This report summarises the timing, depth, and location of fishing effort together with biological characteristics of the catch of Antarctic toothfish up to and including the 2015 season. In 2015, the Ross Sea slope SSRUs were significantly constrained by sea ice and catches were unevenly distributed across the three SSRUs (73% in 88.1H, 22% in 88.1K and 5% in 88.1I). As in recent years, the remaining catches came mainly from SSRUs 88.1C, 88.1J, and 88.2L. A standardised CPUE analysis showed changes in CPUE that were not consistent with biologically driven changes in abundance and are considered not to be indexing abundance.
Length frequency distributions of Antarctic toothfish in the Ross Sea fishery were stable in the North up until 2014, then showed a decrease in mode, particularly for males (to less than 150 cm TL). Distributions in the Shelf have become unimodal and less variable in the last three years. The strong mode of smaller (90–120 cm TL) toothfish present in the Slope fishery from 2010–2013 was not present in the 2014 and 2015 seasons, and the size composition in 2014 and 2015 was similar to that in the early period of the fishery – the reason for this is unclear. There has been a slight reduction in mean age in SSRU 88.2H, but the data are very uncertain due to the paucity of otolith readings and it is recommended that additional otolith readings for this area are given a high priority. There has been a marked increase in the proportion of males in the Ross Sea North fishery throughout the series but little change in sex ratio in the other areas.