Change search
Refine search result
1 - 7 of 7
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ahlbeck, Ida
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Evaluating fish diet analysis methods by individual-based modelling2012In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 69, no 7, p. 1184-1201Article in journal (Refereed)
    Abstract [en]

    Knowledge of diet compositions is important in ecological research. There are many methods available and numerous aspects of diet composition. Here we used modelling to evaluate how well different diet analysis methods describe the true diet of fish, expressed in mass percentages. The methods studied were both basic methods (frequency of occurrence, dominance, numeric, mass, points) and composite indices (Index of Relative Importance, Comparative Feeding Index). Analyses were based on both averaged stomach content of individual fish and on pooled content from several fish. Prey preference, prey size, and evacuation rate influenced the performance of the diet analysis methods. The basic methods performed better than composite indices. Mass and points methods produced diet compositions most similar to the true diet and were also most robust, indicating that these methods should be used to describe energetic-nutritional sources of fish.

  • 2.
    Ahlbeck, Ida
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Evaluation of diet analysis methods by individual based modellingIn: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533Article in journal (Refereed)
  • 3. Carlström, Julia
    et al.
    Berggren, Per
    Stockholm University, Faculty of Science, Department of Zoology.
    Tregenza, Nick
    Spatial and temporal impact of pingers on porpoises2009In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 66, no 1, p. 72-82Article in journal (Refereed)
    Abstract [en]

     

    Bycatches are considered the most serious threat to harbour porpoises (Phocoena phocoena) and other small cetaceans worldwide. Pingers are used to reduce bycatch levels, but may also deter porpoises from critical habitats. We investigated the spatial and temporal responses of porpoises to simulated bottom-set nets equipped with periodically operating Dukane NetMark 1000 pingers. Echolocation rates were monitored by porpoise click train detectors (PODs) placed at and around the nets, and a shore-based observation team recorded surfacing positions and movements. Pinger sound significantly reduced the median echolocation encounter rate by 50%–100% at PODs placed up to 500 m and reduced the sighting rate up to 375 m from the simulated net. The average distance of approach increased by 300 m. When pingers were silent after being active for 24 h 50 min, the return time of porpoises was 6 h, in comparison with 2.5 h after pingers had been silent. During the study period of approximately 50 days, habituation was detectable at two of nine PODs. The results indicate that pingers affect porpoises at greater distances than previously observed. This confirms that pingers are an effective bycatch mitigation measure, but alternative solutions should be applied in ecologically important habitats and migration routes. An example is given from the Baltic region.

     

     

    Bycatches are considered the most serious threat to harbour porpoises and other small cetaceans worldwide.  Pingers are used to reduce bycatch levels, but may also deter porpoises from critical habitats.  We investigated the spatial and temporal responses of porpoises to simulated bottom set nets equipped with periodically operating Dukane NetMark 1000 pingers.  Echolocation rates were monitored by porpoise click train detectors (PODs) placed at and around the nets, and a shore-based observation team recorded surfacing positions and movements.  Pinger sound significantly reduced the median echolocation encounter rate by 50-100% at PODs placed up to 500m, and the sighting rate up to 375m from the simulated net.  The average distance of approach increased by 300m.  When pingers were silent after being active for 24h 50min, the return time of porpoises was 6h, in comparison to 2.5h after pingers had been silent.  During the study period of approximately 50 days, habituation was detectable at two of nine PODs.  The results indicate that pingers affect porpoises at greater distances than previously observed.  This confirms that pingers are an effective bycatch mitigation measure, but alternative solutions should be applied in ecologically important habitats and migration routes. An example is given from the Baltic region.

     

  • 4. Dekker, Willem
    et al.
    Sjöberg, Niklas B.
    Institute for Freshwater Research, Swedish University of Agricultural Sciences, Sweden.
    Assessment of the fishing impact on the silver eel stock in the Baltic using survival analysis2013In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 70, no 12, p. 1673-1684Article in journal (Refereed)
    Abstract [en]

    Restoration of the depleted stock of the European eel (Anguilla anguilla (L.)) requires anthropogenic impacts to bequantified, reduced, and controlled. In this article, we assess the impact of the silver eel fishery on the Baltic Coast in Sweden, applying survival analysis to 60 years of mark–recapture experiments, involving 8000 recaptures out of 18 000 releases. Thehazard of being recaptured (overall 46%) varies along the coast and declined substantially over the decades. But, most notably,the hazard for the individual diminishes strongly after the first kilometres en route. This individualized hazard disqualifies themore traditional mark–recapture methodology, which assumes random recaptures. We advocate the general use of survivalanalysis for conventional mark–recapture data. The result of our analysis indicates that the impact of the fishery just prior the2009 fishing restrictions was in the order of 10%—in itself well within sustainability limits, though only but one of the factors contributing to the mortality in the Baltic Sea.

  • 5.
    Perry, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Staveley, Thomas A. B.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hammar, Linus
    Meyers, Alyssa
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Temperate fish community variation over seasons in relation to large-scale geographic seascape variables2018In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 75, no 10, p. 1723-1732Article in journal (Refereed)
    Abstract [en]

    In shallow-water marine environments, ecosystem functioning is a complex interworking of fine-scale characteristics and region-wide factors, and the importance of these variables can vary on multiple temporal and spatial scales. This underwater video study targeted seasonal changes in the fish community of seagrass habitats along the Swedish west coast and the influence of offshore seascape variables (latitudinal position, wave exposure, open ocean, and deep water). Results showed that fish assemblage structure exhibited seasonal changes between summer and autumn and strong spatiotemporal variations in the importance of offshore factors affecting shallow-water fish communities. In summer, abundance from the Gobiidae family responded to wave exposure, whereas the Gadidae family and juvenile migrant habitat preference guild responded to latitudinal position and proximity to deep water. In autumn, deep water was related to abundance of Gadidae and juvenile migrants, whereas latitudinal position influenced Gasterosteidae. These findings underscore the importance of understanding the influence of offshore factors on facets of coastal fish assemblages to address large-scale geographic connectivity along nearshore–offshore gradients.

  • 6.
    Sundberg, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Ishaq, Rasha
    Tjärnlund, Ulla
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Åkerman, Gun
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Grunder, Kerstin
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bandh, Cecilia
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Broman, Dag
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Balk, Lennart
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Contribution of commonly analyzed polycyclic aromatic hydrocarbons (PAHs) in sediment to potential toxicity in early life-stages of rainbow trout (Oncorhynchus mykiss)2006In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 63, no 6, p. 1320-1333Article in journal (Refereed)
    Abstract [en]

    In a series of bio-effect-directed fractionation experiments, we investigated the potential toxicity of sediment extracts from a contaminated bay. A previous study investigated abnormalities and hepatic ethoxyresorufin O-deethylase (EROD) activities in rainbow trout (Oncorhynchus mykiss) larvae by exposing newly fertilized eggs to the total extract and to fractions separated by degree of aromaticity. A major part of the potential toxicity was isolated in a fraction containing polycyclic aromatic compounds (PACs). In this study, we prepared a synthetic PAC mixture with 17 commonly analyzed polycyclic aromatic hydrocarbons (PAHs) in amounts equimolar to those found in the sediment PAC fraction. The 17 PAHs, which included 11 of the 16 United States Environmental Protection Agency (US EPA) priority PAHs, were unable to account for the toxicopathic effects observed and could explain less than 4% of the total EROD induction. The lack of a clear relationship between toxicopathic effects and EROD induction underlines the need for a battery of biomarkers for estimating environmental risk. These results reveal the limits of our knowledge regarding compounds responsible for potential toxicity in field situations.

  • 7.
    Wennerström, Lovisa
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Olsson, Jens
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology.
    Laikre, Linda
    Stockholm University, Faculty of Science, Department of Zoology.
    Temporally stable, weak genetic structuring in brackish water northern pike (Esox lucius) in the Baltic Sea indicates a contrasting divergence pattern relative to freshwater populations2017In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 74, no 4, p. 562-571Article in journal (Refereed)
    Abstract [en]

    Understanding spatiotemporal population genetic patterns is important for conservation management of ecologically and socioeconomically important species. This is particularly so in species-poor environments such as the brackish Baltic Sea. We examined over 600 northern pike (Esox lucius), a coastal predator and treasured sport fish, collected over major parts of the Baltic Sea coastline. We found low genetic divergence among populations, indicating a contrasting genetic structure of brackish water coastal spawners compared with previous reports on anadromous Baltic pike migrating up freshwater streams for spawning. A pattern of genetic isolation by distance either over shortest waterway or primarily along the mainland coast with islands as stepping stones suggested that gene flow is primarily taking place among neighboring populations, possibly with some migration over open water. Temporal data showed a stable genetic structure over a decade. Within a single sampling year, however, spatial divergence was larger during spawning than feeding season, indicating increased mixing of populations during the feeding season. Management should assure connectivity among brackish spawning grounds and large population sizes at identified core areas.

1 - 7 of 7
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf