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Whether gill area constrains fish metabolism through oxygen limitation is a debated topic. Here, the authors provide insights into this question by analysing mass-specific metabolic rates across 44 teleost fishes extracted from FishBase. They explore whether species deviations from metabolic rates predicted by body mass can be explained by species gill area. They show that the gill area explains c. 26%–28% of species-level deviations from mass-specific metabolic rates. Their findings suggest that gill area might indeed be one of the factors limiting metabolic rate in fishes.

Competition is assumed to shape niche widths, affecting species survival and coexistence. Expectedly, high interspecific competition will reduce population niche widths, whereas high intraspecific competition will do the opposite. Here we test in situ how intra- and interspecific competition affects trophic resource use and the individual and population niche widths of two lacustrine fish species, Arctic charr and brown trout, covering a 40 year study period with highly contrasting competitive impacts prior to and following a large-scale fish culling experiment. Initially, an overcrowded Arctic charr population dominated the study system, with brown trout being nearly absent. The culling experiment reduced the littoral Arctic charr density by 80%, whereupon brown trout gradually increased its density in the system. Thus, over the study period, the Arctic charr population went from high to low intraspecific competition, followed by increasing interspecific competition with brown trout. As hypothesized, the relaxed intraspecific competition following the experimental culling reduced individual diet specialization and compressed population niche width of Arctic charr. During the initial increase of the brown trout population, there was a large dietary overlap between the two species. Over the subsequent intensified interspecific competition from the population build-up of brown trout, their trophic niche overlap chiefly declined due to a dietary shift of Arctic charr towards enhanced zooplankton consumption. Contrary to theoretical expectations, the individual and population niche widths of Arctic charr increased with intensified interspecific competition. In contrast, the diet and niche width of brown trout remained stable over time, confirming its competitive superiority. The large-scale culling experiment and associated long-term research revealed pronounced temporal dynamics in trophic niche and resource use of the inferior competitor, substantiating that intra- and interspecific competition have large and contrasting impacts on individual and population niches.

The warming trend of the Arctic is punctuated by several record-breaking warm years with very low sea ice concentrations. The nature and reversibility of marine ecosystem responses to these multiple extreme climatic events (ECEs) are poorly understood. Here, we investigate the ecological signatures of three successive bottom temperature maxima concomitant with surface ECEs between 2004 and 2017 in the Barents Sea across spatial and organizational scales. We observed community-level redistributions of fish concurrent with ECEs at the scale of the whole Barents Sea. Three groups, characterized by different sets of traits describing their capacity to cope with short-term perturbations, reacted with different timing and intensity to each ECE. Arctic species co-occurred more frequently with large predators and incoming boreal taxa during ECEs, potentially affecting food web structures and functional diversity, accelerating the impacts of long-term climate change. On the species level, responses were highly diversified, with different ECEs impacting different species, and species responses (expansion, geographical shift) varying from one ECE to another, despite the environmental perturbations being similar. Past ECEs impacts, with potential legacy effects, lagged responses, thresholds, and interactions with the underlying warming pressure, could constantly set up new initial conditions that drive the unique ecological signature of each ECE. These results highlight the complexity of ecological reactions to multiple ECEs and give prominence to several sources of process uncertainty in the predictions of climate change impact and risk for ecosystem management. Long-term monitoring and studies to characterize the vertical extent of each ECE are necessary to statistically link demersal species and environmental spatial–temporal patterns. In the future, regular monitoring will be crucial to detect early signals of change and understand the determinism of ECEs, but we need to adapt our models and management to better integrate risk and stochasticity from the complex impacts of global change. Successive extreme climatic events lead to immediate, large-scale, and diverse responses from fish in the Arctic

1.The cost of reproduction on demographic rates is often assumed to operate through changing body condition. Several studies have found that reproduction depresses body mass more if the current conditions are severe, such as high population densities or adverse weather, than under benign environmental conditions. However, few studies have investigated the association between the fitness components and body mass costs of reproduction. 2.Using 25 years of individual-based capture–recapture data from Svalbard reindeer Rangifer tarandus platyrhynchus, we built a novel Bayesian state-space model that jointly estimated interannual change in mass, annual reproductive success and survival, while accounting for incomplete observations. The model allowed us to partition the differential effects of intrinsic and extrinsic factors on both non-reproductive mass change and the body mass cost of reproduction, and to quantify their consequences on demographic rates.3. Contrary to our expectation, the body mass cost of reproduction (mean = –5.8 kg) varied little between years (CV = 0.08), whereas the between-year variation in body mass changes, that were independent of the previous year's reproductive state, varied substantially (CV = 0.4) in relation to autumn temperature and the amount of rain-on-snow in winter. This body mass loss led to a cost of reproduction on the next reproduction, which was amplified by the same environmental covariates, from a 10% reduction in reproductive success in benign years, to a 50% reduction in harsh years. The reproductive mass loss also resulted in a small reduction in survival.4. Our results show how demographic costs of reproduction, driven by interannual fluctuations in individual body condition, result from the balance between body mass costs of reproduction and body mass changes that are independent of previous reproductive state. We illustrate how a strong context-dependent fitness cost of reproduction can occur, despite a relatively fixed body mass cost of reproduction. This suggests that female reindeer display a very conservative energy allocation strategy, either aborting their reproductive attempt at an early stage or weaning at a relatively constant cost. Such a strategy might be common in species living in a highly stochastic and food limited environment.

The regulatory network of R2R3 MYB transcription factors in anthocyanin biosynthesis is not fully understood in blue-coloured berries containing delphinidin compounds. We used blue berries of bilberry (Vaccinium myrtillus) to comprehensively characterise flavonoid-regulating R2R3 MYBs, which revealed a new type of co-regulation in anthocyanin biosynthesis between members of MYBA-, MYBPA1- and MYBPA2-subgroups. VmMYBA1, VmMYBPA1.1 and VmMYBPA2.2 expression was elevated at berry ripening and by abscisic acid treatment. Additionally, VmMYBA1 and VmMYBPA1.1 expression was strongly downregulated in a white berry mutant. Complementation and transient overexpression assays confirmed VmMYBA1 and VmMYBA2 to induce anthocyanin accumulation. Promoter activation assays showed that VmMYBA1, VmMYBPA1.1 and VmMYBPA2.2 had similar activity towards dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS), but differential regulation activity for UDP-glucose flavonoid 3-O-glucosyltransferase (UFGT) and flavonoid 3'5'-hydroxylase (F3'5'H) promoters. Silencing of VmMYBPA1.1 in berries led to the downregulation of key anthocyanin and delphinidin biosynthesis genes. Functional analyses of other MYBPA regulators, and a member of novel MYBPA3 subgroup, associated them with proanthocyanidin biosynthesis and F3'5'H expression. The existence of 18 flavonoid-regulating MYBs indicated gene duplication, which may have enabled functional diversification among MYBA, MYBPA1 and MYBPA2 subgroups. Our results provide new insights into the intricate regulation of the complex anthocyanin profile found in blue-coloured berries involving regulation of both cyanidin and delphinidin branches.

From video recordings of spawning events, we quantified protective and cannibalistic behavior of Arctic charr occurring immediately after spawning. The number of fish cannibalizing on stray eggs was examined regarding (a) whether more than one male shed milt during the spawning event, that is, whether sperm competition occurred, (b) whether the sperm competition included few or many males, that is, the intensity of sperm competition, and (c) the density of fish at the spawning site. Response behavior toward egg cannibalism was also examined among females and dominant males in order to determine any parental investment toward protecting the eggs after spawning. Cannibalistic behavior was seen in almost 50% of the spawnings, and the multiple spawning events showed the highest numbers of fish cannibalizing on eggs. Both the number of males releasing milt and the number of fish approaching the spawning site were positively correlated with egg cannibalism. Sperm competition was, however, not a prerequisite for egg cannibalism. Although we also observed partial filial cannibalism, protective behavior of eggs was seen both among dominant males and females, suggesting that charr actually conduct parental care., From video recordings of spawning events, we quantified the protective and cannibalistic behavior of Arctic charr occurring immediately after spawning. Cannibalistic behavior was seen in almost 50% of the spawnings. Although partial filial cannibalism was observed, protective behavior of eggs was seen both among dominant males and females, suggesting that charr actually conduct paternal care.

The impact of remotely piloted aircraft systems (RPAS) on marine mammals remains poorly documented despite their increasing use. In the high-Arctic Archipelago of Svalbard, where marine mammals face increasing pressure from climate change and expanding tourism, the use of RPAS remains largely unregulated. In this study we assessed the impacts of RPAS across a range of species to provide science-based management advice, using a variety of aircraft sizes and approach strategies. We explored RPAS sound levels and animal behavior prior to and after flights. Preexperimental alertness influenced sensitivity to disturbance notably. Harbor seals were more sensitive during prebreeding than during molting, reacting at distances of 80 m, whereas walruses responded at distances

This is the peer reviewed version of the following article: Sánchez-Hernandez, J. & Amundsen. P.-A. (2018). Ecosystem type shapes trophic position and omnivory in fishes. Fish and Fisheries, 19(6), 1003-1015, which has been published in final form at https://doi.org/10.1111/faf.12308. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. The identification of patterns in ecological characteristics of organisms is a central challenge in macroecology with a growing research interest. The goal of this study was to establish whether patterns in trophic ecology (trophic position and omnivory) of fishes can be extended to an ecosystem dimension (freshwater vs. marine environments), based on the premise that differences in environmental and ecological conditions of aquatic ecosystems have a large influence on the feeding ecology of fishes. To elucidate any relationship between trophic ecology and ecosystem type, we compiled a database using a global data set for fishes (http://www.fishbase.org). The database included 5,426 species distributed in 53 orders based on three common feeding strategies (herbivory, filter‐feeding and predatory). Trophic position and omnivory increased from freshwater to marine ecosystems in filter‐feeding and predatory species. In herbivore species in contrast, omnivory decreased, whereas no statistically significant trends were found for trophic position, which may reflect a similar diet specialization on primary producers regardless of ecosystem type. These findings suggest that ecosystem type has a marked effect on trophic position and omnivory in fishes, but the impact depends on the type of feeding strategy. Prey availability, inherent feeding traits linked to the phylogenetic relatedness of species, ontogenetic effects, spatial variability (habitat‐related factors) and body size are considered as responsible factors for the observed patterns. Our findings demonstrate consistent patterns in trophic characteristics of organisms linked to ecosystem type and underline the usefulness of fishes as model organisms to test macroecology hypotheses.

Large‐scale alterations in marine ecosystems as a response to environmental and anthropogenic pressures have been documented worldwide. Yet, these are primarily investigated by assessing abundance fluctuations of a few dominant species, which inadequately reflect ecosystem‐wide changes. In addition, it is increasingly recognized that it is not species identity per se, but their traits that determine environmental responses, biological interactions and ecosystem functioning. In this study, we investigated long‐term, spatio‐temporal variability in trait composition across multiple organism groups to assess whether functional changes occur in a similar way across trophic levels and whether shifts in trait composition link to environmental change. We combined extensive trait datasets with long‐term surveys (30–40 yr) of four organism groups (phytoplankton, zooplankton, benthic invertebrates and fish) in three environmentally distinct areas of a large marine ecosystem. We found similar temporal trajectories in the community weighted mean trait time‐series of the different trophic groups, revealing ecosystem‐wide functional changes. The traits involved and their dynamics differed between areas, concurrent with climate‐driven changes in temperature and salinity, as well as more local dynamics in nutrients and oxygen. This finding highlights the importance of considering both global climate, as well as local external drivers when studying ecosystem changes. Using a multi‐trophic trait‐based approach, our study demonstrates the importance of integrating community functional dynamics across multiple trophic levels to capture ecosystem‐wide responses which could, ultimately, help moving towards a holistic understanding, assessment and management of marine ecosystems.

Metabarcoding is by now a well‐established method for biodiversity assessment in terrestrial, freshwater and marine environments. Metabarcoding data sets are usually used for α‐ and β‐diversity estimates, that is, interspecies (or inter‐MOTU) patterns. However, the use of hypervariable metabarcoding markers may provide an enormous amount of intraspecies (intra‐MOTU) information ‐ mostly untapped so far. The use of cytochrome oxidase (COI) amplicons is gaining momentum in metabarcoding studies targeting eukaryote richness. COI has been for a long time the marker of choice in population genetics and phylogeographic studies. Therefore, COI metabarcoding data sets may be used to study intraspecies patterns and phylogeographic features for hundreds of species simultaneously, opening a new field which we suggest to name metaphylogeography. The main challenge for the implementation of this approach is the separation of erroneous sequences from true intra‐MOTU variation. Here, we develop a cleaning protocol based on changes in entropy of the different codon positions of the COI sequence, together with co‐occurrence patterns of sequences. Using a data set of community DNA from several benthic littoral communities in the Mediterranean and Atlantic seas, we first tested by simulation on a subset of sequences a two‐step cleaning approach consisting of a denoising step followed by a minimal abundance filtering. The procedure was then applied to the whole data set. We obtained a total of 563 MOTUs that were usable for phylogeographic inference. We used semiquantitative rank data instead of read abundances to perform AMOVAs and haplotype networks. Genetic variability was mainly concentrated within samples, but with an important between‐seas component as well. There were inter‐group differences in the amount of variability between and within communities in each sea. For two species the results could be compared with traditional Sanger sequence data available for the same zones, giving similar patterns. Our study shows that metabarcoding data can be used to infer intra‐ and interpopulation genetic variability of many species at a time, providing a new method with great potential for basic biogeography, connectivity and dispersal studies, and for the more applied fields of conservation genetics, invasion genetics, and design of protected areas.

Source at: http://doi.org/10.1111/ecog.03443 Large-scale patterns in species diversity and community composition are associated with environmental gradients, but the implications of these patterns for food-web structure are still unclear. Here, we investigated how spatial patterns in food-web structure are associated with environmental gradients in the Barents Sea, a highly productive shelf sea of the Arctic Ocean. We compared food webs from 25 subregions in the Barents Sea and examined spatial correlations among food-web metrics, and between metrics and spatial variability in seawater temperature, bottom depth and number of days with ice cover. Several food-web metrics were positively associated with seawater temperature: connectance, level of omnivory, clustering, cannibalism, and high variability in generalism, while other food-web metrics such as modularity and vulnerability were positively associated with sea ice and negatively with temperature. Food-web metrics positively associated with habitat heterogeneity were: number of species, link density, omnivory, path length, and trophic level. This finding suggests that habitat heterogeneity promotes food-web complexity in terms of number of species and link density. Our analyses reveal that spatial variation in food-web structure along the environmental gradients is partly related to species turnover. However, the higher interaction turnover compared to species turnover along these gradients indicates a consistent modification of food-web structure, implying that interacting species may co-vary in space. In conclusion, our study shows how environmental heterogeneity, via environmental filtering, influences not only turnover in species composition, but also the structure of food webs over large spatial scales.

Source at https://doi.org/10.1002/ece3.3797. Accepted manuscript version, licensed CC BY-NC-ND 4.0. Arctic sea ice provides microhabitats for biota that inhabit the liquid‐filled network of brine channels and the ice–water interface. We used meta‐analysis of 23 published and unpublished datasets comprising 721 ice cores to synthesize the variability in composition and abundance of sea ice meiofauna at spatial scales ranging from within a single ice core to pan‐Arctic and seasonal scales. Two‐thirds of meiofauna individuals occurred in the bottom 10 cm of the ice. Locally, replicate cores taken within meters of each other were broadly similar in meiofauna composition and abundance, while those a few km apart varied more; 75% of variation was explained by station. At the regional scale (Bering Sea first‐year ice), meiofauna abundance varied over two orders of magnitude. At the pan‐Arctic scale, the same phyla were found across the region, with taxa that have resting stages or tolerance to extreme conditions (e.g., nematodes and rotifers) dominating abundances. Meroplankton, however, was restricted to nearshore locations and landfast sea ice. Light availability, ice thickness, and distance from land were significant predictor variables for community composition on different scales. On a seasonal scale, abundances varied broadly for all taxa and in relation to the annual ice algal bloom cycle in both landfast and pack ice. Documentation of ice biota composition, abundance, and natural variability is critical for evaluating responses to decline in Arctic sea ice. Consistent methodology and protocols must be established for comparability of meiofauna monitoring across the Arctic. We recommend to (1) increase taxonomic resolution of sea ice meiofauna, (2) focus sampling on times of peak abundance when seasonal sampling is impossible, (3) include the bottom 30 cm of ice cores rather than only bottom 10 cm, (4) preserve specimens for molecular analysis to improve taxonomic resolution, and (5) formulate a trait‐based framework that relates to ecosystem functioning.

Source at http://dx.doi.org/10.1002/lno.10519 Zooplankton vertical migration enhances the efficiency of the ocean biological pump by translocating carbon (C) and nitrogen (N) below the mixed layer through respiration and excretion at depth. We measured C and N active transport due to diel vertical migration (DVM) in a Svalbard fjord at 79°N. Multifrequency analysis of backscatter data from an Acoustic Zooplankton Fish Profiler moored from January to September 2014, combined with plankton net data, showed that Thysanoessa spp. euphausiids made up > 90% of the diel migrant biomass. Classical synchronous DVM occurred before and after the phytoplankton bloom, leading to a mismatch with intensive primary production during the midnight sun. Zooplankton DVM resulted in C respiration of 0.9 g m−2 and ammonium excretion of 0.18 g N m−2 below 82 m depth between February and April, and 0.2 g C m−2 and 0.04 g N m−2 from 11 August to 9 September, representing > 25% and > 33% of sinking flux of particulate organic carbon and nitrogen, respectively. Such contribution of DVM active transport to the biological pump in this high-Arctic location is consistent with previous measurements in several equatorial to subarctic oceanic systems of the World Ocean. Climate warming is expected to result in tighter coupling between DVM and bloom periods, stronger stratification of the Barents Sea, and northward advection of boreal euphausiids. This may increase the role of DVM in the functioning of the biological pump on the Atlantic side of the Arctic Ocean, particularly where euphausiids are or will be prevalent in the zooplankton community.

Source at https://doi.org/10.1002/ece3.4963. Ongoing changes along the northeastern Atlantic coastline provide an opportunity to explore the influence of climate change and multitrophic interactions on the recovery of kelp. Here, vast areas of sea urchin‐dominated barren grounds have shifted back to kelp forests, in parallel with changes in sea temperature and predator abundances. We have compiled data from studies covering more than 1,500‐km coastline in northern Norway. The dataset has been used to identify regional patterns in kelp recovery and sea urchin recruitment, and to relate these to abiotic and biotic factors, including structurally complex substrates functioning as refuge for sea urchins. The study area covers a latitudinal gradient of temperature and different levels of predator pressure from the edible crab (Cancer pagurus) and the red king crab (Paralithodes camtschaticus). The population development of these two sea urchin predators and a possible predator on crabs, the coastal cod (Gadus morhua), were analyzed. In the southernmost and warmest region, kelp forests recovery and sea urchin recruitment are mainly low, although sea urchins might also be locally abundant. Further north, sea urchin barrens still dominate, and juvenile sea urchin densities are high. In the northernmost and cold region, kelp forests are recovering, despite high recruitment and densities of sea urchins. Here, sea urchins were found only in refuge habitats, whereas kelp recovery occurred mainly on open bedrock. The ocean warming, the increase in the abundance of edible crab in the south, and the increase in invasive red king crab in the north may explain the observed changes in kelp recovery and sea urchin distribution. The expansion of both crab species coincided with a population decline in the top‐predator coastal cod. The role of key species (sea urchins, kelp, cod, and crabs) and processes involved in structuring the community are hypothesized in a conceptual model, and the knowledge behind the suggested links and interactions is explored.

This is the peer reviewed version of the following article: Hassett, B.T. & Gradinger, R. (2017). New Species of Saprobic Labyrinthulea (=Labyrinthulomycota) and the Erection of a gen. nov. to Resolve Molecular Polyphyly within the Aplanochytrids. Journal of Eukaryotic Microbiology, 65(4), 475-483. https://doi.org/10.1111/jeu.12494, which has been published in final form at https://doi.org/10.1111/jeu.12494. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. A culture of a unicellular heterotrophic eukaryote was established from pollen‐baited seawater acquired from the nearshore environment in Tromsø, Norway. Light microscopy revealed the production of ectoplasmic nets and reproduction by biflagellated zoospores, as well as binary division. After culturing and subsequent nucleotide extraction, database queries of the isolate's 18S small ribosomal subunit coding region identified closest molecular affinity to Aplanochytrium haliotidis, a pathogen of abalone. Testing of phylogenetic hypotheses consistently grouped our unknown isolate and A. haliotidis among the homoplasious thraustochytrids. Transmission electron microscopy revealed complex cell walls comprised of electron‐dense lamella that formed protuberances, some associated with bothrosomes. Co‐culturing experiments with the marine fungus Penicillium brevicompactum revealed prolonged interactions with hyphal strands. Based on the combined information acquired from electron microscopy, life history information, and phylogenetic testing, we describe our unknown isolate as a novel species. To resolve molecular polyphyly within the aplanochytrids, we erect a gen. nov. that circumscribes our novel isolate and the former A. haliotidis within the thraustochytrids.

Aim: Anticipated changes in the global ocean climate will affect the vulnerability of marine ecosystems to the negative effects of non-indigenous species (NIS). In the Arctic, there is a need to better characterize present and future marine biological introduction patterns and processes. We use a vector-based assessment to estimate changes in the vulnerability of a high-Arctic archipelago to marine NIS introduction and establishment. Location: Global, with a case study of Svalbard, Norway. Methods: We base our assessment on the level of connectedness to global NIS pools through the regional shipping network and predicted changes in ocean climates. Environmental match of ports connected to Svalbard was evaluated under present and future environmental conditions (2050 and 2100 predicted under the RCP8.5 emissions scenario). Risk of NIS introduction was then estimated based on the potential for known NIS to be transported (in ballast water or as biofouling), environmental match, and a qualitative estimate of propagule pressure. Results: We show that Svalbard will become increasingly vulnerable to marine NIS introduction and establishment. Over the coming century, sea surface warming at high latitudes is estimated to increase the level of environmental match to nearly one-third of ports previously visited by vessels travelling to Svalbard in 2011 (n = 136). The shipping network will then likely connect Svalbard to a much greater pool of known NIS, under conditions more favourable for their establishment. Research and fishing vessels were estimated to pose the highest risk of NIS introduction through biofouling, while ballast water discharge is estimated to pose an increased risk by the end of the century. Main conclusions: In the absence of focused preventative management, the risk of NIS introduction and establishment in Svalbard, and the wider Arctic, will increase over coming decades, prompting a need to respond in policy and action.

Source at http://dx.doi.org/10.1002/2016JC011779 This study compiles colocated oceanic observations of high-resolution vertical profiles of nitrate concentration and turbulent microstructure around the Svalbard shelf slope, covering both the permanently ice-free Fram Strait and the pack ice north of Svalbard. The authors present an overview over the seasonal evolution of the distribution of nitrate and its relation to upper ocean stratification. The average upward turbulent diffusive nitrate flux across the seasonal nitracline during the Arctic summer season is derived, with average values of 0.3 and 0.7 mmol m−2 d−1 for stations with and without ice cover, respectively. The increase under ice-free conditions is attributed to different patterns of stratification under sea ice versus open water. The nitrate flux obtained from microstructure measurements lacked a seasonal signal. However, bottle incubations indicate that August nitrate uptake was reduced by more than an order of magnitude relative to the May values. It remains inconclusive whether the new production was limited by an unidentified factor other than NO3− supply in late summer, or the uptake was underestimated by the incubation method.

Accepted manuscript version. Published version at http://doi.org/10.1111/jai.12792. The aim of this study was to compare somatic growth and muscle fibre development in diploid and triploid siblings of Atlantic cod (Gadus morhua Linnaeus, 1758) during the larval stage. Newly hatched larvae were transferred into 200-L tanks, three tanks per ploidy group (70 larvae L−1, continuous light, gradually increasing seawater temperature 7–11°C and flow rates 50–117 L h−1). Larvae were fed rotifers from 2 to 22 days post hatch (dph), Artemia 19–31 dph and weaned onto a microparticulate diet from 26 dph until the end of the experiment. Measurements of growth (dry weight, standard length) and muscle cellullarity were taken at intervals between 1 and 44 dph. Ploidy groups showed a similar performance throughout the trial, although a marked stagnation in growth was observed for triploids during the weaning from Artemia onto dry feed. Overall, diploid and triploid cod larvae showed a similar development in muscle fibre growth pattern during the experimental period. For both groups, the total number of fast muscle fibres showed a 10-fold increase (from 384 to 3462), whereas the diameter of fast fibre increased from 8.9 to 13.3 μm (mean number from all treatments). Thus, a temporary but significant effect of triploidy on fast muscle fibre growth pattern was observed in 19 dph larvae in terms of fibre size and number, with triploids showing larger mean fast fibre diameter (11.62 ± 0.63 vs. 10.05 ± 0.34) and a lower number of fibres with a diameter

Accepted manuscript version. Published version at http://doi.org/10.1111/are.12879. This study has investigated the muscle growth of diploid and triploid Atlantic cod (Gadus morhua) juveniles raised in replicate tanks over a period of 29 weeks and analysed at three sampling points (February, June and September). Data for weight, length, condition factor (K), muscle fibre growth and myogenic progenitor cells (MPCs) number were collected and results were analysed in relation to body growth and ploidy status. Diploids were significantly heavier than triploids throughout the trial (~10–20%) and had K in June and September samplings. Over the whole period, the rate of muscle fibres’ recruitment was 318 fibres per day and 252 fibres per day for diploid and triploid cod respectively. The larger body weight of diploids resulted in a total num- ber of fast fibre number of 114 979 compared to 91 086 in triploids. The average diameter of the 2.5% of the smallest fibres (2.5th percentile) was higher in diploids than triploids at the start of the trial, with a reversed picture for the aver- age of the upper 2.5% (97.5th percentile) at the end of the trial. The probability density function of the estimated muscle fibre diameters showed similar fibre size distribution between size- matched diploids and triploids at all sample points. The peak fibre diameter was approxi- mately 25 lm in February and increased to approximately 50 lm in June and September, irrespectively of ploidy. Pax 7 were used as molecular markers for MPCs. A positive correla- tion between Pax 7+ cells and total body length was observed only among triploid fish at the onset of the experiment.

This is the peer reviewed version of the following article: Amundsen, P.-A., Siwertsson, A-, Primicerio, R. & Bøhn, T. (2009). Long-term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourse. Freshwater Biology, 54, 24-34, which has been published in final form at https://doi.org/10.1111/j.1365-2427.2008.02088.x. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. 1. Introduced or invading predators may have strong impacts on prey populations of the recipient community mediated by direct and indirect interactions. The long‐term progression of predation effects, covering the invasion and establishment phase of alien predators, however, has rarely been documented. 2. This paper documents the impact of an invasive, specialized planktivorous fish on its prey in a subarctic watercourse. Potential predation effects on the crustacean plankton, at the community, population and individual levels, were explored in a long‐term study following the invasion by vendace (Coregonus albula). 3. Over the 12‐year period, the density and species richness of zooplankton decreased, smaller species became more abundant and Daphnia longispina, one of the largest cladocerans, was eliminated from the zooplankton community. 4. Within the dominant cladocerans, including Daphnia spp., Bosmina longispina and Bosmina longirostris, the body size of ovigerous females and the size at first reproduction decreased after the arrival of the new predator. The clutch sizes of Daphnia spp. and B. longirostris also increased. 5. Increased predation pressure following the vendace invasion induced many effects on the crustacean zooplankton, and we document comprehensive and strong direct and indirect long‐term impacts of an introduced non‐native predator on the native prey community.