Search results for "400"
showing 10 items of 1272 documents
Feeding Ecology of Harbour Seals (Phoca vitulina) in Southern Norway
2017
Master's thesis Aquatic Ecology BIO500 - University of Agder 2017 In order to understand ecosystem dynamics and functions it is vital to have knowledge about relationships between predator and prey. Harbour seals (Phoca vitulina) are piscivorous marine mammals found at or near the top of marine food webs. Being mainly piscivores, harbour seals have the potential to come into conflict with fishermen and fisheries. Recently, as the Skagerrak and Kattegat population of harbour seals has increased, claims that seals are depleting the cod population have surfaced. Using scat sampling and otolith identification, harbour seal diet was estimated in four separate locations along the coast of souther…
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…
Assessing the impacts of marine protected areas on wrasse populations in Norway
2020
Master's thesis in Coastal ecology (BIO501)
Homing Ability of Goldsinny Wrasse (Ctenolabrus rupestris)
2021
Master's thesis in Coastal ecology (BIO501) After the discovery of delousing abilities of temperate wrasses, several wrasse species are increasingly harvested in Norway and supplied to salmonid aquafarms to combat sea lice infestations. An increased harvesting intensity has raised concerns regarding the sustainability of this comparatively new fishery. Therefore, more research is needed about the targeted wrasses species. Goldsinny wrasses (Ctenolabrus rupestris)are known for having small home ranges and being highly territorial. Minimum size restrictions oblige fishermen to release goldsinnies smaller than 11 cm back to the sea, but this is often done far from the capture site. It is very …
Visual fish assemblage inventory of outer Oslo fjord, with special emphasis on young-of-the-year Atlantic cod (Gadus morhua)
2021
Master's thesis in Coastal ecology (BIO501) The coastal zone along the outer Oslofjord is physically unique and home to many ecologically depleted and economically important species, including Atlantic cod (Gadus morhua). Coastal cod in Skagerrak is divided into two ecotypes that co-exist in outer Oslofjord. Remnant local populations are considered sensitive to climate disturbances and anthropogenic influences. Recruitment of cod in Skagerrak is monitored in the annual beach seine sampling. A strong year-class of cod recruited to nursery areas in outer Oslo fjord in 2017. Although recruitment of cod has been monitored extensively in Skagerrak, studies have only recently begun to examine the…
Long term effects of activated carbon on benthic communities
2021
Master's thesis in Coastal ecology (BIO501) Thin-layer capping with activated carbon (AC) has a potential as situ remediation method for sediments exposed to hydrophobic organic compounds (HOCs). This treatment was applied at two test fields; one in the Eidangerfjord (95 m) and the other in the Ormerfjord (30 m) in 2009. These two fjords are a part of the Grenland fjord system which have a long history of contaminated sediments. In this study we will address long-term effects of thin-layer capping with AC on the benthic community nine years later. Number of individuals, species and biomass was significantly reduced in both test fields compared to their corresponding reference fields. The di…
Methods for studying coastal bivalves in a changing world : A review and implications for management
2021
Master's thesis in Coastal ecology (BIO501) Anthropogenic activities such as pollution, CO2 emission, and overfishing, are among leading reasons for global environmental change and negative impacts on the marine environment including loss of biodiversity. Marine bivalves are an example of species that suffers from such consequences while they have high value in both aquaculture and marine ecosystems. With the existence of many threats including overharvesting, invasive species, parasites, and diseases, coastal bivalves such as flat oysters (Ostrea edulis) and blue mussels (Mytilus spp) are in many places endangered. The existing knowledge gaps in the historic and current distribution, howev…
Do cold-water corals spatially correlate with submarine canyons in the Bay of Biscay? : A GIS study analysing the spatial distribution of cold-water …
2020
Master's thesis in Coastal ecology (BIO501) The seascape of the Bay of Biscay is a mysterious place. It is located to the west of France and the north of Spainand is often defined as well-differentiated geomorphological unit. The continental margin of the BoB is incised with many submarine canyons and is also thought to be a hotspot for cold-water corals.Unfortunately, it is an area under high anthropogenic pressure where intense fishing activity, bottom trawling especially, is causing major disturbances to benthic habitats such as cold-water corals. Cold-water corals have been well studied along the European margin and have more frequently been recorded in the northeastAtlantic than any ot…
Tick-borne pathogens in Ixodes ricinus ticks collected from migratory birds in southern Norway
2020
Birds are important hosts for the first life stages of the Ixodes ricinus tick and they can transport their parasites over long distances. The aim of this study was to investigate the prevalence of Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Neoehrlichia mikurensis and Rickettsia helvetica in ticks collected from migratory birds in Norway. A total of 815 Ixodes ricinus ticks from 216 birds trapped at Lista Bird Observatory in southern Norway during spring and autumn migration in 2008 were analysed by real-time PCR. B. burgdorferi s. l. was the most prevalent pathogen, detected in 6.1% of the ticks. The prevalence of N. mikurensis, A. phagocytophilum and R. helvetica was 1.2%…