Those who live, or holiday, in the ‘Mahurangi Matters catchment’ are blessed with great beaches, coastline, swimming, boating and fishing. For avid fishers, there is nothing better than to be out on the water with the prospect of taking home a snapper for dinner.
These are an iconic gulf species and the most common target for recreational fishers. Like all targeted species, they are a ‘commons resource’ that we collectively share. And, like all such shared resources, things work fine until harvesting pressure reaches a point where individual competition ramps up, resulting in resource depletion and collapse – something called ‘the tragedy of the commons’. How can we individually and collectively work to avoid that potential future for our fishing stocks?
Sustainable levels of fish stocks obviously depend on managing catch rates, but also depend on new young fish coming into the fishery. Robust cohorts of new recruits to a local fishing area depend on a range of factors, including larval supply, suitable settlement habitat, and a healthy productive environment that encourage the growing fish to remain in the ‘hood’. Good news from recently published research shows that for the area from Cape Rodney to the Mahurangi Harbour, more than 10 per cent of the new settled snapper juveniles come from adult snapper resident in the Goat Island marine reserve. So, a reserve covering about one per cent of the area is providing 10 per cent of the new recruits!
Suitable settlement habitat for juvenile snapper is also a positive feature of this area. Both Kawau Bay, with its extensive sea-grass beds, and Mahurangi Harbour have been important nursery grounds for snapper. These assets, though, cannot be taken for granted. Extensive scallop dredging in Kawau Bay has reduced the range and quality of juvenile habitat. This is plainly seen in the increased density of juvenile snapper found in cable zones where dredging is excluded. Mahurangi Harbour, too, has been subject to detrimental sediment loading.
So what can we individually, and collectively, do to sustain our snapper? Clearly we can’t take undersized fish; more than our daily bag limit; or fish in marine reserves. But for the future health of our fisheries we should:
• Not fish too close to marine reserve boundaries
• Limit catch-and-release of undersized fish (use bigger hooks and/or move to
better locations)
• If fishing in water less than 20m deep, release the largest fish as these are the
best breeders, and limit catch-and-release of legal sized fish (as those caught in
deeper water suffer from pressure damage as they are brought to the surface
and may not survive after release), and
• Don’t treat the daily bag limit as a target.
Collectively, we also need to be vigilant and proactive on the quality and extent of juvenile habitat. After all, this is where the next generation of fish reside for the next generation of your family to appreciate. Maximising individual benefits risks the ‘tragedy of the commons’. Taking individual responsibility and supporting collective action will hopefully sustain the ‘blessing of the commons’ that we currently enjoy.
By Professor John Montgomery
Institute of Marine Science and School of Biological Sciences
University of Auckland
