Search results for "VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480"
showing 10 items of 87 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…
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…
Home range and excursive post-breeding movements of Eurasian Eagle-owls revealed by GPS satellite transmitters
2021
Investigating space use of wild birds provides important knowledge of bird behavior and ecology, which is crucial in the management and conservation of threatened species. In the present study, we used GPS satellite telemetry to investigate space use and movements of seven adult Eurasian Eagle-Owls (Bubo bubo) in Norway during breeding and post-breeding seasons. Breeding adults had a mean home range size of 42.9 km2 (SD ± 35.1 km2; 95% kernel density estimation Had hoc), and five individuals performed long (>20 km) excursive movements away from their breeding territories during autumn. Such wide-ranging behavior has not previously been reported for adults of the nominate subspecies B. b. bu…
Network measures in animal social network analysis : Their strengths, limits, interpretations and uses
2020
International audience; We provide an overview of the most commonly used social network measures in animal research for static networks or time‐aggregated networks. For each of these measures, we provide clear explanations as to what they measure, we describe their respective variants, we underline the necessity to consider these variants according to the research question addressed, and we indicate considerations that have not been taken so far. We provide a guideline indicating how to use them depending on the data collection protocol, the social system studied and the research question addressed. Finally, we inform about the existent gaps and remaining challenges in the use of several va…
Protection from fishing improves body growth of an exploited species
2022
Hunting and fishing are often size-selective, which favours slow body growth. In addition, fast growth rate has been shown to be positively correlated with behavioural traits that increase encounter rates and catchability in passive fishing gears such as baited traps. This harvest-induced selection should be effectively eliminated in no-take marine-protected areas (MPAs) unless strong density dependence results in reduced growth rates. We compared body growth of European lobster ( Homarus gammarus ) between three MPAs and three fished areas. After 14 years of protection from intensive, size-selective lobster fisheries, the densities in MPAs have increased considerably, and we demonstrate t…