| 1. |
- Näslund, Joacim, et al.
(författare)
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Considerations needed for analysing data from the Swedish Electrofishing RegiSter (SERS), with special reference to the RivFishTIME database of long-term riverine surveys
- 2023
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Ingår i: Fauna Norvegica. - 1502-4873 .- 1891-5396. ; 42, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- The published database RivFishTIME (Comte et al. 2021, Global Ecology and Biogeography, doi: 10.1111/geb.13210) includes a large section of time-series data on fish abundance in Swedish rivers from the Swedish Electrofishing RegiSter, SERS. Knowledge about the limitations of the source data are important when extracting and analyzing data and with this brief note we provide some details that may be helpful for interpreting the Swedish time-series. The note highlights the importance of linking vital metadata to extracted focal data when constructing new databases, especially concerning time series data from monitoring programs conducted in non-randomly selected sites with human environmental impacts. Many of the SERS data come from rivers that have been affected by human impact, e.g. liming to mitigate environmental acidification and hydropower dams, since before monitoring was initiated. Data in SERS are also biased towards shallow salmonid habitats, due to the configuration of Swedish monitoring programs. Hence, data from many rivers are not representative of their fish biodiversity in general. This information is vital for appropriate interpretation of fish biodiversity trends. For RivFishTIME analyses considerations are important since Swedish data constitutes a large proportion of the database. We also provide background information about SERS and references to other Swedish databases containing complementary information. Finally, we provide contact information of the SERS database curators, who can assist prospective analysts with data extraction from SERS.
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| 2. |
- Axenrot, Thomas, et al.
(författare)
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Ontogenetic variation in lacustrine European smelt (Osmerus eperlanus) populations as a response to ecosystem characteristics : an indicator of population sensitivity to environmental and climate stressors
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Smelts play a key role in the pelagic ecosystem of large lakes in northern Europe and North America. In numbers, they often dominate the open water. In large lakes in Scandinavia (including Finland), European smelt (Osmerus eperlanus L.), a cold-water glacial relict, is commonly the most important prey for piscivorous fish species, but also acts by ontogenetic shifts as a predator on zoo-plankton, small crustaceans, fish larvae, mysids and occasionally – with increasing size - fish. Furthermore, the large numbers of smelt in the open water are important competitors to other planktivorous fish. Due to the diverse life histories and biological interactions of smelt in large lakes, its role in the food-web structure is expected to be variable. Smelt population dynamics, recruitment, size and age structure, growth, life history and mortality were analysed and compared for five Swedish lakes that varied in size, depth, morphology, trophic status and latitude to understand the varying life histories and roles in lake food-webs. The results showed that in shallow, eutrophic lakes smelt stayed small and short-lived, and populations experienced high mortality. In deeper, colder and less nutrient-rich lakes, smelts grew larger and older, and might shift to a piscivorous trophic level. By ontogenetic adaptions smelt seems to uphold high abundance and recruitment over a wide range of ecosystems, but in shallow lakes without cold water refuges smelt populations run the risk of collapsing on the occasion of extremely warm summers with drastic consequences for their predators and lake ecosystems.
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| 3. |
- Axenrot, Thomas, et al.
(författare)
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Seasonal variation in thermal habitat volume for cold-water fish populations : implications for hydroacoustic survey design and stock assessment
- 2023
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Rapport (refereegranskat)abstract
- For accurate stock assessment, survey design must consider fish behavior and ecology. Yearlings and older individuals of the commercially exploited cold-water species vendace (Coregonus albula) are found below the metalimnion through periods of thermal stratification. These stratification periods generally last for 3-4 months, from the middle of summer to early autumn. In lakes with heterogeneous distribution of depths, the habitat volume for vendace vary drastically within and across years, which affects the distribution and population densities. Variable thermal habitat volumes, with food and oxygen depletion in the hypolimnion through the period of stratification, may act as a population size-regulating factor.Using hydroacoustics in combination with trawl data and temperature profiles, we examined the distribution of vendace through annual periods of thermal stratification. We found that yearling and older vendace these periods were confined to cold-water habitat volumes representing less than 10 % of the total water volume of Lake Mälaren, the third largest lake in Sweden. By introducing stratification to the design of hydroacoustic surveys supported by midwater trawling, seasonal aggregations of fish in temporally restricted thermal habitat volumes can be used to lower survey effort and improve the precision in estimates of population size. Temporally restricted habitat volumes may induce risks for the populations to over-fishing and sensitivity to environmental changes that potentially may call for directed management.
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| 4. |
- Bovinder Ylitalo, Erik, et al.
(författare)
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A novel DNA methylation signature is associated with androgen receptor activity and patient prognosis in bone metastatic prostate cancer
- 2021
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Ingår i: Clinical Epigenetics. - : BioMed Central. - 1868-7083 .- 1868-7075. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Patients with metastatic prostate cancer (PC) are treated with androgen deprivation therapy (ADT) that initially reduces metastasis growth, but after some time lethal castration-resistant PC (CRPC) develops. A better understanding of the tumor biology in bone metastases is needed to guide further treatment developments. Subgroups of PC bone metastases based on transcriptome profiling have been previously identified by our research team, and specifically, heterogeneities related to androgen receptor (AR) activity have been described. Epigenetic alterations during PC progression remain elusive and this study aims to explore promoter gene methylation signatures in relation to gene expression and tumor AR activity.Materials and methods: Genome-wide promoter-associated CpG methylation signatures of a total of 94 tumor samples, including paired non-malignant and malignant primary tumor areas originating from radical prostatectomy samples (n = 12), and bone metastasis samples of separate patients with hormone-naive (n = 14), short-term castrated (n = 4) or CRPC (n = 52) disease were analyzed using the Infinium Methylation EPIC arrays, along with gene expression analysis by Illumina Bead Chip arrays (n = 90). AR activity was defined from expression levels of genes associated with canonical AR activity.Results: Integrated epigenome and transcriptome analysis identified pronounced hypermethylation in malignant compared to non-malignant areas of localized prostate tumors. Metastases showed an overall hypomethylation in relation to primary PC, including CpGs in the AR promoter accompanied with induction of AR mRNA levels. We identified a Methylation Classifier for Androgen receptor activity (MCA) signature, which separated metastases into two clusters (MCA positive/negative) related to tumor characteristics and patient prognosis. The MCA positive metastases showed low methylation levels of genes associated with canonical AR signaling and patients had a more favorable prognosis after ADT. In contrast, MCA negative patients had low AR activity associated with hypermethylation of AR-associated genes, and a worse prognosis after ADT.Conclusions: A promoter methylation signature classifies PC bone metastases into two groups and predicts tumor AR activity and patient prognosis after ADT. The explanation for the methylation diversities observed during PC progression and their biological and clinical relevance need further exploration.
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| 5. |
- Donadi, Serena, et al.
(författare)
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Contrasting long-term trends in juvenile abundance of a widespread cold-water salmonid along a latitudinal gradient: effects of climate, stream size and migration strategy
- 2023
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587.
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Tidskriftsartikel (refereegranskat)abstract
- A changing climate reshapes the range distribution of many organisms, and species with relatively low thermal optima, like many salmonids, are increasingly expected to face local population extinctions at lower latitudes. Understanding where and how fast these changes are happening is of pivotal importance for successful mitigation and conservation efforts.We used an extensive electrofishing database to explore temporal trends of juveniles of brown trout Salmo trutta in 218 locations from 174 Swedish streams, over the last 30 years (1991-2020). We hypothesized that 1) declines in abundance have occurred predominately in the warmer, southern regions, while increases have occurred in the colder, northern regions, 2) larger stream sizes may partly offset negative effects of climate, and 3) migrating and resident populations are affected differently by a warming climate.We found that abundance of brown trout juveniles generally declined in warmer regions especially in smaller streams (<= 6 m wide), while the abundance increased in colder regions. In larger streams, negative effects of higher temperatures were seemingly buffered, as we found lower rates of decline or even positive trends. The rate of change (i.e. the slopes of the trends in abundance) was more pronounced towards the climate extremes, and was on average zero in regions with a normal annual air temperature (average temperature over 30 year period) around 5-6 degrees C. Warmer climate had stronger effects on migrating compared to resident populations, suggesting that climate-induced loss of stream connectivity could be an additional factor that hinders recruitment in anadromous populations in a changing climate.Considering predictions of increasing temperatures and frequency of summer droughts, management of cold-water salmonid populations should focus on conserving and restoring riparian vegetation, wetlands, climate and thermal refugia, and habitat integrity overall. Such measures may, however, not suffice for small streams at lower latitudes, unless hydrological connectivity is maintained.
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| 6. |
- Donadi, Serena, et al.
(författare)
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Interactive effects of land use, river regulation, and climate on a key recreational fishing species in temperate and boreal streams
- 2021
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 66, s. 1901-1914
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Tidskriftsartikel (refereegranskat)abstract
- Numerous anthropogenic stressors, including river regulation, excess loadings of nutrients and sediment, channelisation, as well as thermal and hydrological stressors driven by climate change impact riverine ecosystems worldwide. In a time when freshwater degradation and the rate of global warming are faster than ever, understanding the potential interactive effects of local and catchment-scale stressors with large-scale climatic conditions is essential to enhance our ability to plan effective conservation, restoration, and mitigation measures. In this study we analysed a dataset spanning the whole of Sweden using a space-for-time approach to investigate interactive effects of land use, river regulation, and climate on brown trout (Salmo trutta) abundance in streams. We found that in warmer regions trout populations were negatively affected in catchments with more intense river regulation by hydropower dams (i.e. >= 10 m(3)/km(2) total reservoir storage volume). In such catchments, a 7 degrees C warmer mean summer air temperature was associated with an average between 44% and 83% decline in trout abundance. In catchments with less intense river regulation, trout abundance instead increased moderately with increasing temperature. We also found that brown trout abundance declined with increasing areal extent of urban areas when found in combination with >= 20% agricultural land use. When agricultural land use reached maximum values (84%), brown trout abundance decreased from an average of 13 individuals per 100 m(2) in catchments with no urban areas to values <= 1 in catchments with >= 5% urban land use. Also, brown trout abundance declined with increasing agricultural land use in catchments with >= 3% urban land use. Our study brings innovative empirical evidence of interactive effects between river regulation, land use and climate on brown trout populations. From a management perspective our findings suggest that: (1) restoring natural flows (e.g. through dam removal) and riparian vegetation could mitigate adverse effects of climate change; and (2) restoration measures that minimise the effects of agriculture and urban land use (e.g. reduction of nutrient levels and restored riparian buffer zones) could help rehabilitate brown trout in catchments with high anthropogenic land use change. However, given the large observed variation between streams, we advise for bespoke management actions stemming from sound knowledge of local habitat conditions and target populations, whenever possible, using an ecosystem management-based approach.
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| 7. |
- Hegmar, Hannes, et al.
(författare)
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Liver stiffness predicts progression to liver-related events in patients with chronic liver disease - A cohort study of 14 414 patients
- 2024
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Ingår i: Liver international. - : WILEY. - 1478-3223 .- 1478-3231.
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: Liver stiffness measurement (LSM) by vibration-controlled transient elastography (VCTE) is a non-invasive diagnostic biomarker of liver fibrosis. It is uncertain if LSM can predict risk for future liver-related outcomes in large, heterogenous populations. Methods: This Swedish multi-centre cohort study included patients (n = 14 414) from 16 sites who underwent LSM by VCTE between 2008 and 2020. Outcomes were ascertained from national registers. We investigated progression to cirrhosis with portal hypertension or hepatocellular carcinoma (HCC), separately. Cox regression was used to obtain hazard ratios (HRs). Harrel's C-index was used to measure discrimination of VCTE. Results: Included patients had a median age of 46 (interquartile range 34-57), median LSM of 5.9 kPa (4.6-8.0), 59% were male, and the majority had hepatitis C (50.1%). During a median follow-up of 5.9 (4.3-8.0) years, 402 patients (2.7%) developed cirrhosis with portal hypertension. In patients with an LSM >= 25 kPa, 28.7% developed cirrhosis with portal hypertension within 5 years of follow-up, while only .6% of patients with an LSM <10 kPa did. This translated to a HR of 48.3 (95% confidence interval = 37.6-62.0). VCTE had a high discriminative ability, with C-indices above .80 for most liver diseases, including .82 for MASLD. Similar findings were seen for incident HCC. Conclusions: Increased LSM by VCTE was associated with an increased risk of progression to both cirrhosis with portal hypertension, and to HCC, and had a high discriminative ability across different aetiologies of chronic liver diseases. These results support the use of VCTE to guide follow-up and treatment decisions.
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| 8. |
- Nilsson, Per Anders, 1968-, et al.
(författare)
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Substrate-size choice in European eel (Anguilla anguilla) elvers is not altered by piscivore chemical cues
- 2020
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Ingår i: Journal of Fish Biology. - : John Wiley & Sons. - 0022-1112 .- 1095-8649. ; 96:6, s. 1534-1537
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Tidskriftsartikel (refereegranskat)abstract
- The European eel Anguilla anguilla Linnaeus 1758 is critically endangered with recruitment estimated at 5-10% of historical levels. Enhancing survival of recruits is pivotal for conservation, and restoration should consider habitat choice of elvers ascending river systems. We experimentally show that newly ascended elvers choose small pebble habitat over finer and larger substrates, regardless of the presence or absence of piscivore chemical cues, indicating no predator-induced change in substrate choice. Enriching habitats with this substrate fraction should enhance eel recruitment as well as biodiversity at large.
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| 9. |
- Näslund, Joacim, et al.
(författare)
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Negative influence of a threatened species on ecological status classification: A case study of the influence of European eel within the Swedish fish index VIX
- 2022
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 144
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Tidskriftsartikel (refereegranskat)abstract
- Biological indicators are important quality elements for classification of ecological status of water bodies ac-cording to the European Water Framework Directive. Multimetric indices are commonly regarded as robust and reliable indicators of human impact and are often used as quality elements. In fish-based indices, species are often grouped into guilds based on general tolerance to common anthropogenic pressures, with higher pro-portion of tolerant species being indicative of degraded systems. Within the Swedish electrofishing index VIX, the critically endangered European eel Anguilla anguilla (L.) is classified as a tolerant indicator species, and it therefore has a negative effect on classified ecological status. The scientific literature, however, suggests that eels are not generally tolerant and they benefit from similar environmental conditions as many insensitive species. VIX has been criticized for being too sensitive to the presence of eel in catch data, leading to low status clas-sifications when eels are caught in the monitoring surveys. In a case study using manipulations of historical electrofishing data, we assessed the influence of eel presence and abundance on the ecological status classifi-cation as determined by VIX. We demonstrate that reduction of eels in survey data have positive effects on the classified status, in many cases substantial effects. An increase of eels in the data had the reverse effect. Mere presence of eel had a strong negative effect, which is problematic if the aim is to increase the endangered eel population. Given the Swedish classification system where the quality element indicating the worst status is decisive, the classified ecological status of Swedish rivers can theoretically be improved by management actions disfavouring eel, unless the results from VIX are carefully evaluated by experts. Along the same lines, measures implemented with an aim to increase the endangered eel population will lead to a decrease in assessed ecological status of Swedish rivers. Our conclusion is that the usage of VIX within Swedish water management is prob-lematic and needs revision. From a broader perspective, the classification of species as generally tolerant need to be approached with great caution when developing new indices for assessing ecological status and integrity.
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| 10. |
- Tamario, Carl, et al.
(författare)
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Ecological marginality and recruitment loss in the globally endangered freshwater pearl mussel
- 2022
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Ingår i: Journal of Biogeography. - : John Wiley & Sons. - 0305-0270 .- 1365-2699. ; 49:10, s. 1793-1804
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Tidskriftsartikel (refereegranskat)abstract
- Aim Ecological marginality is the existence of species/populations in the margins of their ecological niche, where conditions are harsher, and the risk of extinction is more pronounced. In threatened long-lived species, the disparity between distribution and population demography may provide understanding of how environmental heterogeneity shapes ecological marginality, potential extinction patterns and range shifts. We set out to evaluate this by combining a species distribution model (SDM) with population-specific demography data. Location Sweden, 450,000 km(2). Major Taxa Studied Freshwater pearl mussel (FPM, Margaritifera margaritifera) and two salmonid fish species. Methods A SDM for the mussel was constructed with MaxEnt using salmonid host fish (Salmo trutta plus S. salar) density, extreme low and high temperatures, precipitation, altitude, and clay content as explanatory variables. The output was used to test the ecological marginality hypothesis by evaluating whether lowly predicted populations had higher loss of recruitment. Logistic regression was used to explicitly test the factors involved in recruitment loss. Results Host fish density contributed the most (50.3%) to the mussel distribution, followed by lowest temperature the coldest month (34.3%) and altitude (10.3%), while the remaining explanatory variables contributed minimally (<3.3%). Populations with lower SDM scores lacked recruitment to a significantly higher degree. Populations inhabiting areas at low altitude, with lower densities of host fish, and warmer winter temperatures have lost recruitment to a higher degree. Main Conclusions We found support for the ecological marginality hypothesis. The patterns indicate that FPM habitat niche may shift northwards over time. Salmonid host fish density seems to be a driving factor for both historical distribution and recent demographic performance. Finally, we emphasize the value of combining SDMs with independent data on population demography as it both lends rigidity to model validation and understanding of how ecological marginality affects species distribution and viability.
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