This paper reports the preliminary results of by-catch analysis as a part of progress report for the research fishery of Dissostichus spp. in Division 58.4.3a and 58.4.4b by Japan and France during 2012/13–2016/17. We have used extracted data provided by CCAMLR secretariat on 2nd June, 2017.
Although the by-catch occurred in most longline research operations, the number of by-catch individuals was less than 50 individuals in most of the operations. In most of longline operation, by-catch weight was less than 100 kg and less than 20 % of total catch. GRV and ANT are common by-catch species, which are caught at every research block and every year. RFA is also common by-catch species, but mainly fished at the research block 58.4.3a.
The results of the GLM and its model selection with AIC criteria indicates that the number of by-catch individuals is highest at the research block 58.4.4b_1 for GRV and ANT. As temporal change of by-catch, common three by-catch species represents obvious decrease in number of by-catch individuals. The results of GLMs also imply the influence of fishing method and gears on the by-catch pattern.