-induced exercise, but significant and prolonged reflex impairment was associated with the 120 s air exposure interval. Anglers must take care to minimize air exposure to adhere to best handling practices.

External tagging of fish with electronic tags has been used for decades for a wide range of marine and freshwater species. In the early years of fish telemetry research, it was the most commonly used attachment method, but later internal implants became preferred. Recently, the number of telemetry studies using external tagging has increased, especially with the development of archival tags (data storage tags, DSTs), pop-up satellite archival tags (PSATs) and other environment-sensing tags. Scientific evaluations of the tagging method are rather scarce for most species. We identified 89 publications, reporting effects of external tagging for 80 different fish species, which constitute the main basis for this review. External attachment holds certain benefits compared to other tagging methods, for example, speed of application, and it may be the only option for fishes with a body shape unsuitable for surgical implantation, or when using tags with sensors recording the external environment. The most commonly reported problems with external tags are tissue damage, premature tag loss, and decreased swimming capacity, but the effects are highly context dependent and species specific. Reduced growth and survival have also been recorded, but direct mortality caused by external tagging seems rare. Most of the studies reviewed evaluate tag retention, survival, and tissue reactions. There is a general need for more research on the effects of external tagging of fish with electronic tags, but particularly there are few studies on predation risk, social interactions, and studies distinguishing capture and handling effects from tagging effects. For PSATs, especially those that are large relative to fish size, there are particular problems with a high proportion of premature tag losses, reduced swimming capacity, and likely increased predation, but there remains a paucity of tag effect studies related to the use of PSATs. Before embarking on a field study employing external tagging with electronic tags, we recommend the use of appropriate pilot studies, controlled where possible, to quantify potential impacts of tagging. Telemetry, Tag attachment, Archival tag, PSAT, Survival, Tissue damage, Tag retention, Growth, Swimming, Drag, Entanglement, Biofouling, Predation

Salmon lice are external parasites on salmonids in the marine environment. During recent years, sea lice abundance has been increased due to the presence of salmon farming using on-growing floating seas-cages. Amongst salmonids, sea trout is especially vulnerable to salmon lice infestations, because during their marine residence they typically remain in coastal waters, where open net cage Atlantic salmon farms typically are situated. In this report the existing knowledge about the effects of salmon lice on sea trout populations in the NE Atlantic coastal waters has been reviewed, assessing the current situation of this problematic. Salmon aquaculture increase the salmon lice abundance, which affect negatively on sea trout populations as an increase in marine mortality, changes in migratory behaviour and reduction of marine growth. These conclusions are based on published studies that range from those investigating the effects of salmon lice on individual fish, both in the laboratory and the field, to analyses of their impacts on populations in the wild. In sum, the combined knowledge from the reviewed studies provides evidence of a general and pervasive negative effect of salmon lice on sea trout populations, especially in intensively farmed areas. The effects induced by elevated salmon lice levels inevitably imply a reduction in numbers and body size of sea trout returning to freshwater for spawning, affecting the local population dynamic and recreational and commercial fisheries in the most impacted areas.

In this study, behaviour and survival following catch-and-release (C&R) angling was investigated in wild Atlantic salmon Salmo salar (n = 75) angled on sport fishing gear in the River Otra in southern Norway at water temperatures of 16⋅3–21⋅1∘ C. Salmo salar were tagged externally with radio transmitters and immediately released back into the river to simulate a realistic C&R situation. The majority of S. salar (91%) survived C&R. Most S. salar that were present in the River Otra during the spawning period 3–4 months later were located at known spawning grounds. Downstream movements (median furthest position: 0⋅5 km, range: 0⋅1–11⋅0 km) during the first 4 days after release were recorded for 72% of S. salar, presumably stress-induced fallback associated with C&R. Individuals that fell back spent a median of 15 days before commencing their first upstream movement after release, and 34 days before they returned to or were located above their release site. Mortality appeared to be somewhat elevated at the higher end of the temperature range (14% at 18–21∘ C), although sample sizes were low. In conclusion, C&R at water temperatures up to 18∘ C had small behavioural consequences and was associated with low mortality (7%). Nevertheless, low levels of mortality occur due to C&R angling and these losses should be accounted for by management authorities in rivers where C&R is practised. Refinement of best practices for C&R may help to reduce mortality, particularly at warmer temperatures. biotelemetry; fisheries management; radio-telemetry; recreational fishing.

Som en oppfølging av tidligere garnundersøkelser i nedre deler av 12 sideelver til Øvre Namsen, ble det i 2011 og 2012 gjennomført undersøkelser med drivtellinger i Frøyningselva, Flåttådalselva, Grøndalselva og Lindsetelva. I tillegg ble det gjennomført drivtellinger i Tromselva, Stillelva og Vesterelva. Denne rapporten sammenfatter resultatene fra alle disse undersøkelsene, samt noen av resultatene fra undervannsobservasjoner som ble gjennomført i Mellingselva i 2008. Tidligere undersøkelser i form av elektrisk fiske eller garnfiske har påvist småblank i seks av de åtte undersøkte elvene. I Stillelva og Vesterelva er det tidligere ikke påvist småblank, selv om ikke er noen fysisk barriere for oppvandring fra Mellingselva via Mellingsvatnet. Drivtellinger i juli 2012 påviste med rimelig grad av sikkerhet at det er småblank i begge disse tilløpselvene. Imidlertid tilsier svært få observasjoner at det neppe er noen tett bestand av småblank i noen av disse elvene. Dette skyldes trolig at nedre deler av begge elvene er svært stilleflytende med fint bunnsubstrat, slik at tilgangen på egnet habitat for småblank er sterkt begrenset i både Stillelva og Vesterelva. I tillegg er det trolig sterk konkurranse fra aure i elvene, siden de benyttes som gyte- og oppvekstområde for den tallrike aurebestanden i Mellingsvatnet. Mellingselva framstår som det viktigste leveområdet for småblank ved siden av hovedelva, og småblank finnes på hele elvestrekningen fra utløpet av Mellingsvatnet til samløpet med Namsen. I juli 2008 ble det observert 71 småblank og 53 aure fordelt på 17 transekter i øvre del av Mellingselva. De største forekomstene av småblank ble registrert i et rasktflytende parti som ligger 500-700 meter oppstrøms innløpet av sideelva Smalvasselva, der småblank utgjorde 75 % av all observert fisk. Ut fra undervannsstudiene som også kartla habitatbruk og habitatpreferanse hos begge arter, synes småblank å foretrekke de mest rasktflytende områdene av elvetverrsnittet, og ble observert i størst tetthet på strie fallstrekninger med nakent berg og store steiner. Aure ble i større grad observert i stilleflytende elvepartier og langs land i rasktflytende elvepartier, der aure utgjorde 73 % av all observert fisk. Frøyningselva har mange likhetstrekk med Mellingselva. Det er en forholdsvis lang sideelv som ligger nedstrøms en større innsjø med tilløpselver som er potensielt tilgjengelig for småblank. Frøyningselva har en veksling mellom grunne, rasktflytende strykområder og dype, sentflytende kulpområder. Tidligere undersøkelser med garnfiske har vist en brukbar forekomst av småblank i nedre deler av Frøyningselva. Under drivtellingene i august 2011 ble det observert til sammen 10 småblank og 32 aurer på en 3-4 km lang elvestrekning nedstrøms Frøyningen. Observasjon av småblank like nedstrøms Frøyningen tyder på at Frøyningen og tilløpselvene er potensielle leveområder for småblank. Flåttådalselva er i likhet med Mellingselva og Frøyningselva et sidevassdrag med stort potensial for småblankproduksjon. Ut over en lang elvestrekning som trolig er tilgjengelig for småblank, er det god forekomst av habitattyper som ifølge habitatbruksstudiene i Mellingselva er preferert av småblank. Undervannsobservasjonene i midtre deler i 2011 (11 småblank og 111 aure) og øvre deler i 2012 (ingen småblank og 22 aure) tyder imidlertid på en svært tynn bestand i øvre deler av Flåttådalselva, selv om habitatforholdene synes velegnet for småblank (god tilgang på rasktflytende områder med grovt bunnsubstrat). Det er ikke mulig å fastslå om lav tetthet er en naturlig situasjon som følge av vanskelige oppvandringsforhold, eller om den lave forekomsten i øvre deler skyldes menneskelige inngrep. Lindsetelva er et annet sidevassdrag med stort potensial for småblankproduksjon. Sidevassdraget består av en rekke større og mindre elver, vann og tjern. I nedre del av hovedelva er det god forekomst av habitattyper som er vurdert godt egnet for småblankproduksjon. Hovedelva har en relativt høy vannføring som følge av et stort nedbørsfelt, og vannføringen er stabilisert på grunn av vannmengdene i de tallrike vann og tjern. Et parti med mange mindre fossefall hindrer trolig fri oppvandring av småblank fra nedre til midtre og øvre deler. Under drivtelling på en tre kilometer lang strekning oppstrøms antatt vandringsstopp i 2012 ble det observert 286 aure og ingen småblank. Det kreves imidlertid mer omfattende undersøkelser for å få et sikrere bilde av forekomst i Lindsetelva. Grøndalselva har vært påvirket av tungmetallutslipp fra gruvedrift i Skorovass. I og med at både småblank og aure er sensitive for tungmetaller, er det overveiende sannsynlig at gruvedriften har påvirket fiskesamfunnet negativt. Under drivtellinger i 2012 ble det observert to småblank og 197 aure. Basert på gjennomførte undersøkelser i senere år synes det ikke å være en tallrik bestand med småblank i Grøndalselva. Denne konklusjonen er i tråd med lokalbefolkningens oppfatning om at det ikke har vært en fast bestand av småblank i elva. Det er ikke mulig å fastslå om den nåværende situasjonen for småblank og aure er en langtidseffekt av forurensning, eller om dagens fiskesamfunn gjenspeiler naturlige forhold. Tromselva har et forholdsvis høyt fossefall like oppstrøms utløpet til Namsen, som sannsynligvis er et absolutt hinder for oppvandring av småblank. Det er tidligere påvist småblank på den korte elvestrekningen nedstrøms fossefallet. Oppstrøms fossefallet er det ikke påvist småblank, verken i tidligere undersøkelser eller ved drivtellingene i 2012. Det er derfor vurdert som sannsynlig at det ikke er noen livskraftig bestand av småblank i Tromselva, men det kan ikke utelukkes at det er en svært tynn bestand som ikke er påvist i undersøkelsene. Undervannsobservasjoner har i likhet med andre feltmetoder begrensninger og usikkerheter som påvirker påliteligheten. Oppdagelsessannsynligheten påvirkes av fysiske forhold som sikt under vann, vannhastighet, vanndybde og elvebunnens beskaffenhet. I tillegg øker sannsynligheten for å overse fisk med avtakende fiskestørrelse og grad av kamuflasje. Det er verdt å merke seg at resultatene fra drivtellingene har en kvalitativ natur og er mest egnet for å kartlegge utbredelse av småblank. Kartleggingen har også en ensidig natur; påvisning viser at det er småblank i undersøkt område, mens manglende påvisning bare er en indikasjon på at det ikke er småblank i området. Dersom formålet er å kartlegge mengde småblank bør semikvantitative metoder anvendes, eksempelvis i form av registrering av småblank langs en rekke transekter som er representative for det undersøkte området. I og med at nyere undersøkelser med garnfiske og undervannsobservasjoner i sidevassdrag viser en videre utbredelse av småblank enn tidligere antatt, er det god grunn til å anta at små- blank kan ha videre utbredelse også i andre, dårligere undersøkte sidevassdrag til Namsen. For å få en bedre oversikt over absolutt utbredelse av småblank i Namsenvassdraget er det behov for ytterligere kartlegging i sidevassdrag. Ut fra størrelse og potensiell betydning anbefaler vi mer omfattende undersøkelser i Mellingselva, Smalvasselva, Flåttådalselva, Lindsetelva og Nesåa. © Norsk institutt for naturforskning. Publikasjonen kan siteres fritt med kildeangivelse.

Undersøkelsene i Namsfjorden og Namsenvassdraget er en videreføring av undersøkelser som ble påbegynt i 2012, og videreføres i 2014. Denne rapporten er derfor en framdrifts-rapport fra undersøkelsene. Hovedmålsettingen med undersøkelsene er å skaffe kunn-skap slik at man kan gjøre sikrere beregninger av den reelle andelen rømt oppdrettslaks i lakseelver. De ulike delmålene har vært å:  Vurdere sikkerheten i dagens metoder for beregning av andel oppdrettslaks i gyte-bestander av villaks.  Sammenligne bitevillighet og fangsteffektivitet for oppdrettslaks og villaks i elva.  Sammenligne vandringsmønsteret til oppdrettslaks og villaks i elva.  Sammenligne fordeling og atferd til oppdrettslaks og villaks i gytetida.  Sammenligne antall oppdrettslaks som fanges i fjordsystemet med antall som vandrer opp i nærliggende elver.  Undersøke tidspunktet for innvandring til fjorden av villaks og oppdrettslaks.  Bedre grunnlaget for målrettet oppfisking av oppdrettslaks i elva. Innvandring av villaks og rømt oppdrettslaks til Namsfjorden ble undersøkt med fangst av laks i to doble kilenøter fra 16.05. til 10.09.2013. Maskevidden som ble benyttet (58 mm) medfører fangst av få laks mindre enn ca. 57 cm totallengde, og små laks var derfor un-derrepresentert i fangstene. I kilenøtene ble det totalt fanget 1046 villaks, 65 rømt oppdrettslaks, 6 kultiverte laks og 15 laks med usikkert opphav. Rømt oppdrettslaks vandret senere inn Namsfjorden enn villak-sen. Villaks ble hovedsakelig fanget mellom 27.05. og 11.08., mens rømt oppdrettslaks ble hovedsakelig fanget mellom 29.07. og 18.07. Blant villaksen var 14 % smålaks (< 66 cm), 64 % mellomlaks (66-88 cm) og 22 % storlaks (> 88 cm). Blant oppdrettslaksen var 11 % smålaks, 78 % mellomlaks og 11 % storlaks. Lengden til ensjøvinter villaks varierte mellom 52 og 73 cm (gjennomsnitt 62 cm), mens lengden til tosjøvinterlaks varierte mellom 57 og 101 cm (gjennomsnitt 76 cm), og lengde-fordelingen til tresjøvinterlaks varierte fra 66 til 114 cm (gjennomsnitt 88 cm). Det var til dels stort overlapp i lengden til sjøvinterårsklassene, hvor 43 % av tosjøvinterlaksen hadde lengder som lå innenfor lengdefordelingen til ensjøvinterlaks, mens 92 % av tresjøvinter-laksen hadde lengder som lå innenfor lengdefordelingen til tosjøvinterlaks. Namsen, Namsenvassdraget, Namsfjorden, Nord-Trøndelag, villaks, rømt oppdrettslaks, kilenotfangst, atferd, radiotelemetri, fangst per innsats, stangfiske, gytetid © Norsk institutt for naturforskning. Publikasjonen kan siteres fritt med kildeangivelse.

Thorstad, E.B., Todd, C.D., Bjørn, P.A., Gargan, P.G., Vollset, K.W., Halttunen, E., Kålås, S., Uglem, I., Berg, M. & Finstad, B. 2014. Effects of salmon lice on sea trout. A litterature review. NINA Rapport 1044. 162 s. Salmon lice are external parasites on salmonids in the marine environment. Farmed salmonids also act as hosts for salmon lice; therefore open net cage farms can increase the production of infective larvae in coastal areas. The aim of this report is to review the existing knowledge on the effects of salmon lice on wild sea trout and focuses on reports in the peer-reviewed primary scientific literature. Fro this reason, references to so-called "grey literature" reports has been minimized. The studies reviewed here range from laboratory and field investigations of the effects of salmon lice on individual fish, to analyses of impacts on wild populations. © Norsk institutt for naturforskning. Publikasjonen kan siteres fritt med kildeangivelse.