Effect of fisher’s soak tactic on catch pattern in the Danish gillnet plaice fishery

Abstract

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Introducingselfisher: open source software for statistical analyses of fishing gear selectivity

“…A graphical comparison to the published results in Savina et al (2017; in red) shows that the estimated catch comparison curves and relative CIs are very similar.…”

“…, aes(width, prop))+geom_point(aes(size=total))+ geom_line(data = newdata)+ geom_ribbon(data = newdata, aes(ymin = lo, ymax = hi), alpha = 0.2)+ ylab("Catch comparison rate") to the published results inSavina et al (2017; in red) shows that the estimated catch comparison curves and relative CIs are very similar. , aes(width, prop/(1-prop))) + geom_point(aes(size = total))+ geom_line(data = newdata)+ geom_ribbon(data = newdata, aes(ymin = CRlo, ymax = CRhi), alpha = 0…”

“…Additional information relative to fishing conditions and catch characteristics were recorded at haul level. This example deals with data from an experiment originally published by Savina et al (2017). Two soak tactics, i.e., 12h at day and 12h at night, were compared in the Danish gillnet plaice fishery to estimate whether a change in soak tactics could help to catch less of the unwanted bycatch, i.e., the invertebrate edible crab (Cancer pagurus).…”

“…We describe three general categories of statistical models, divided based on the mathematical probabilities underlying the estimation, while omitting details about experimental designs and code to run the models. Then, we describe the bootstrapping procedure used to account for variation within and between hauls in selectivity (Millar, 1993), potentially resampling from distinct pools of hauls based on gear type or tactic as in unpaired hauls (Herrmann et al, 2017; Savina et al, 2017). Then, we briefly describe four case studies used to illustrate the package’s capabilities, while providing more thorough descriptions with R code in online appendices.…”

“…Then, we briefly describe four case studies used to illustrate the package’s capabilities, while providing more thorough descriptions with R code in online appendices. The case studies are (1) a covered codend study of haddock ( Melanogrammus aeglefinus ) with four different codends (O’Neill et al, 2016), (2) a paired gear study in a brown shrimp ( Crangon crangon ) trawl fishery where one trawl is nonselective (Santos et al, 2018), (3) a catch comparison study of unpaired hauls of gillnets avoiding an unwanted crab ( Cancer pagurus ) (Savina et al, 2017), and (4) a catch comparison study of paired hauls in a Norway lobster ( Nephrops norvegicus ) trawl fishery (Melli et al, 2018). Finally, we discuss current limitations of the package and potential future advancements.…”