The Patagonian toothfish (Dissostichus eleginoides) has been fished in the Kerguelen Islands zone for 20 years, firstly with trawlers and more recently with longliners. It is the oldest fishery of the Indian sector of the Southern Ocean. However IUU fishing has appeared in 1997. A GLM analysis has been performed from the statistical data of the legal fishery to assess the factors affecting the catch per unit effort (CPUE) both from the trawl and the longline fishery. The recent trends show a decrease of the CPUE, indicating a probable local overfishing. The bathymetric spreading of the fishery seems to have partially occulted this situation. In addition some biological facts (such as depth distribution, spawning date and place, and movements between geographical sectors), of the adult part of the population have been obtained from a scientific programme conducted by the fishery observers onboard the fishing vessels.