Search results for "VDP::Mathematics and natural science: 400::Zoology and botany: 480::Marine biology: 497"
showing 10 items of 15 documents
Resource polymorphism in European whitefish: Analysis of fatty acid profiles provides more detailed evidence than traditional methods alone
2019
Published version, licensed CC BY-NC-ND 4.0. , available at: http://dx.doi.org/10.1371/journal.pone.0221338 Resource polymorphism—whereby ancestral generalist populations give rise to several specialised morphs along a resource gradient—is common where species colonise newly formed ecosystems. This phenomenon is particularly well documented in freshwater fish populations inhabiting postglacial lakes formed at the end of the last ice age. However, knowledge on how such differential exploitation of resources across contrasting habitats might be reflected in the biochemical compositions of diverging populations is still limited, though such patterns might be expected. Here, we aimed to assess …
Resource Partitioning in Food, Space and Time between Arctic Charr (Salvelinus alpinus), Brown Trout (Salmo trutta) and European Whitefish (Coregonus…
2017
Arctic charr and European whitefish are considered to be strong competitors in lakes, with the latter usually being the superior species. However, high niche plasticity and lake morphometry may suggestively facilitate resource partitioning and coexistence between charr and whitefish. Here, we explore the trophic niche utilization (diet and habitat use) of charr and whitefish co-occurring with brown trout in the deep and oligotrophic Lake Fyresvatnet, southern Norway (59˚05’N, 8˚10’E). Using CPUE, stomach contents and stable isotope analyses, a distinct resource partitioning was revealed between brown trout and the other two species. Brown trout typically occupied the littoral zone, feeding …
Northern refugia and recent expansion in the North Sea: The case of the wrasse Symphodus melops (Linnaeus, 1758)
2011
Pleistocene climate changes have imposed extreme conditions to intertidal rocky marine communities, forcing many species to significant range shifts in their geographical distributions. Phylogeographic analyses based on both mitochondrial and nuclear genetic markers provide a useful approach to unravel phylogeographic patterns and processes of species after this time period, to gain general knowledge of how climatic changes affect shifts in species distributions. We analyzed these patterns on the corkwing wrasse (Symphodus melops, Labridae), a rocky shore species inhabiting North Sea waters and temperate northeastern Atlantic Ocean from Norway to Morocco including the Azores, using a fragme…
Community structure affects trophic ontogeny in a predatory fish.
2016
While most studies have focused on the timing and nature of ontogenetic niche shifts, information is scarce about the effects of community structure on trophic ontogeny of top predators. We investigated how community structure affects ontogenetic niche shifts (i.e., relationships between body length, trophic position, and individual dietary specialization) of a predatory fish, brown trout (Salmo trutta). We used stable isotope and stomach content analyses to test how functional characteristics of lake fish community compositions (competition and prey availability) modulate niche shifts in terms of (i) piscivorous behavior, (ii) trophic position, and (iii) individual dietary specialization. …
Arctic sea ice algae differ markedly from phytoplankton in their ecophysiological characteristics
2021
Photophysiological and biochemical characteristics were investigated in natural communities of Arctic sea ice algae and phytoplankton to understand their respective responses towards variable irradiance and nutrient regimes. This study revealed large differences in photosynthetic efficiency and capacity between the 2 types of algal assemblages. Sea ice algal assemblages clearly displayed increased photoprotective energy dissipation under the highest daily average irradiance levels (>8 µmol photons m-2 s-1). In contrast, phytoplankton assemblages were generally light-limited within the same irradiance ranges. Furthermore, phytoplankton assemblages exhibited more efficient carbon assimilat…
Lobster and cod benefit from small-scale northern marine protected areas: inference from an empirical before - after control-impact study
2013
Published version of an article from the journal: Proceedings of the Royal Society B-Biological Sciences. Alsop available from the Royal Society: http://dx.doi.org/10.1098/rspb.2012.2679 Open Access Marine protected areas (MPAs) are increasingly implemented as tools to conserve and manage fisheries and target species. Because there are opportunity costs to conservation, there is a need for science-based assessment of MPAs. Here, we present one of the northernmost documentations of MPA effects to date, demonstrated by a replicated before-after control-impact (BACI) approach. In 2006, MPAs were implemented along the Norwegian Skagerrak coast offering complete protection to shellfish and parti…
Natural selection against offshore Atlantic cod (Gadus morhua) in Skagerrak fjords?
2016
Master's thesis Aquatic Ecology BIO500 - University of Agder 2016 The marine environment was previously presumed to be demographically “open”, and marineorganisms were thought to have pronounced gene flow over vast areas due to their potentialof dispersal during early life stages. However, recent studies have suggested a degree of selfrecruitmentwithin segments of coastal and offshore areas for several marine species. Two ofthe forces acting on this structuring are retention of early life stages and homing of adultindividuals. This study looks at the distribution of early life stages of the Atlantic cod (Gadusmorhua) in two Norwegian fjords divided into inshore-offshore transects, and study…
Analysering av miljø-DNA for kartlegging av marin fiskefauna
2016
Masteroppgave akvatisk økologi BIO500 - Universitetet i Agder 2016 Marine ecosystems worldwide are currently threatened due to overfishing and other humanimpacts. To monitor marine fish, which represents a main component in present monitoring ofmarine ecosystem health, one is mainly depending on invasive and selective methods. Thesemethods are also dependent on physical identification of species, which in many cases can bedifficult, or in some cases, impossible. Such limitations of traditional surveillance methodshave created a demand for alternative methods. One such alternative is the environment-DNAmethod, i.e. analysis of genetic material from a sample collected in the environment.In th…
Socializing makes thick-skinned individuals: on the density of epidermal alarm substance cells in cyprinid fish, the crucian carp (Carassius carassiu…
2010
Published version of an article in the journal: Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. Also available on SpringerLink: http://dx.doi.org/10.1007/s00359-010-0550-4 In cyprinid fish, density of epidermal club cells (i.e. alarm substance cells) has been found to vary between lakes with different predator fauna. Because predators can be labelled with chemical cues from prey, we questioned if club cell density could be controlled indirectly by predators releasing prey cues. In particular, we suspected a possible feedback mechanism between chemical alarm signals and their cellular source. We raised crucian carp singly and in groups of four.…
Challenging fear: chemical alarm signals are not causing morphology changes in crucian carp (Carassius carassius)
2010
Published version of an article in the journal: Environmental Biology of Fishes. Also available at SpringerLink: http://dx.doi.org/10.1007/s10641-010-9707-9 Crucian carp develops a deep body in the presence of chemical cues from predators, which makes the fish less vulnerable to gape-limited predators. The active components originate in conspecifics eaten by predators, and are found in the filtrate of homogenised conspecific skin. Chemical alarm signals, causing fright reactions, have been the suspected inducers of such morphological changes. We improved the extraction procedure of alarm signals by collecting the supernatant after centrifugation of skin homogenates. This removes the minute …