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

Research output: Research - peer-reviewJournal article – Annual report year: 2019


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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
StateAccepted/In press - 2019
CitationsWeb of Science® Times Cited: No match on DOI
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ID: 164944643