How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach

The Norwegian spring spawning herring is assessed each year from acoustic surveys. The age structure in the stock is estimated from trawl samples. Typically, about 10 trawl samples are taken per survey, and 100 fish from each sample are age measured. The uncertainty in the age structure estimate dep...

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Bibliographic Details
Main Authors: Hjellvik, Vidar, Ona, Egil
Format: Report
Language:English
Published: ICES 2006
Subjects:
Online Access:http://hdl.handle.net/11250/100905
id ftimr:oai:imr.brage.unit.no:11250/100905
record_format openpolar
spelling ftimr:oai:imr.brage.unit.no:11250/100905 2024-09-15T18:40:25+00:00 How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach Hjellvik, Vidar Ona, Egil 2006 400333 bytes application/pdf http://hdl.handle.net/11250/100905 eng eng ICES ICES CM documents 2006/I:24 http://hdl.handle.net/11250/100905 13 s. herring sild acoustics akustikk VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924 VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Resource biology: 921 Working paper 2006 ftimr 2024-07-31T03:37:25Z The Norwegian spring spawning herring is assessed each year from acoustic surveys. The age structure in the stock is estimated from trawl samples. Typically, about 10 trawl samples are taken per survey, and 100 fish from each sample are age measured. The uncertainty in the age structure estimate depends both on the number of trawl hauls and the number of fish for which the age is measured within each haul. The same is true for the length structure. Length is much easier to measure than age, and in the Vestfjorden survey in December 2002, more than 6000 fish distributed on 72 trawl samples were length measured, making possible the investigation undertaken in this paper, where the bootstrap is applied to estimate the number of hauls/fish needed to obtain a given precision in the length distribution. It is reasonable to believe that the precision in the age distribution will depend on the number of fish/hauls in the same way. The sampling intensity needed to obtain a given CV for the most abundant length groups was much lower than for the less abundant length groups. In terms of standard errors it was the other way round. A doubling of number of fish measured per haul from 1 to 2 allowed for about 50% decrease in the number of hauls needed to keep the same precision. A doubling from 128 to 256 allowed for about 10% decrease. Report Vestfjorden Institute for Marine Research: Brage IMR
institution Open Polar
collection Institute for Marine Research: Brage IMR
op_collection_id ftimr
language English
topic herring
sild
acoustics
akustikk
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Resource biology: 921
spellingShingle herring
sild
acoustics
akustikk
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Resource biology: 921
Hjellvik, Vidar
Ona, Egil
How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach
topic_facet herring
sild
acoustics
akustikk
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Resource biology: 921
description The Norwegian spring spawning herring is assessed each year from acoustic surveys. The age structure in the stock is estimated from trawl samples. Typically, about 10 trawl samples are taken per survey, and 100 fish from each sample are age measured. The uncertainty in the age structure estimate depends both on the number of trawl hauls and the number of fish for which the age is measured within each haul. The same is true for the length structure. Length is much easier to measure than age, and in the Vestfjorden survey in December 2002, more than 6000 fish distributed on 72 trawl samples were length measured, making possible the investigation undertaken in this paper, where the bootstrap is applied to estimate the number of hauls/fish needed to obtain a given precision in the length distribution. It is reasonable to believe that the precision in the age distribution will depend on the number of fish/hauls in the same way. The sampling intensity needed to obtain a given CV for the most abundant length groups was much lower than for the less abundant length groups. In terms of standard errors it was the other way round. A doubling of number of fish measured per haul from 1 to 2 allowed for about 50% decrease in the number of hauls needed to keep the same precision. A doubling from 128 to 256 allowed for about 10% decrease.
format Report
author Hjellvik, Vidar
Ona, Egil
author_facet Hjellvik, Vidar
Ona, Egil
author_sort Hjellvik, Vidar
title How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach
title_short How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach
title_full How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach
title_fullStr How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach
title_full_unstemmed How many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for Norwegian spring spawning herring? A bootstrap approach
title_sort how many trawl hauls, and how many fish from each haul are needed to obtain a given precision in the age structure estimate for norwegian spring spawning herring? a bootstrap approach
publisher ICES
publishDate 2006
url http://hdl.handle.net/11250/100905
genre Vestfjorden
genre_facet Vestfjorden
op_source 13 s.
op_relation ICES CM documents
2006/I:24
http://hdl.handle.net/11250/100905
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