Intercalibration of survey methods using paired fishing operations and log-Gaussian Cox processes

Uffe Høgsbro Thygesen*, Kasper Kristensen, Teunis Jansen, Jan E Beyer

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

We present a statistical method for intercalibration of fishery surveys methods, i.e. determining the difference in catchability and size selectivity of two methods, such as trawl gears or vessels, based on data from paired fishing operations. The model estimates the selectivity ratios in each length class by modelling the size distribution of the underlying population at each station and the size-structured clustering of fish at small temporal and spatial scales. The model allows for overdispersion and correlation between catch counts in neighbouring size classes. This is obtained by assuming Poisson-distributed catch numbers conditional on unobserved log-Gaussian variables, i.e. the catch is modelled using log-Gaussian Cox processes. We apply the method to catches of hake (Merluccius paradoxus and M. capensis) in 341 paired trawl hauls performed by two different vessels, viz. the RV Dr Fridtjof Nansen and the FV Blue Sea, operating off the coast of Namibia. The results demonstrate that it is feasible to estimate the selectivity ratio in each size class, and to test statistically the hypothesis that the selectivity is independent of size or species. For the specific case, we find that differences between size classes and species are statistically significant.
Original languageEnglish
JournalICES Journal of Marine Science
Volume76
Issue number4
Pages (from-to)1189-1199
ISSN1054-3139
DOIs
Publication statusPublished - 2019

Keywords

  • Intercalibration
  • Log-Gaussian Cox processes
  • Mixed-effects models
  • Selectivity

Cite this

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title = "Intercalibration of survey methods using paired fishing operations and log-Gaussian Cox processes",
abstract = "We present a statistical method for intercalibration of fishery surveys methods, i.e. determining the difference in catchability and size selectivity of two methods, such as trawl gears or vessels, based on data from paired fishing operations. The model estimates the selectivity ratios in each length class by modelling the size distribution of the underlying population at each station and the size-structured clustering of fish at small temporal and spatial scales. The model allows for overdispersion and correlation between catch counts in neighbouring size classes. This is obtained by assuming Poisson-distributed catch numbers conditional on unobserved log-Gaussian variables, i.e. the catch is modelled using log-Gaussian Cox processes. We apply the method to catches of hake (Merluccius paradoxus and M. capensis) in 341 paired trawl hauls performed by two different vessels, viz. the RV Dr Fridtjof Nansen and the FV Blue Sea, operating off the coast of Namibia. The results demonstrate that it is feasible to estimate the selectivity ratio in each size class, and to test statistically the hypothesis that the selectivity is independent of size or species. For the specific case, we find that differences between size classes and species are statistically significant.",
keywords = "Intercalibration, Log-Gaussian Cox processes, Mixed-effects models, Selectivity",
author = "Thygesen, {Uffe H{\o}gsbro} and Kasper Kristensen and Teunis Jansen and Beyer, {Jan E}",
year = "2019",
doi = "10.1093/icesjms/fsy191",
language = "English",
volume = "76",
pages = "1189--1199",
journal = "I C E S Journal of Marine Science",
issn = "1054-3139",
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Intercalibration of survey methods using paired fishing operations and log-Gaussian Cox processes. / Thygesen, Uffe Høgsbro; Kristensen, Kasper; Jansen, Teunis; Beyer, Jan E.

In: ICES Journal of Marine Science, Vol. 76, No. 4, 2019, p. 1189-1199.

Research output: Contribution to journalJournal articleResearchpeer-review

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T1 - Intercalibration of survey methods using paired fishing operations and log-Gaussian Cox processes

AU - Thygesen, Uffe Høgsbro

AU - Kristensen, Kasper

AU - Jansen, Teunis

AU - Beyer, Jan E

PY - 2019

Y1 - 2019

N2 - We present a statistical method for intercalibration of fishery surveys methods, i.e. determining the difference in catchability and size selectivity of two methods, such as trawl gears or vessels, based on data from paired fishing operations. The model estimates the selectivity ratios in each length class by modelling the size distribution of the underlying population at each station and the size-structured clustering of fish at small temporal and spatial scales. The model allows for overdispersion and correlation between catch counts in neighbouring size classes. This is obtained by assuming Poisson-distributed catch numbers conditional on unobserved log-Gaussian variables, i.e. the catch is modelled using log-Gaussian Cox processes. We apply the method to catches of hake (Merluccius paradoxus and M. capensis) in 341 paired trawl hauls performed by two different vessels, viz. the RV Dr Fridtjof Nansen and the FV Blue Sea, operating off the coast of Namibia. The results demonstrate that it is feasible to estimate the selectivity ratio in each size class, and to test statistically the hypothesis that the selectivity is independent of size or species. For the specific case, we find that differences between size classes and species are statistically significant.

AB - We present a statistical method for intercalibration of fishery surveys methods, i.e. determining the difference in catchability and size selectivity of two methods, such as trawl gears or vessels, based on data from paired fishing operations. The model estimates the selectivity ratios in each length class by modelling the size distribution of the underlying population at each station and the size-structured clustering of fish at small temporal and spatial scales. The model allows for overdispersion and correlation between catch counts in neighbouring size classes. This is obtained by assuming Poisson-distributed catch numbers conditional on unobserved log-Gaussian variables, i.e. the catch is modelled using log-Gaussian Cox processes. We apply the method to catches of hake (Merluccius paradoxus and M. capensis) in 341 paired trawl hauls performed by two different vessels, viz. the RV Dr Fridtjof Nansen and the FV Blue Sea, operating off the coast of Namibia. The results demonstrate that it is feasible to estimate the selectivity ratio in each size class, and to test statistically the hypothesis that the selectivity is independent of size or species. For the specific case, we find that differences between size classes and species are statistically significant.

KW - Intercalibration

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KW - Mixed-effects models

KW - Selectivity

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