Browsing Brage IMR by Author "Handegard, Nils Olav"
Now showing items 21-40 of 84
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Data interoperability between elements of the global ocean observing system
Snowden, Derrick P.; Tsontos, Vardis; Handegard, Nils Olav; Zarate, Marcos; O'Brien, Kevin M.; Casey, Kenneth S.; Smith, Neville; Sagen, Helge; Bailey, Kathleen; Lewis, Mirtha; Arms, Sean (Journal article; Peer reviewed, 2019)The data management landscape associated with the Global Ocean Observing System is distributed, complex, and only loosely coordinated. Yet interoperability across this distributed landscape is essential to enable data to ... -
A deep learning-based method to identify and count pelagic and mesopelagic fishes from trawl camera images
Allken, Vaneeda; Rosen, Shale Pettit; Handegard, Nils Olav; Malde, Ketil (Peer reviewed; Journal article, 2021)Fish counts and species information can be obtained from images taken within trawls, which enables trawl surveys to operate without extracting fish from their habitat, yields distribution data at fine scale for better ... -
Deep Semi-Supervised Semantic Segmentation in Multi-Frequency Echosounder Data
Choi, Changkyu; Kampffmeyer, Michael; Jenssen, Robert; Handegard, Nils Olav; Salberg, Arnt-Børre (Peer reviewed; Journal article, 2023)Multi-frequency echosounder data can provide a broad understanding of the underwater environment in a non-invasive manner. The analysis of echosounder data is, hence, a topic of great importance for the marine ecosystem. ... -
Deep Semi-Supervised Semantic Segmentation in Multi-Frequency Echosounder Data
Choi, Changkyu; Kampffmeyer, Michael; Jenssen, Robert; Handegard, Nils Olav; Salberg, Arnt-Børre (Peer reviewed; Journal article, 2023)Multi-frequency echosounder data can provide a broad understanding of the underwater environment in a non-invasive manner. The analysis of echosounder data is, hence, a topic of great importance for the marine ecosystem. ... -
Designing an Ocean Mid-trophic Automatic Acoustic Sampler (MAAS) - thoughts on how to include echo sounder observatories in ecosystem models
Handegard, Nils Olav; Domokos, Réka; Godø, Olav Rune; Jouanno, Julien; Kloser, Rudy; Lehodey, Patrick; Maury, Olivier; Senina, Inna (ICES CM documents;2009/I:21, Working paper, 2009)Echo sounders are a widely used tool for observing marine ecosystems. Traditionally, carefully designed surveys are used to integrate biomass to a global estimate, which is coupled to traditional stock assessment models. ... -
Designing an Ocean Mid-trophic Automatic Acoustic Sampler(MAAS) –thoughts on how to include echo sounder observatories in ecosystem models
Handegard, Nils Olav; Godø, Olav Rune; Kloser, Rudy; Lehodey, Patrick; Maury, Olivier (Conference object, 2010-02) -
Detection, Localization and Classification of Multiple Mechanized Ocean Vessels over Continental-Shelf Scale Regions with Passive Ocean Acoustic Waveguide Remote Sensing
Zhu, Chenyang; Garcia, Heriberto; Kaplan, Anna; Schinault, Matthew; Handegard, Nils Olav; Godø, Olav Rune; Huang, Wei; Ratilal, Purnima (Journal article; Peer reviewed, 2018)Multiple mechanized ocean vessels, including both surface ships and submerged vehicles, can be simultaneously monitored over instantaneous continental-shelf scale regions >10,000 km 2 via passive ocean acoustic waveguide ... -
Diversity and seasonal development of large zooplankton along physical gradients in the Arctic Barents Sea
Engeland, Tom Van; Bagøien, Espen; Wold, Anette; Cannaby, Heather Anne; Majaneva, Sanna Kristiina; Vader, Anna; Rønning, Jon S.; Handegard, Nils Olav; Dalpadado, Padmini; Ingvaldsen, Randi Brunvær (Peer reviewed; Journal article, 2023)Due to ongoing climate change, a new Arctic Ocean ecosystem is emerging. Within the framework of the Nansen Legacy project, we investigated the community composition of the large zooplankton and its seasonal development ... -
Effects on individual level behaviour in mackerel (Scomber scombrus) of sub-lethal capture related stressors: Crowding and hypoxia
Anders, Neil; Howarth, Kirsten; Totland, Bjørn; Handegard, Nils Olav; Tenningen, Maria; Breen, Michael (Journal article; Peer reviewed, 2019)Stress to fish during harvest in wild capture fisheries is known to negatively influence subsequent survival in catches that are released. Therefore, if fisheries are to be conducted sustainably, there is a need to promote ... -
Effects on schooling function in mackerel of sub-lethal capture related stressors: Crowding and hypoxia
Handegard, Nils Olav; Tenningen, Maria; Howarth, Kirsten; Anders, Neil; Rieucau, Guillaume; Breen, Michael (Journal article; Peer reviewed, 2017)The selectivity of fishing gears with respect to fish species and size is important, both for fisheries management and fishing operations. Purse seining is an efficient, environmentally friendly fish capture methodology ... -
Effekter av seismiske undersøkelser på fiskefordeling og fangstrater for garn og line i Vesterålen sommeren 2009 : Effects of seismic surveys on fish distribution and catch rates of gillnets and longlines in Vesterålen in summer 2009
Løkkeborg, Svein; Ona, Egil; Vold, Aud; Peña, Hector; Salthaug, Are; Totland, Bjørn; Øvredal, Jan Tore; Dalen, John; Handegard, Nils Olav (Fisken og havet, Research report, 2010-02-22)In connection with the Norwegian Petroleum Directorate’s seismic survey off the coasts of Vesterålen in summer 2009, a project was carried out to study the degree to which commercial fishes were affected. Four chartered ... -
Estimating tail-beat frequency using split-beam echosounders
Handegard, Nils Olav; Pedersen, Geir; Brix, Ole (Journal article; Peer reviewed, 2009-02-04)Data from a standard split-beam echosounder are used to estimate tail-beat frequency within a dense herring (Clupea harengus L.) layer. The data were collected by lowering a horizontally projecting 38 kHz split-beam ... -
Estimating tail-beat frequency using split-beam echosounders
Handegard, Nils Olav; Pedersen, Geir; Brix, Ole (Journal article; Peer reviewed, 2009-02-04)Data from a standard split-beam echosounder are used to estimate tail-beat frequency within a dense herring (Clupea harengus L.) layer. The data were collected by lowering a horizontally projecting 38 kHz split-beam ... -
Evaluating acoustic-trawl survey strategies using an end-to-end ecosystem model
Holmin, Arne Johannes; Mousing, Erik Askov; Skogen, Morten D.; Hjøllo, Solfrid Sætre; Huse, Geir; Handegard, Nils Olav (Peer reviewed; Journal article, 2020)Fisheries independent surveys support science and fisheries assessments but are costly. Evaluating the efficacy of a survey before initiating it could save costs. We used the NORWECOM.E2E model to simulate Northeast Atlantic ... -
Evaluating the effect of seismic surveys on fish — the efficacy of different exposure metrics to explain disturbance
Handegard, Nils Olav; Tronstad, Tron Vedul; Hovem, Jens Martin (Journal article; Peer reviewed, 2013-06-05)To assess potential disturbance effects on fish from seismic air-gun surveys, we described several metrics to characterize the exposures from such surveys, including the number of emissions by area and time, and metrics ... -
Evaluation of echosounder data preparation strategies for modern machine learning models
Ordonez, Alba; Utseth, Ingrid; Brautaset, Olav; Korneliussen, Rolf; Handegard, Nils Olav (Peer reviewed; Journal article, 2022)Fish stock assessment and management requires accurate estimates of fish abundance, which are typically derived from echosounder observations using acoustic target classification (ATC). Skilled operators are regularly ... -
Experimental evidence of threat-sensitive collective avoidance responses in a large wild-caught herring school
Rieucau, Guillaume; Boswell, Kevin M.; De Robertis, Alex; Macaulay, Gavin; Handegard, Nils Olav (Peer reviewed; Journal article, 2014)Aggregation is commonly thought to improve animals’ security. Within aquatic ecosystems, group-living prey can learn about immediate threats using cues perceived directly from predators, or from collective behaviours, for ... -
Experimental Evidence of Threat-Sensitive Collective Avoidance Responses in a Large Wild-Caught Herring School
Rieucau, Guillaume; Boswell, Kevin M.; De Robertis, Alex; Macaulay, Gavin J.; Handegard, Nils Olav (Journal article; Peer reviewed, 2014-01-29)Aggregation is commonly thought to improve animals' security. Within aquatic ecosystems, group-living prey can learn about immediate threats using cues perceived directly from predators, or from collective behaviours, for ... -
Final report for the REDUS project - Reduced Uncertainty in Stock Assessment
Olsen, Erik Joel Steinar; Aanes, Sondre; Aldrin, Magne Tommy; Breivik, Olav Nikolai; Fuglebakk, Edvin; Goto, Daisuke; Handegard, Nils Olav; Hansen, Cecilie; Holmin, Arne Johannes; Howell, Daniel; Johnsen, Espen; Jourdain, Natoya; Korsbrekke, Knut; Ono, Kotaro; Otterå, Håkon Magne; Perryman, Holly Ann; Subbey, Samuel; Søvik, Guldborg; Umar, Ibrahim; Vatnehol, Sindre; Vølstad, Jon Helge (Rapport fra havforskningen;2021 - 16, Research report, 2021)The REDUS project (2016-2020) has been a strategic project at the Institute of Marine Research (IMR) aimed at quantifying and reducing the uncertainty in data-rich and age-structured stock assessments (e.g., cod, herring, ... -
Fish avoidance of research vessels and the efficacy of noise-reduced vessels: a review
De Robertis, Alex; Handegard, Nils Olav (Journal article; Peer reviewed, 2012-10-19)It has long been recognized that fish can avoid approaching vessels and that these behaviours can bias fishery surveys. Underwater noise is considered the primary stimulus, and standards for research vessel noise have been ...