Search results for "VDP::Landbruks- og Fiskerifag: 900"
showing 10 items of 67 documents
Atlantic salmon survival at sea: temporal changes that lack regional synchrony
2022
Spatial and temporal synchrony in abundance or survival trends can be indicative of whether populations are affected by common environmental drivers. In Atlantic salmon (Salmo salar L.), return rates to natal rivers have generally been assumed to be affected primarily by shared oceanic conditions, leading to spatially synchronous trends in mortality. Here, we investigated the existence of parallel trends in salmon sea survival, using data on migrating smolts and returning adults from seven Canadian populations presumed to share feeding grounds. We analysed sea survival, using a Bayesian change-point model capable of detecting non-stationarity in time series data. Our results indicate that w…
Catchability and selectivity in a multispecies wrasse fishery in Western Norway
2020
Master's thesis in Coastal ecology (BIO501) Goldsinny(Ctenolabrus rupestris), corkwing(Symphodus melops)and ballan wrasse(Labrus bergylta) are heavily harvested on the west coast of Norway because of their delousing ability andare supplied to the aquaculture industry as a key tool incontrollingsalmon lice infestations. Despite rapid development of the fishery in the past decade, knowledge on catchabilityand selectivity in this multispecies fisheryis still limited. This information is essential to ensure sustainable harvesting levels and developing good management strategies for wrasse.In a before-after control-impact (BACI) study, passive integrated transmitter (PIT) tags wereused to monito…
Assessing the impacts of marine protected areas on wrasse populations in Norway
2020
Master's thesis in Coastal ecology (BIO501)
Bacterial diversity within and outside the premises of a South Norwegian salmon fish farm
2021
Master's thesis in Coastal ecology (BIO501) Norwegian salmon farming is a rapidly expanding sector and the Norwegian Government have a set goal to facilitate a five-fold growth towards 2050. Organic enrichment of the surrounding waters and the sediment below the cages due to the inputs of organic matter from uneaten food, tissue and faecal matter etc., affect the macro -and microfauna. To monitor the effect of these organic inputs, fish breeding companies must perform periodic controls. Traditionally, these periodic controls are based on time-consuming and expensive methods, and the necessary taxonomic knowledge is declining. In this study, we evaluated the usefulness of marine bacterial co…
Incorporating intra-annual variability in fisheries abundance data to better capture population dynamics
2022
Abstract To reduce the risk of overexploitation and the ensuing conservation and socio-economic consequences, fisheries management relies on receiving accurate scientific advice from stock assessments. Biomass dynamics models used in stock assessment tend to rely primarily on indices of abundance and commercial landings data. Standard practice for calculating the indices used in these models typically involves taking averages of survey tow data over large, diverse spatial domains. There is a lot of variability in the choice of methodologies used to propagate index uncertainty into the assessment model, many of which require specifying it through expert knowledge or prior distributions. Here…
Climate mitigation and intensified forest management in Norway: To what extent are surface waters safeguarded?
2020
AbstractWhile the role of forestry in mitigating climate change is increasingly subject to political commitment, other areas, such as water protection, may be at risk. In this study, we ask whether surface waters are sufficiently safeguarded in relation to the 2015 launch of a series of measures to intensify forest management for mitigation of climate change in Norway. First, we assess how impacts on water are accounted for in existing regulations for sustainable forestry. Secondly, we provide an overview of the impacts of forestry on water quality relevant to three support schemes: afforestation on new areas, increased stocking density in existing forests, and forest fertilisation. Lastly,…
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…
Stabilizing selection on Atlantic cod supergenes through a millennium of extensive exploitation
2022
Life on Earth has been characterized by recurring cycles of ecological stasis and disruption, relating biological eras to geological and climatic transitions through the history of our planet. Due to the increasing degree of ecological abruption caused by human influences many advocate that we now have entered the geological era of the Anthropocene, or “the age of man.” Considering the ongoing mass extinction and ecosystem reshuffling observed worldwide, a better understanding of the drivers of ecological stasis will be a requisite for identifying routes of intervention and mitigation. Ecosystem stability may rely on one or a few keystone species, and the loss of such species could potentia…
Streamwater responses to reduced nitrogen deposition at four small upland catchments in Norway
2020
AbstractReduced emissions of nitrogen (N) in Europe have resulted in decreasing atmospheric deposition since 1990. Long-term data (1988–2017) from four small Norwegian catchments located along gradients in N deposition, rainfall, and organic carbon (C) show different responses to 25–30% reductions in N deposition during the same period. At three sites the decreased N deposition caused reduced leaching of nitrate to surface water, whereas the westernmost site showed no decrease, probably due to thin soils with low C:N ratio, poor vegetation cover and high precipitation. The loss of total N to streamwater constituted 30–50% of the N deposition. Losses via denitrification are unknown but assum…
Design and verification of a solar powered automatic rooftop hydroponic system with real time individual measuring of potassium and calcium
2019
Master's thesis Renewable Energy ENE500 - University of Agder 2019 This report covers development and implementation of two hydroponic systems. One at a lab inside theUniversity of Agder, and one at the roof on the J-Building at the University. This report tries to answer thefollowing main research question: How can an automated system for control of nutrient concentration andpH in a solar powered hydroponic system be developed, implemented and verified?The focus of the report has been to create a fully functional system for the lab, generating data forelectronic conductivity for measuring a specter of nutrients, pH value, individual nutrients and temperaturefor comparison. The work has bee…