This paper reports the preliminary results of by-catch analysis as a part of progress report for the research fishery of Dissostichus spp. in Subarea 48.6 by Japan and South Africa during 2012/13–2016/17. We have used data set provided by CCAMLR secretariat on 10th May, 2017.
Although the by-catch occurred in most longline research operations, the number of by-catch individuals was less than 100 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. ICX is also common by-catch species, but mainly fished at the ice ridge research blocks 48.6_4 and 48.6_5.
The results of the GLM and its model selection with AIC criteria indicates that the number of by-catch GRV individuals is higher at southern research blocks (48.6_3, 48.6_4, and 48.6_5). On the other hands, the number of ANT by-catch individuals is highest at research blocks 48.6_1. As temporal change of by-catch, only GRV shows obvious decrease in number of by-catch individuals.