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An assessment of Icelandic flatfish stocks Valtysson, Hreidar Tor
Abstract
Multispecies, multispatial assessment is provided for megrim, witch flounder, American plaice, dab, lemon sole, and plaice in Icelandic waters. Information used as input are logbook records on individual sets from the Danish seine fleet, biological samples mostly from port of landing, and information on individual tows from annual trawl surveys since 1985. Results are compared to commercial CPUE from the English trawler fleet that used to operate in Icelandic waters. Where data allowed the stocks were analysed with a delay difference model, cohort analysis, yield per recruit, and catch curve analysis. These models treated each species as a single stock. The condition of the flatfish stocks vary. All models indicate that the megrim stock is declining to a very low level. Megrim is however historically the smallest of the flatfish stocks and is almost exclusively caught as bycatch. Because of this, ways to protect the stock are few. The current catches of the witch flounder are close to estimated maximum sustainable yield. Some signs however indicate that the stock might be overexploited. The American plaice and dab stocks seem to be in good condition and trawl surveys do not show any decline with time. Uncertainties are large for these species and their real size can therefore not be evaluated. Using the same logic, no specific total allowed catch could be recommended. The lemon sole stock seems to be declining in most areas, how much and from what level is however difficult to judge since the models contradict each other. Information used here for the lemon sole might not be sufficient for stock evaluation. No specific TAC could therefore be advised, but on precautionary grounds, since some models estimate the stock to be on a very low level, all direct target fisheries should be limited. The plaice stock has been declining on most of the major grounds for about a decade. The stock is now at a very low level and all fishery should be reduced considerably.
Item Metadata
Title |
An assessment of Icelandic flatfish stocks
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1999
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Description |
Multispecies, multispatial assessment is provided for megrim, witch flounder, American plaice,
dab, lemon sole, and plaice in Icelandic waters. Information used as input are logbook records on
individual sets from the Danish seine fleet, biological samples mostly from port of landing, and
information on individual tows from annual trawl surveys since 1985. Results are compared to
commercial CPUE from the English trawler fleet that used to operate in Icelandic waters. Where data
allowed the stocks were analysed with a delay difference model, cohort analysis, yield per recruit, and
catch curve analysis. These models treated each species as a single stock. The condition of the flatfish
stocks vary. All models indicate that the megrim stock is declining to a very low level. Megrim is
however historically the smallest of the flatfish stocks and is almost exclusively caught as bycatch.
Because of this, ways to protect the stock are few. The current catches of the witch flounder are close to
estimated maximum sustainable yield. Some signs however indicate that the stock might be
overexploited. The American plaice and dab stocks seem to be in good condition and trawl surveys do
not show any decline with time. Uncertainties are large for these species and their real size can therefore
not be evaluated. Using the same logic, no specific total allowed catch could be recommended. The
lemon sole stock seems to be declining in most areas, how much and from what level is however difficult
to judge since the models contradict each other. Information used here for the lemon sole might not be
sufficient for stock evaluation. No specific TAC could therefore be advised, but on precautionary
grounds, since some models estimate the stock to be on a very low level, all direct target fisheries should
be limited. The plaice stock has been declining on most of the major grounds for about a decade. The
stock is now at a very low level and all fishery should be reduced considerably.
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Extent |
12770296 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-06-11
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0074820
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1999-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.