Browsing Brage IMR by Author "Vølstad, Jon Helge"
Now showing items 1-20 of 33
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A framework for improving accuracy in fisheries data used in stock assessments
Pennington, Michael; Vigneau, Joel; Helle, Kristin; Vølstad, Jon Helge (ICES CM documents;2008/N:27, Working paper, 2009) -
A method for estimating dredge catching efficiency for blue crabs, Callinectes sapidus, in Chesapeake Bay
Vølstad, Jon Helge; Sharov, Alexei F.; Davis, Glenn; Davis, Brenda (Journal article; Peer reviewed, 2000)A winter dredge survey of blue crab (Callinectes sapidus Rathbun) is conducted annually in Chesapeake Bay as a key element of a longterm, bay-wide population dynamics study. Removal experiments are performed routinely as ... -
Abundance Estimation and Population Dynamics of the Blue Crab in the Chesapeake Bay : Final Report
Vølstad, Jon Helge; Rothschild, Brian J.; Maurer, T. (Research report, 1994-01) -
Adaptive management of living marine resources by integrating different data sources and key ecological processes (ADMAR): A joint effort by IMR and CEES
Handegard, Nils Olav; Stenseth, Nils Christian; Dankel, Dorothy Jane; Durant, Joël M.; Eikeset, Anne Maria; Enberg, Katja; Hjermann, Dag Ø.; Huse, Geir; Pennington, Michael; Skern-Mauritzen, Mette; Stige, Leif Christian; Subbey, Samuel; Vølstad, Jon Helge (ICES CM documents;2010/R:26 Poster;, Working paper, 2010-09) -
An evaluation of survey design for estimating the food consumption by fish
Bogstad, Bjarte; Pennington, Michael; Vølstad, Jon Helge (ICES CM Documents;1991/D:15, Working paper, 1991)The effect of survey design on the precision of estimates of average fish stomach contents is examined. The contribution to the total variance from within and between tow variability in stomach contents is evaluated, ... -
Analysis of spatial variability of Georges Bank haddock (Melanogrammus aeglefinus) from trawl survey data using a linear regression model with spatial interaction
Polacheck, Tom; Vølstad, Jon Helge (ICES CM Documents;1990/D:36, Working paper, 1990)A regression model with spatially autocorrelated errors is used to test if there is systematic spatial variation across the study area in haddock catch per tow data from the NEFC annual fall survey from 1963 - 1987. A ... -
Analytical and statistical review of procedures for collection and analysis of commercial fishery data used for management and assessment of groundfish stocks in the U.S. exclusive economic zone off Alaska
Vølstad, Jon Helge; Richkus, W.A.; Gaurin, Steve; Easton, Robert (Research report, 1997)Effective management of multi-species fisheries requires reliable estimates of the amount and composition of catch and bycatch. In this report, we present the results of analyses of observer program data ... -
Assessing incidental bycatch of seabirds in Norwegian coastal commercial fisheries: Empirical and methodological lessons
Fangel, Kirstin; Aas, Øystein; Vølstad, Jon Helge; Bærum, Kim Magnus; Christensen-Dalsgaard, Signe; Nedreaas, Kjell Harald; Overvik, Modolf; Wold, Line Camilla; Anker-Nilssen, Tycho (Journal article; Peer reviewed, 2015-06-23)Unintentional bycatch, waterbirds, small vessel fishery, gillnetts, longlines, Northeast Atlantic -
Assessing the effect of intra-haul correlation and variable density on population estimates from marine surveys
Pennington, Michael; Vølstad, Jon Helge (ICES CM Documents;1991/D:14, Working paper, 1991)In a previous paper (Pennington and Vølstad, Biometrics 47, 1991) it was suggested that reducing the size of the sampling unit generally used in marine surveys could increase the precision of abundance estimates. But if ... -
The Coastal Reference Fleet 2007-2019 - Fleet composition, fishing effort and contributions to science
Hatlebrekke, Hanne Hjelle; Gundersen, Sofie; Nedreaas, Kjell Harald; Vølstad, Jon Helge; Kolding, Jeppe (Rapport fra havforskningen;2021 - 52, Research report, 2021)Catch quotas are used for the sustainable management of fish stocks and are based on official catch statistics and research surveysSustainable management of the Norwegian fisheries depends on quota advice that is based on ... -
CPUE trends of Hilsa kelee and Thryssa vitrirostris exploited by the artisanal finfish fisheries in Mozambique derived from an on-shore sampling of catches by trip
Cardinale, Massimiliano; Chacate, Osvaldo; Casini, Michele; Chauca, Isabel; Vølstad, Jon Helge (Journal article; Peer reviewed, 2014-03)Artisanal fisheries are often overlooked by fisheries management agencies despite their great importance for food security and livelihoods. The assessment and management of those fisheries is often rare, especially in ... -
Dive to survive: effects of capture depth on barotraumaand post-release survival of Atlantic cod (Gadus morhua)in recreational fisheries
Ferter, Keno; Weltersbach, Marc Simon; Humborstad, Odd Børre; Fjelldal, Per Gunnar; Sambraus, Florian; Strehlow, Harry Vincent; Vølstad, Jon Helge (Journal article; Peer reviewed, 2015-06-04)Atlantic cod (Gadus morhua) caught in recreational fisheries are commonly released, often with barotrauma after rapid decompression. Mouth-hooked, non-bleeding cod kept in a floating net pen showed mortalities ≥40% when ... -
Effects of Fishing Tourism in a Coastal Municipality: a Case Study from Risør, Norway
Moksness, Erlend; Gjøsæter, Jakob; Lagaillarde, Guillaume; Mikkelsen, Eirik; Olsen, Esben Moland; Sandersen, Håkan T.; Vølstad, Jon Helge (Journal article; Peer reviewed, 2011)Recreational fishing has become an important part of the Norwegian tourist industry. The coastal municipality of Risør, southern Norway, is considering further development of its marine fishing tourism to increase local ... -
Effects of Fishing Tourism in a Coastal Municipality: a Case Study from Risør, Norway
Moksness, Erlend; Gjøsæter, Jakob; Lagaillarde, Guillaume; Mikkelsen, Eirik; Olsen, Esben Moland; Sandersen, Håkan T.; Vølstad, Jon Helge (Journal article; Peer reviewed, 2011)Recreational fishing has become an important part of the Norwegian tourist industry. The coastal municipality of Risør, southern Norway, is considering further development of its marine fishing tourism to increase local ... -
Estimation of annual mortality rates for eastern oysters (Crassostrea virginica) in Chesapeake Bay based on box counts and application of those rates for projection of population growth of both C. virginica and the Asian oyster (C. ariakensis)
Vølstad, Jon Helge; Dew, J.R.; Tarnowski, Mitchell (Journal article; Peer reviewed, 2008-08)In an effort to restore the ecological role of oysters in Chesapeake Bay and the economic benefits of a commercial fishery, the states of Maryland and Virginia are considering introducing the nonnative Asian oyster ... -
Estimation of annual mortality rates for eastern oysters (Crassostrea virginica) in Chesapeake Bay based on box counts and application of those rates for projection of population growth of both C. virginica and the Asian oyster (C. ariakensis)
Vølstad, Jon Helge; Dew, J.R.; Tarnowski, Mitchell (Journal article; Peer reviewed, 2008-08)In an effort to restore the ecological role of oysters in Chesapeake Bay and the economic benefits of a commercial fishery, the states of Maryland and Virginia are considering introducing the nonnative Asian oyster ... -
Evaluation of sampling strategies for age determination of cod (Gadus morhua) sampled at the North Sea International Bottom Trawl Survey
Jourdain, Natoya; Breivik, Olav Nikolai; Fuglebakk, Edvin; Aanes, Sondre; Vølstad, Jon Helge (Peer reviewed; Journal article, 2020)The North Sea cod stock assessment is based on indices of abundance-at-age from fishery-independent bottom trawl surveys. The age structure of the catch is estimated by sampling fish for otoliths collection in a length-stratified ... -
Evaluering av datagrunnlaget 2006–2009 for estimering av andel rømt oppdrettslaks i gytebestanden i norske elver : Forslag til forbedringer i utvalgsmetoder og prøvetakingsmetodikk
Skilbrei, Ove; Vølstad, Jon Helge; Bøthun, Gjermund; Svåsand, Terje (Rapport fra Havforskningen;Nr. 7-2011, Working paper, 2011) -
Evaluering av datagrunnlaget 2006–2009 for estimering av andel rømt oppdrettslaks i gytebestanden i norske elver : Forslag til forbedringer i utvalgsmetoder og prøvetakingsmetodikk
Skilbrei, Ove; Vølstad, Jon Helge; Bøthun, Gjermund; Svåsand, Terje (Rapport fra Havforskningen;Nr. 7-2011, Working paper, 2011) -
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, ...