Trawl survey of the Patagonian toothfish (Dissostichus eleginoides) resource off the Prince Edward Islands

A bottom trawl survey was conducted in the northern half of the South African EEZ around the Prince Edward Islands in April 2001. Due to the paucity of bathymetric data, it was not possible to design a statistically rigid survey, consequently this first survey is regarded as a pilot study to ascertain the feasibility of conducting future trawl surveys, and to collect relevant data to aid in the design of such surveys should they be deemed practical.
The maximum operating depth for the survey vessel was 1 500metres. Over 90% of the survey area is deeper than 1 500m and, therefore, cannot be surveyed by bottom trawl. The small area above the 1 500m isobath is scattered over 28 hills and seamounts (of various sizes and heights). This combination of factors makes the design and execution of bottom trawl surveys extremely difficult.
A total of 55 trawls were completed and these show a relationship between Patagonian toothfish density and latitude and/or depth. Although this pilot survey was not designed to yield a biomass estimate, a first, crude for Patagonian toothfish estimate is presented. 51 Patagonian toothfish were tagged and released.