Nils Olav Handegard

Nils Olav Handegard

orcid

Research Focus & Metrics

Academic Career Length

24Years (2003-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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22 January 2015 in Fish and Fisheries
Verified
Journal Article
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MSMette Skern‐Mauritzen
Mette Skern‐Mauritzen
GOGeir Ottersen
Geir Ottersen
NHNils Olav Handegard
Nils Olav Handegard
GHGeir Huse
Geir Huse
DIDingsør
Dingsør
OKOlav S Kjesbu
Olav S Kjesbu
Fish stock productivity, and thereby sensitivity to harvesting, depends on physical (e.g. ocean climate) and biological (e.g. prey availability, competition and predation) processes in the ecosystem. The combined impacts of such ecosystem processes and fisheries have lead to stock collapses across the world. While traditional fisheries management focuses on harvest rates and stock biomass, incorporating the impacts of such ecosystem processes are one of the main pillars of the ecosystem approach to fisheries management (EAFM). AlthoughEAFMhas been formally adopted widely since the 1990s, little is currently known to what extent ecosystem drivers of fish stock productivity are actually implemented in fisheries management. Based on worldwide review of more than 1200 marine fish stocks, we found that such ecosystem drivers were implemented in the tactical management of only 24 stocks. Most of these cases were in the North Atlantic and north‐east Pacific, where the scientific support is strong. However, the diversity of ecosystem drivers implemented, and in the approaches taken, suggests that implementation is largely a bottom‐up process driven by a few dedicated experts. Our results demonstrate that tactical fisheries management is still predominantly single‐species oriented taking little account of ecosystem processes, implicitly ignoring that fish stock production is dependent on the physical and biological conditions of the ecosystem. Thus, while the ecosystem approach is highlighted in policy, key aspects of it tend yet not to be implemented in actual fisheries management.

1 July 2012 in Current Biology
Verified
Journal Article
Closed access
NHNils Olav Handegard
Nils Olav Handegard
KBKevin M. Boswell
Kevin M. Boswell
CIChristos C. Ioannou
Christos C. Ioannou
SLSimon P. Leblanc
Simon P. Leblanc
DTDag B. Tjøstheim
Dag B. Tjøstheim
ICIain D. Couzin
Iain D. Couzin

19 October 2012 in ICES Journal of Marine Science
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Journal Article
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ARAlex De Robertis
Alex De Robertis
NHNils Olav Handegard
Nils Olav Handegard
De Robertis, A. and Handegard, N. O. 2013. Fish avoidance of research vessels and the efficacy of noise-reduced vessels: a review. – ICES Journal of Marine Science, 70:34–45. 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 established to minimize fish reactions. We review the literature on fish reactions to vessels appearing since these recommendations were made, focusing on acoustic surveys, and compare how fish react to noise-reduced and conventional vessels. Reactions to approaching vessels are variable and difficult to predict. However, the behaviour can bias acoustic abundance measurements, and should be considered when performing acoustic surveys. The few comparisons of acoustic abundance measurements from noise-reduced and conventional vessels are contradictory, but demonstrate that the sound pressure level, on which the noise-reduction criterion is based, is insufficient to explain how fish react to survey vessels. Further research is needed to identify the stimuli fish perceive from approaching vessels and the factors affecting whether fish perceiving these stimuli will react before further recommendations to reduce vessel-avoidance reactions can be made. In the interim, measurement of the biases introduced by fish avoidance reactions during surveys, and timing of surveys when fish are in a less reactive state, may reduce errors introduced by vessel avoidance.

15 March 2007 in The Journal of the Acoustical Society of America
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Journal Article
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EOEgil Ona
Egil Ona
OGOlav Rune Godø
Olav Rune Godø
NHNils Olav Handegard
Nils Olav Handegard
VHVidar Hjellvik
Vidar Hjellvik
RPRuben Patel
Ruben Patel
GPGeir Pedersen
Geir Pedersen
Behavior of herring (Clupea harengus) is stimulated by two ocean-going research vessels; respectively designed with and without regard to radiated-noise-standards. Both vessels generate a reaction pattern, but, contrary to expectations, the reaction initiated by the silent vessel is stronger and more prolonged than the one initiated by the conventional vessel. The recommendations from the scientific community on noise-reduced designs were motivated by the expectation of minimizing bias on survey results caused by vessel-induced fish behavior. In conclusion, the candidate stimuli for vessel avoidance remain obscure. Noise reduction might be necessary but is insufficient to obtain stealth vessel assets during surveys.

1 July 2003 in Aquatic Living Resources
Verified
Journal Article
Closed access
NHNils Olav Handegard
Nils Olav Handegard

24 May 2012 in Fish and Fisheries
Verified
Journal Article
Closed access
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NHNils Olav Handegard
Nils Olav Handegard
LBLouis du Buisson
Louis du Buisson
Patrice BREHMERPatrice BREHMER
Patrice BREHMER
SCStewart J Chalmers
Stewart J Chalmers
ARAlex De Robertis
Alex De Robertis
OGOlav Rune Godø
Olav Rune Godø