Browsing Brage IMR by Author "Vølstad, Jon Helge"
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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 ... -
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) -
Fisketuristenes fangster er kartlagt : Recording the catches of fishing tourists
Hauge, Marie; Nilsen, Merete; Vølstad, Jon Helge (Havforskningsnytt;Nr. 7 - 2010, Working paper, 2010)Figures from the Institute of Marine Research show that fishing tourists using the organised tourism industry catch an estimated 3,300 tonnes each year. The estimate is based on advanced statistical methods, practical field ... -
Hummerfisket 2017 og 2018: Innsats og fangst
Kleiven, Alf Ring; Lyle, Jeremy; Ferter, Keno; Espeland, Sigurd Heiberg; Kleiven, Portia Joy Nillos; Christensen, Lene; Vølstad, Jon Helge (Rapport fra havforskningen;2019 - 39, Research report, 2019)I 2017 ble det innført obligatorisk påmelding til hummerfisket for både fritidsfiskere og yrkesfiskere. Dette har lagt grunnlaget for muligheten til å beregne total innsats og fangst av hummer i Norge. Etter hummersesongen ...