Search results for "VDP::Landbruks- og Fiskerifag: 900"
showing 10 items of 67 documents
Influence of larval transport and temperature on recruitment dynamics of North Sea cod (Gadus morhua) across spatial scales of observation
2020
The survival of fish eggs and larvae, and therefore recruitment success, can be critically affected by transport in ocean currents. Combining a model of early‐life stage dispersal with statistical stock–recruitment models, we investigated the role of larval transport for recruitment variability across spatial scales for the population complex of North Sea cod (Gadus morhua). By using a coupled physical–biological model, we estimated the egg and larval transport over a 44‐year period. The oceanographic component of the model, capable of capturing the interannual variability of temperature and ocean current patterns, was coupled to the biological component, an individual‐based model (IBM) tha…
Population structure in Atlantic cod in the eastern North Sea-Skagerrak-Kattegat: early life stage dispersal and adult migration
2016
Background In marine fish species, where pelagic egg and larvae drift with ocean currents, population structure has been suggested to be maintained by larval retention due to hydrographic structuring and by homing of adult fish to natal areas. Whilst natal homing of adults has been demonstrated for anadromous and coral reef fishes, there are few documented examples of philopatric migration in temperate marine fish species. Results Here, we demonstrate temporally stable genetic differentiation among spawning populations of Atlantic cod (Gadus morhua L.), and present genetic and behavioural evidence for larval drift and philopatric migration in the eastern North Sea-Skagerrak-Kattegat area. W…
Compositional and morphological analyses of wax in northern wild berry species.
2019
Accepted manuscript version, licensed CC BY-NC-ND 4.0. Aerial surfaces of plants are covered by a waxy cuticle protecting plants from excessive water loss and UV light. In the present study, composition and morphology of cuticular waxes of northern wild berry species bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.), bog bilberry (V. uliginosum L.) and crowberry (Empetrum nigrum L.) were investigated. Scanning electron microscopy (SEM) revealed differences in epicuticular wax morphology, and gas chromatography–mass spectrometry (GC–MS) analysis confirmed variation in chemical composition of cuticular waxes between the berry species. The dominant compounds in bilberry and li…
Applying Artificial Intelligence Methods to Detect and Classify Fish Calls from the Northern Gulf of Mexico
2021
Passive acoustic monitoring is a method that is commonly used to collect long-term data on soniferous animal presence and abundance. However, these large datasets require substantial effort for manual analysis
Disparate movement behavior and feeding ecology in sympatric ecotypes of Atlantic cod
2021
Abstract Coexistence of ecotypes, genetically divergent population units, is a widespread phenomenon, potentially affecting ecosystem functioning and local food web stability. In coastal Skagerrak, Atlantic cod (Gadus morhua) occur as two such coexisting ecotypes. We applied a combination of acoustic telemetry, genotyping, and stable isotope analysis to 72 individuals to investigate movement ecology and food niche of putative local “Fjord” and putative oceanic “North Sea” ecotypes—thus named based on previous molecular studies. Genotyping and individual origin assignment suggested 41 individuals were Fjord and 31 were North Sea ecotypes. Both ecotypes were found throughout the fjord. Seven …
Attuning to a changing ocean
2020
The ocean is a lifeline for human existence, but current practices risk severely undermining ocean sustainability. Present and future social−ecological challenges necessitate the maintenance and development of knowledge and action by stimulating collaboration among scientists and between science, policy, and practice. Here we explore not only how such collaborations have developed in the Nordic countries and adjacent seas but also how knowledge from these regions contributes to an understanding of how to obtain a sustainable ocean. Our collective experience may be summarized in three points: 1) In the absence of long-term observations, decision-making is subject to high risk arising from na…
Movement patterns of temperate wrasses (Labridae) within a small marine protected area
2021
The movement patterns of three commercially important wrasse (Labridae) species inside a small marine protected area (~ 0.15 km2 ) on the west coast of Norway were analysed over a period of 21 months. The mean distance between capture and recapture locations varied between 10 and 187 m, and was species and season specific. The extent of movement was not related to body size or sex. These results imply that a network of small strategically located marine protected areas can be used as management tools to protect wrasses from size- and sex-selective fishing mortality.
Kartlegging av vandringshindre og kvantifisering av europeisk ål (Anguilla anguilla) ved bruk av miljø-DNA
2019
Masteroppgave akvatisk økologi BIO500 - Universitetet i Agder 2019 Europeaneel (Anguilla anguilla) is an endangered species nationally and internationally, and the EU-Commissionhas decided that conservation effort is needed. One of the challenges in Norway is obstacles in migration routes, especially where riversareput in pipes underneath roads. In addition, knowledge regarding biomass is essential in conservation work. In this study, environmental DNA (eDNA) has been investigated as a tool for mapping migration obstaclesfor eel.The possibility of usingindividual differences in eDNAto separate individuals, as an estimation of biomass, was also investigated. eDNA is DNA that organisms shed t…
Kartlegging av laks og ørret i kystvassdrag i Agder ved studier av miljø-DNA
2021
Master's thesis in Coastal ecology (BIO501) Both Atlantic salmon (Salmo salar) and Brown trout (Salmo trutta) spawn in freshwaters, and availability to water courses of good water quality is of great importance for the Salmonidae populations. The industrial revolution introduced release of considerable amounts of sulphur and nitrogen taken up by the environments, including aquatic habitats. Through the 20thcentury, the pH levels dramatically dropped while levels of toxic aluminium rose in the freshwaters. The acidic and toxic waters strongly affected the salmon populations, and several of the stocks of south Norwegian rivers were eliminated. The trout, however, have managed the decrease in …
Responses of European lobster (Homarus gammarus) and lobster fishers to protective management
2017
Master's thesis Aquatic Ecology BIO500 - University of Agder 2017 Marine protected areas (MPAs) are valued for their conservation benefits to harvested species. However, potential benefits of MPAs to neighboring fisheries are less well-understood. This study quantifies how the European lobster (Homarus gammarus) and the fishery for this valued catch respond to the establishment of a relatively small (5.2 km2) MPA on the Norwegian Skagerrak coast. A series of yearly standardized trap surveys was conducted to estimate lobster abundance and catch weights both inside and outside the MPA before (2010- 2011) and after the MPA was established (2012-2016). Lobster abundance and catch weights were d…