THE SELECTION OF TRIPS BASED ON DATA METRICS FOR THE ASSESSMENT OF ANTARCTIC TOOTHFISH IN THE ROSS SEA

A dataset for the 2009 assessment of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea Region was selected on the basis of data quality metrics for individual trips. Initial informative datasets were selected comprising trips with high (above median) rates of recovery of previously released tags, and/or where tags released on the trip were subsequently recaptured at a high rate. These trips were used to define a range for various data quality metrics considered to be informative with respect to tagging data. Other trips with data quality metric values within these ranges were added to the dataset. Where the initial informative dataset was selected comprising trips with above median rate of tag recovery or where released tags were recaptured at a high rate, the majority of the catches, tag releases and tag recoveries are retained: the resulting dataset is only slightly smaller than the full dataset. However, where trips included in the informative dataset must have both an above median rate of tag recoveries and where tags released on the trip must be captured at an above median rate, the resulting dataset is smaller, but nevertheless substantially larger than that provided by New Zealand vessels alone. The methods used here provide a means of objectively selecting trips considered to have suitable tagging data quality for use in an assessment.