Krill population trends

Krill (Euphausia superba) distribution and abundance data are available from a number of sources: from net surveys (the longest historical series of available date), from acoustic surveys, from fisheries data and from the distribution of krill predators. Each of these forms of data collection has its own biases and limitations and our current understanding of krill distribution and abundance comes from utilising the various forms of data to the maximum extent possible. Time series data are really only available from the South Atlantic where scientific netting programs and annual acoustic surveys have been carried out annually. The South Atlantic is also the area where the fishery has concentrated for the last 20 years. There have been suggestions of changes in the distribution and abundance of Antarctic krill, based mainly on analysis of available scientific net data. There is also evidence of intense inter- and intra-annual variability of krill abundance within regions. These fluctuations in abundance make detection of long-term trends difficult to detect. This review examines the main types of data available for Antarctic krill and will present an indication of the extent and limitations of the available datasets and will present the currently accepted state of knowledge concerning krill distribution, abundance and trends.