GENETAG: Genetic mark-recapture for real-time harvest rate monitoring
Pilot studies in northern Australian Spanish mackerel (Scomberomorus commerson) fisheries
Jenny Ovenden, Damien Broderick and Michael Macbeth
Supported by funding from the Fisheries Research and Development Corporation (FRDC) on behalf of the Australian Government ( 2002/011)
Genetagging is the mark-recapture estimation of two essential fisheries assessment statistics; the fishery harvest rate (U) and catchability (q), over time. Fish are ‘marked’ following remote, in situ tissue sampling and subsequent DNA genotyping. Remote tissue samples are collected using the ‘genetag’ lures. Fish are not captured and landed for tagging in the conventional manner, which avoids some of the serious limitations of conventional tagging such as mortality and behavioural changes associated with the tagging and release process. Furthermore, tags are not lost. Under-reporting, which leads to a dangerous optimistic bias in estimated fishery harvest rate (U), is avoided, as a known proportion of the commercial catch is screened.
The genetic tagging approach would be useful in any fishery where more usual monitoring methods, such as survey, age structure analyses and conventional tagging, are problematic, and especially where the value of individual fish is sufficiently high, to justify the significant costs of genetagging.
We have developed a new monitoring method (“genetagging”) that may be applied to a wide variety of fisheries. In this report, we report the development and evaluation of protocols specifically for the Spanish mackerel (Scomberomorus commerson) fishery of the Northern Territory.