De Robertis et al, 2017 - Chukchi shelf acoustic-trawl survey (corrected)
Description
Abundance estimates of fishes from Acoustic-trawl surveys of the US sector of the Chukchi Sea continental shelf conducted in 2012 and 2013. These surveys are described in De Robertis, A., Taylor, K., Wilson, C., and Farley, E. 2017a. Abundance and Distribution of Arctic cod (Boreogadus saida) and other Pelagic Fishes over the U.S. Continental Shelf of the Northern Bering and Chukchi Seas Deep-Sea Research II, 135: 51-65. http://dx.doi.org/10.1016/j.dsr2.2016.03.002 Please note that an error was detected after publication related to the adjustments for selectivity (i.e. probability of retention in the trawl). De Robertis et al. 2017a applied calculations used selectivity relationships from De Robertis, A., Taylor, K., Williams, K., and Wilson, C. D. 2017b. Species and size selectivity of two midwater trawls used in an acoustic survey of the Alaska Arctic. Deep Sea Research II, 135: 40-50. http://dx.doi.org/10.1016/j.dsr2.2015.11.014 An error was discovered in a parameter these selectivity calculations, and a correction publication is being prepared. Specifically, in De Robertis et al, 2017b, the proportion of meshes covered by recapture nets in this experiment was estimated as 0.022 in the forward portion of the trawl, and 0.055 was used in the aft portion of the trawl. Since publication of this work, we have discovered that these values were incorrectly computed. The correct value of fmar in the experimental configuration is 0.065 in the forward portion of the trawl, and 0.132 in the aft portion of the trawl. This error is described and corrected in the following publication De Robertis, A., Taylor, K., Wilson, C., and Williams, K. In press. Corrigendum - Species and size selectivity of two midwater trawls used in an acoustic survey of the Alaska Arctic. Deep Sea Research II. These files contain abundance data from De Robertis et al., 2017a reprocessed to use the corrected selectivity values given in table 1 of De Robertis et al., in press. The impact on abundance estimates is relatively modest: total estimates for Arctic cod are within 0.7% of the previous estimates and those of other, less abundant, species at most 9.9 %. In addition size distributions shifted towards larger sizes: mean size increased by up to 1.1% for Arctic and saffron cod, and by up to 7.8 % for capelin and herring Overall, the differences are smaller than the changes on selectivity relationships as the relative change in retention of different species and size classes was much smaller than the absolute changes. Thus, the impact of the error described above on the abundance estimates reported by De Robertis et al. (2017b) is relatively small, and does not appreciably alter the conclusions of the study. These revised data should be used in future studies. We have also provided estimates of walleye pollock abundance that were not included in the original publication - these were computed with the methods described in De Robertis et al., 2017a,.
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Steps to reproduce
Please see De Robertis, A., Taylor, K., Wilson, C., and Farley, E. 2017. Abundance and Distribution of Arctic cod (Boreogadus saida) and other Pelagic Fishes over the U.S. Continental Shelf of the Northern Bering and Chukchi Seas Deep-Sea Research II, 135: 51-65. http://dx.doi.org/10.1016/j.dsr2.2016.03.002 for abundance calculations and De Robertis, A., Taylor, K., Wilson, C., and Williams, K. In review. Corrigendum - Species and size selectivity of two midwater trawls used in an acoustic survey of the Alaska Arctic. Deep Sea Research II. for the corrected selectivity values used to estimate these abundances.