A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland
Stocks of Pandalus borealis off West Greenland have been assessed using a research trawl survey since 1988. The survey has used a design of randomly placed stations, stratified ton depth data where available, using small blocks elsewhere), with sampling effort proportional to stratum area. In some y...
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ftdtupubl:oai:pure.atira.dk:publications/dd732076-9c89-4c9e-8ebb-be185c3379d8 2024-04-28T08:21:29+00:00 A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland Folmer, Ole Pennington, M. 2000 https://orbit.dtu.dk/en/publications/dd732076-9c89-4c9e-8ebb-be185c3379d8 eng eng https://orbit.dtu.dk/en/publications/dd732076-9c89-4c9e-8ebb-be185c3379d8 info:eu-repo/semantics/restrictedAccess Folmer , O & Pennington , M 2000 , ' A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland ' , Fisheries Research , vol. 49 , no. 2 , pp. 165-178 . Bestandsvurdering article 2000 ftdtupubl 2024-04-03T14:47:44Z Stocks of Pandalus borealis off West Greenland have been assessed using a research trawl survey since 1988. The survey has used a design of randomly placed stations, stratified ton depth data where available, using small blocks elsewhere), with sampling effort proportional to stratum area. In some years, a two-stage adaptive sampling scheme was used to place more stations into strata with large first-stage variation in catches. The design of the survey was reviewed in 1998. Modifications in survey design suggested were to shorten tow duration, to pool strata so that effort could be allocated more efficiently, to put a higher proportion of stations in high- density areas and to abandon two-stage sampling. All these changes were implemented for the 1998 survey, except that tow duration was reduced to 30 min at 25% of the stations. To analyze the-efficiency of the present survey design, various statistical techniques were used to estimate two indices of shrimp abundance and their precision, and to determine the effective sample sizes for estimates of length-frequency distributions. It is concluded that the surveys produce a fairly precise abundance index, and that given the relatively small effective sample size, reducing tow duration to 15 min would increase overall survey precision. An unexpected outcome of the analysis is that the density of shrimp appears to have been fairly stable over the last 11 years. (C) 2000 Elsevier Science B.V. All rights reserved. Article in Journal/Newspaper Greenland Pandalus borealis Technical University of Denmark: DTU Orbit |
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Technical University of Denmark: DTU Orbit |
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ftdtupubl |
language |
English |
topic |
Bestandsvurdering |
spellingShingle |
Bestandsvurdering Folmer, Ole Pennington, M. A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland |
topic_facet |
Bestandsvurdering |
description |
Stocks of Pandalus borealis off West Greenland have been assessed using a research trawl survey since 1988. The survey has used a design of randomly placed stations, stratified ton depth data where available, using small blocks elsewhere), with sampling effort proportional to stratum area. In some years, a two-stage adaptive sampling scheme was used to place more stations into strata with large first-stage variation in catches. The design of the survey was reviewed in 1998. Modifications in survey design suggested were to shorten tow duration, to pool strata so that effort could be allocated more efficiently, to put a higher proportion of stations in high- density areas and to abandon two-stage sampling. All these changes were implemented for the 1998 survey, except that tow duration was reduced to 30 min at 25% of the stations. To analyze the-efficiency of the present survey design, various statistical techniques were used to estimate two indices of shrimp abundance and their precision, and to determine the effective sample sizes for estimates of length-frequency distributions. It is concluded that the surveys produce a fairly precise abundance index, and that given the relatively small effective sample size, reducing tow duration to 15 min would increase overall survey precision. An unexpected outcome of the analysis is that the density of shrimp appears to have been fairly stable over the last 11 years. (C) 2000 Elsevier Science B.V. All rights reserved. |
format |
Article in Journal/Newspaper |
author |
Folmer, Ole Pennington, M. |
author_facet |
Folmer, Ole Pennington, M. |
author_sort |
Folmer, Ole |
title |
A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland |
title_short |
A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland |
title_full |
A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland |
title_fullStr |
A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland |
title_full_unstemmed |
A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland |
title_sort |
statistical evaluation of the design and precision of the shrimp trawl survey off west greenland |
publishDate |
2000 |
url |
https://orbit.dtu.dk/en/publications/dd732076-9c89-4c9e-8ebb-be185c3379d8 |
genre |
Greenland Pandalus borealis |
genre_facet |
Greenland Pandalus borealis |
op_source |
Folmer , O & Pennington , M 2000 , ' A statistical evaluation of the design and precision of the shrimp trawl survey off West Greenland ' , Fisheries Research , vol. 49 , no. 2 , pp. 165-178 . |
op_relation |
https://orbit.dtu.dk/en/publications/dd732076-9c89-4c9e-8ebb-be185c3379d8 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1797583798449209344 |