An Australian zoologist now at the University of Melbourne, along with colleagues from the United Kingdom and New Zealand, was the first to record a decline in the genetic diversity of a commercially exploited marine species. Their findings, published in the latest volume of the Proceedings of the National Academy of Sciences, shout a warning that could force a rethink to current fisheries management and the research focus into sustainable fishing.
Dr Greg Adcock analysed the DNA found in scales preserved from two populations of New Zealand snapper collected from the 1950s to 1998. One population had been commercially fished since the late 1800s. The other was a 'virgin' population, being subjected to subsistence and recreational fishing only until the scale collection began.
Adcock and colleagues found that the 'virgin' population from Tasman Bay on New Zealand's South Island had suffered an unexpected decline in genetic diversity, starting from the time it began to be commercially exploited in the 1950s.
The other population, from the North Island's Hauraki Bay, showed no decline in genetic diversity in the nearly 50 years to 1998.
The paper reports that the Tasman Bay's effective population size (the number of fish in the population capable of breeding) is100,000 times fewer than its total number, and several orders of magnitude lower than expected.
"In Tasman Bay, commercial fishing has often reduced total numbers to as low as about one million. This leaves only a few hundred fish to contribute to the next generation, a dangerously low genetic base from which to sustain a population," says Adcock.
"With a high effective population you can retain a large amount of rare genetic variation. Such variation is lost as numbers
Contact: Jason Major
University of Melbourne