Recent improvement of fish populations in the Jarfjord Mountains in northern Norway due to reduced surface water acidification

Appendix 10/15 of the publication "State of the environment in the Norwegian, Finnish and Russian border area 2007" (The Finnish Environment 6/2007)

On the numerous concepts in invasion biology

Source at https://doi.org/10.1007/s10530-005-0710-6.The study of biological invasions has triggered the production of a diversity of concepts. The terminology has, however, often been applied inconsistently and inaccurately. This article lists and assesses the most commonly used terms and concepts in invasion ecology. In each case the most coherent definition and use is suggested

Annual and diel activity cycles of a northern population of the large migratory cyprinid fish asp (Leuciscus aspius)

Little is known about the exact movement parameters of migratory cyprinids listed as conservation priorities. A northern population of predatory asp, listed on the Bern Convention Appendix III, was studied in a near natural lake–river ecosystem by tracking adult fsh tagged with acoustic transmitters for 32 months. Activity levels in terms of swimming speed, swimming distance and movement range were four times higher during the warmer part of the year (water temperatures>12–15 °C, April/May–September), which coincides with their main feeding period, than other times of the year. All fsh had an annual riverine movement range larger than 40 km (max 110 km). Asp activity was afected by light, habitat type and water discharge. For most of the year, activity levels, in terms of number of movements per time unit, were higher during dawn and dusk than during day and night. Under poor light conditions and low temperatures, activity was also relatively high during the day. Fish were more likely to swim upstream around sunrise or during the day than during other diel periods. Knowledge about highactivity periods, which may render the fsh vulnerable to fshing and other impacts, can be used to develop and evaluate fshing regulations. Large annual movement ranges highlight the need for extensive continuous river systems open for migration between essential habitats. This study emphasises the need for region-specifc research on the ecology and behaviour of fsh populations in order to facilitate protection of the populations in the face of negative human impacts.publishedVersio

Growth of invasive pink salmon (Oncorhynchus gorbuscha) at sea assessed by scale analysis

Invasive pink salmon (Oncorhynchus gorbuscha) has been present in variable, but low, numbers in Norwegian waters since c. 1960, but beginning in 2017 their numbers have exploded in rivers in northern Norway, with considerable numbers also recorded in rivers in southern Norway and other countries bordering the North Atlantic. Analysis of pink salmon scales from two rivers draining to the western Barents Sea showed declining growth during the first weeks after entering the sea, and some individuals even showed a pronounced growth arrest, based on detailed scale circulus analyses. This was followed by a period of growth increase and stability during late summer and autumn, which may reflect a transition to better food sources, as the fish migrate from coastal waters to the open ocean, and as they grow larger and can eat larger and more energy efficient food items. Growth declined to a minimum during winter. Fish body size at spawning was positively correlated with the distance from scale focus to the last winter circulus, as well as with the number of circuli. When dividing scale growth into three periods, better growth during the first period at sea was related to increased fish body length at spawning, but this early growth explained only a minor part (6%) of the variation in final body length. The reason for this may be large individual variation in growth combined with large mortality during the first weeks at sea. If mortality is selective, removing fish with poor growth may reduce a correlation between early growth and body size at spawning. Scale growth during late summer and early autumn explained more of the variation in fish length at spawning (27%). Hence, late summer and early autumn was likely an important period for marine growth and survival in the invasive pink salmon

Invader population speeds up life history during colonization

We explore the long-term developments in population biology and life history during the invasion and establishment of the fish species vendace Coregonus albula in a subarctic watercourse by comparing life-history traits and molecular genetic estimates between the source and the colonist population. The two populations exhibited highly contrasting life-history strategies. Relative to the source population, the colonist population was characterized by slower somatic growth rates, earlier sexual maturation at smaller individual size, higher mortality rates and a shorter life span. The two populations could also be significantly discriminated by the genetic markers. Limited founder effects were detected from heterozygote deficit and reduced allelic richness in the colonist population, but both populations were associated with relatively high genetic diversity. The study reveals that the invasion into a new environment induced large changes in life-history strategy, with typical r-selected traits being more prominent in the colonist than in the source population. We discuss the mechanisms that may explain the observed life-history differences between the source and the colonist population, and argue that the accelerated life history of the colonist population represents an adaptive pioneer strategy aimed at fast population increase during colonization and establishment

Intercalibration of the national classifications of ecological status for Northern Lakes: Biological Quality Element: Fish fauna

The European Water Framework Directive (WFD) requires the national classifications of good ecological status to be harmonised through an intercalibration exercise. In this exercise, significant differences in status classification among Member States are harmonized by comparing and, if necessary, adjusting the good status boundaries of the national assessment methods. Intercalibration is performed for rivers, lakes, coastal and transitional waters, focusing on selected types of water bodies (intercalibration types), anthropogenic pressures and Biological Quality Elements. Intercalibration exercises were carried out in Geographical Intercalibration Groups - larger geographical units including Member States with similar water body types - and followed the procedure described in the WFD Common Implementation Strategy Guidance document on the intercalibration process (European Commission, 2011). The Technical reports are organized in volumes according to the water category (rivers, lakes, coastal and transitional waters), Biological Quality Element and Geographical Intercalibration group. This volume addresses the intercalibration of the Northern Lake GIG Fish fauna ecological assessment methods. Two countries (Norway and Sweden) participated in the intercalibration exercise and harmonised their lake fish fauna systems. The results were approved by the WG ECOSTAT and included in the EC Decision on intercalibration (European Commission, 2018).JRC.D.2-Water and Marine Resource

Developing ecosystem service indicators: experiences and lessons learned from sub-global assessments and other initiatives

People depend upon ecosystems to supply a range of services necessary for their survival and well-being. Ecosystem service indicators are critical for knowing whether or not these essential services are being maintained and used in a sustainable manner, thus enabling policy makers to identify the policies and other interventions needed to better manage them. As a result, ecosystem service indicators are of increasing interest and importance to governmental and inter-governmental processes, including amongst others the Convention on Biological Diversity (CBD) and the Aichi Targets contained within its strategic plan for 2011-2020, as well as the emerging Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES). Despite this growing demand, assessing ecosystem service status and trends and developing robust indicators is o!en hindered by a lack of information and data, resulting in few available indicators. In response, the United Nations Environment Programme World Conservation Monitoring Centre (UNEP-WCMC), together with a wide range of international partners and supported by the Swedish International Biodiversity Programme (SwedBio)*, undertook a project to take stock of the key lessons that have been learnt in developing and using ecosystem service indicators in a range of assessment contexts. The project examined the methodologies, metrics and data sources employed in delivering ecosystem service indicators, so as to inform future indicator development. This report presents the principal results of this project

The dynamics of habitat use in the saimonid genera Coregonus and Salvelinus: ontogenetic niche shifts and polymorphism

SYNOPSIS OF RESULTS Ontogenetic niche shifts Papers I, II, III, IV, VIII, and IX show that both vendace, whitefish and Arctic charr perform ontogenetic niche shifts. All species start their lives in the benthic zone and turn to utilizing the pelagic zone at a later age. In vendace, the whole cohort performs a niche shift to the pelagic zone during the first summer (Paper II), and continue living in this zone feeding mainly on zooplankton for the rest of the life span (Paper IV and VII). Even in the littoral zone, however, the diet of age-0 vendace is dominated by crustacean zooplankton (Paper II). Thus, the niche of vendace is narrow, and the specialist nature of the species is reflected in its pelagic zooplanktivore life in a variety of localities (Paper IV, V, VII). The observed fluctuating or regularly oscillating year class strengths in vendace populations (Paper VI) are probably due to the narrow niche of the species, restricted both in the diet and habitat dimension, creating strong intra-specific interactions. The generalist nature of Arctic charr and whitefish is indicated by their variable diet and habitat use within and between lakes. The two species resemble each other in their patterns of ontogenetic niche shifts. Populations of both species maintain a basis in the epibenthic habitat, where all size groups of the population usually are present (Paper III, VIII, IX). Among certain size groups, some fish perform a seasonal habitat shift to the pelagic zone when zooplankton abundance is high. In Mjøsa whitefish, the habitat shift occurs just prior to sexual maturity at a size of 25 cm (Paper III and IV). In Femund whitefish, the habitat shift occurs at a size of between 20 - 25 cm (Paper VIII), and is mainly performed by the most slow-growing morph, which matures sexually from a body length of 25 cm onwards. In both lakes the habitat shift involves few fish larger than 35 cm, and only a part of the 25 - 35 cm length group. The change in habitat may therefore be termed niche expansion rather than niche shift. In Mjøsa, the niche of whitefish larger than 35 cm is restricted to feeding in the deep benthic zone on one particular prey item (Pallasea quadrispinosa). In Femund, large whitefish utilize the shallow benthic zone (Paper VIII, Sandlund and Næsje 1986). The ontogenetic development of the niches differs among the Arctic charr morphs in Thingvallavatn (Paper IX). All morphs start their lives in the littoral zone, feeding mainly on chironomid larvae. The benthic morphs remain in the littoral zone, but their diet includes an increasing proportion of the snail Lymnaea peregra. Thus, there is a rather moderate niche change in the benthic morphs (SB- and LB-charr). The pelagic morphs, on the other hand, expand their habitat to include both the profundal and the pelagic zone, and their diet includes both zoobenthos and zooplankton, from an age of a few months onwards. The large pelagic morph (LP-charr) performs one additional diet shift, into a diet dominated by fish (Gasterosteus aculeatus). In this system, the pelagic morphs (PL- and Pl-charr) exhibit generalists’ niches, whereas the benthic morphs (SBand LB-charr) are more specialized. The dominance of pelagic prey in the diet of pelagic whitefish (Paper II and III) and Arctic charr (Paper IX), indicates that the individual fish stay for a prolonged period in the pelagic zone. This observed pattern of niche shifts generates the hypothesis that the individuals performing the niche shift are morphologically and behaviourally better adapted to a pelagic life than the individuals remaining in the benthic habitat. Polymorphism Superficially, the occurrence of polymorphism in whitefish and Arctic charr populations does not seem to increase total population niche width. For instance, the Mjøsa whitefish (Papers I - V) utilize all main habitats (littoral, profundal, pelagic) and all prey types and sizes commonly taken by whitefish, during its lifetime. The Femund whitefish, which according to gillraker number consists of three morphs (Paper VIII), appears to use the same habitats. However, a closer analysis of the niche of each ontogenetic stage reveals differences between mono- and polymorphic stocks. E.g., the niche of juveniles is wider in polymorphic than in monomorphic whitefish populations. In Femund, juveniles were caught in the benthic zone at all depths down to 60 m (Paper VIII, Sandlund and Næsje 1986), indicating a wider habitat than among juveniles of the monomorphic Mjøsa stock, which are restricted to the littoral zone (Paper II, III). In the Thingvallavatn charr, the variation in habitat use and diet among the morphs, already from age-0, leads to a very wide total niche for this population (Paper IX). Within virtually all size and age groups of fish there are both pelagic and benthic fish. The diet of all size groups between approximately 7 - 22 cm varies from crustacean zooplankton through insects to snails. The diet of fish larger than 22 cm also includes fish. The observations on head morphology and gillraker number of the pelagic versus the benthic morphotypes in Thingvallavatn (Paper IX) support the notion that sympatric morphs are morphologically specialized to feed on different prey types in different environments. Trophic specialization makes each fish more efficient in utilizing its special resource. A condition for the occurrence of trophic specialization, however, is that there are stable resource bases available. In Thingvallavatn these bases of available resources largely consists of the snail Lymnea peregra in the benthic zone, the crustacean zooplankton and the emerging and hatching chironomids in the pelagic zone, and the sticklebacks in the epibenthic zone. The nearly complete absence of competitors has allowed for a trophical diversification and specialization in the Arctic charr population. In Femund, the number of competitors is also relatively low, and the whitefish has diversified into morphs differing in trophical morphology (Paper VIII). The three morphs have been denoted according to their spawning sites: deepwater (D-), river (R-), and shallow water (S-) whitefish. In this case the morph with the lowest number of gillrakers, i. e. the D-whitefish (28 gillrakers), utilize the pelagic zone during the period of maximum zooplankton abundance. The morphs with the denser giilraker sieves (Rwhitefish, 35 gillrakers; S-whitefish, 43 gillrakers) mainly stay in the benthic habitat. This may indicate that the connection between zooplanktivory and the number of gillrakers is not as simple as has been believed (Nikolsky 1963, Lindsey 1981, but see O’Brien 1987). The zooplankton size selection by vendace and whitefish in Mjøsa shown in Paper V also indicate a more complex connection between giilraker morphology and zooplanktivory than is often believed. It may be hypothesized that some of the differences between whitefish morphs in Femund emerge because the morphs spawn in widely different environments (Paper VIII). The hatching larvae will consequently experience different physical environments and probably different types and abundances of prey. The fact that D-whitefish has a slower growth rate and a smaller asymptotic size than the two other morphs might indicate that fish of the different morphs experience different environments for a prolonged period of time. Thus, other selection pressures of more vital importance than zooplanktivore efficiency in subadult or adult life may cause the giilraker divergence among the whitefish morphs in Femund. Polymorphism and fish community structure In temperate lakes, most invertebrate prey available to fish occur in a seasonal manner (Paper III, IV, IX), so that each fish to some degree has to shift from one prey type to another. In Mjøsa, there are in all habitats some species that are trophically more specialized than whitefish (Paper I). Thus, the possible use by whitefish of each habitat is probably restricted. Generalists like whitefish are able to balance this drawback by shifting between prey types and habitats both seasonally and through life (Paper II, III, IV), and no trophic specialization will occur in terms of e.g. polymorphism. Paper I shows that the habitat of monomorphic whitefish overlap with several of the other dominant species in Mjøsa. In the littoral zone, both perch (Perea fluviatilis) and roach (Rutilus rutilus) are numerous. Ruffe (Acerina cernua) has a benthic habitat that overlaps with the benthic whitefish population, and smelt (Osmerus eperlanus) has both a benthic and pelagic habitat, which is similar to that of whitefish. Thus, an extensive coexistence with many species appears not to restrict the habitat dimension of the age-structure component of the niche of the whitefish. The niches of polymorphic stocks are, however, expanded by means of the between-phenotype component. The polymorphic stocks of whitefish (Paper VIII) and Arctic charr (Paper IX) treated in my investigations are both found in localities with low fish fauna diversity and diverse feeding and spawning habitats

River Classification for Environmental Flow Targets

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