A CHARACTERISATION OF THE TOOTHFISH FISHERY IN SUBAREAS 88.1 AND 88.2 FROM 1997/98 TO 2008/09

The exploratory fishery for Dissostichus spp. has now been operating for 13 years in Subarea 88.1 and for 8 years in Subarea 88.2. During that time a large amount of distributional and biological data has been collected on toothfish and the associated bycatch. The purpose of this report is to characterise the general fishing patterns over time and, in particular, to identify possible changes to the fishery which may be indicative of localised stock depletion. We considered here the catch limit, changes in depth/location of fishing, and length and age structure of the population. The catch limit was under caught in both Subareas 88.1 and 88.2 during the 2008 and 2009 seasons. This was mainly due to difficulties in accurately predicting when catches would exceed the catch limit (using the Secretariat’s forecasting routines), but in 2008 was also partly due to the bad ice conditions. The median fishing depth steadily increased over the first seven years of the fishery but has since stabilised at about 1000–1200 m. However, the fishing effort in each of the SSRUs continues to vary due to several factors including the distribution of sea-ice, the SSRU catch and bycatch limits, and an increase in knowledge of the various grounds. Raw catch and effort data examined during this study suggest that the median toothfish catch per set has generally increased over the course of the fishery whilst the median number of hooks per set has remained relatively constant. Other indicators of CPUE including unstandardised catch per hook and catch per set have shown no consistent trend over time. The length frequency data from the Ross Sea fishery have been very consistent over the past 3–4 seasons. There is no evidence of any truncation of the overall length frequency distribution, and no evidence for a reduction in fish length in any SSRU over time. We conclude that from data examined from the fishery to date there is no strong evidence for localised stock depletion.