Close-Kin Mark-Recapture technology in fisheries
Understanding the abundance of wild populations of fish stocks is vital for sustainable management of our Commonwealth-managed species and fisheries.
Close-Kin Mark-Recapture, developed at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), is a technique used to infer population demographics, or the absolute abundance of adults, by identifying close-kin-pairs, for example parent-offspring or half-siblings, among a collection of sampled animals.
The Australian Fisheries Management Authority (AFMA) is working closely with world-leading scientists from the CSIRO to use Close-Kin Mark-Recapture data to determine whether a species is at risk of overfishing. It also assists our fisheries managers in setting ecologically sustainable and profitable harvest strategies.
CSIRO in partnership with AFMA, the commercial fishing industry and other stakeholders, has spearheaded the use of this technology which is revolutionising the way the health and the productivity of fisheries are assessed and managed. Alongside the usual methods of catch and effort and other ‘abundance’ research and information, Close-Kin Mark-Recapture has strengthened the way we manage our species into the future with many other broader applications presenting themselves as genetic technology improves and becomes more cost effective.
Close-Kin Mark-Recapture technology has become a vital component of the successful management of southern bluefin tuna, sharks, and other high-value Commonwealth-managed species.
In 2006, it was revealed that southern bluefin tuna had a concerning level of unreported catches meaning conventional stock assessments were not going to provide scientists with accurate information. Enter close-kin mark-recapture.
“Close-kin mark-recapture is a census, and a very reliable and precise one if sufficient kin pairs are retrieved. The beauty of this method lies in its simplicity. At its core is the genetic and mathematical truth that the greater the proportion of related individuals found in a random sample of a population, the smaller that population must be. In the past, southern bluefin tuna has been overfished. It is now controlled by strict rules and regulations including a shared total allowable catch between many countries. Through this cooperation between fishing countries, the stock has rebounded,” states Peter Grewe, Head Geneticist at CSIRO Oceans and Atmosphere.
Southern bluefin tuna continues to be monitored with world class science using cutting-edge genetic sampling and modelling to support robust decision making in the Commission for the Conservation of Southern Bluefin Tuna. The most recent scientific assessments show continued rebuilding of the stock. In July 2024, southern Bluefin tuna was removed from the listed of threatened species under the Environment Protection and Biodiversity Conservation Act 1999 in part due to the contribution of Close-Kin Mark-Recapture to stock science robust decision making.
AFMA is responsible for managing commercial fishing in Australian waters and for Australian boats on the high seas. We also contribute to discussions at the international level on the scientific processes and decision making of the Commission for the Conservation of Southern Bluefin Tuna. The commercial fishing industry has been a key partner in the sustained recovery of southern bluefin tuna.
AFMA works closely with the Australian Department of Agriculture, Fisheries and Forestry, the Commission for the Conservation of Southern Bluefin Tuna, and the Australian fishing industry to ensure the future of the species.
The Australian southern bluefin tuna fishery is estimated to be worth 33 million dollars, mainly in exports.