Patagonian toothfish (Dissostichus eleginoides) have been fished in the Kerguelen Islands zone for 20 years, firstly with trawlers and more recently with longliners. This is the oldest fishery targeting D. eleginoides in the Indian Ocean sector of the Southern Ocean. However illegal, unreported and unregulated (IUU) fishing has occurred in the area since 1997. A generalised linear model (GLM) analysis was performed using statistical data from the legal fishery to assess the trends in and the factors affecting catch-per-unit-effort (CPUE) in both the trawl and the longline fisheries. The most recent trends show a decrease in CPUE, indicating probable local overfishing. The expansion of the bathymetric range of the fishery to increasingly deeper waters seems to have partially masked this situation. In addition, some biological data (such as depth distribution, timing and area of spawning, and movements between geographical sectors) on the adult section of the exploited population have been obtained from scientific observation programs conducted by fishery observers on board fishing vessels.