Last updateTue, 18 Apr 2017 8am

Why managing fisheries for sustainability is necessary but not sufficient


New Zealand boasts one of the best fisheries management models in the world. But leading edge as it may be, our Quota Management System (QMS) is more about exploiting fisheries resources, albeit sustainably,  than it is about protecting natural biodiversity.

The approach is equivalent to saying ‘let’s farm every inch of our land surface, and not bother about allowing any of it to remain wild and unexploited’. We wouldn’t tolerate this on land, yet no-take areas in the sea have no place as of right under the QMS.

Fortunately we do have some no-take zonesbut they are widely scattered and most are small. Yet these are crucial pockets of the ocean where life can flourish and maintain or regain its natural state. So, as well as well-managed fisheries, we need more of these areas of protection: 

• for the sake of protection of biodiversity
• to ensure that we have research areas that will inform fisheries management
• to ensure that New Zealand's reputation for natural beauty endures

Getting the balance right
Fisheries management is all about productivity of the fishery from an economic standpoint. The goal is about maximising yield (read ‘money’), and not about maintaining a healthy, natural, balanced marine ecosystem with species of all ages and sizes present. There is a complex tale associated with New Zealand's QMS. That tale is about virgin biomass (original unfished stock) and maximum sustainable yield (MSY). The QMS involves the direct control of harvest levels for individual species or stocks of species. Because the QMS can only at anything but broad spatial scales, there is the constant reality of localised depletion, as illustrated below.

Maintaining a healthy fishery is not the same thing as maintaining a healthy ocean.
Fisheries management in New Zealand requires that we do not fish stocks down below a size that supports their MSY. In theory, the MSY is the largest amount of fish you can take OUT of the ocean while still leaving sufficient behind to ensure enough fish to produce new generations to maintain the fishery. This is approximately 23% of the original unfished stock for such fin fish as snapper.

The problem is in the perception.
The key word here is "productivity": the biomass is maintained at a very carefully balanced level to ensure maximum productivity which means, for most fisheries, a very large number of young fish that have just finished their growth-spurt into adulthood. Maximum productivity does NOT mean a balanced spectrum of large, slow-growing grand-dames and sires (the ones some of the rec fishers put back!) as well as these youngsters.

How can no-take areas help ensure that a balance is maintained?
One way is to provide a proportion of our marine environment types with sufficient protection from extraction of resources and from discharges of contaminants. This would enable harvested stocks and the biological communities they are associated with can recover to a state closer to their natural character.

The RMA has required (since 1973)that the natural character of the coastal environment be preserved and protected from inappropriate use and development. However, in the marine part of the coastal environment, the Minister of Conservation and the Regional Councils have their hands tied by a section that prohibits them from exercising their powers in any way that might constrain the management of fisheries. (So we wonder why the 2011 State of Environment report on the Hauraki Gulf Marine Park highlights continuing decline of aquatic life and its habitats in the Gulf?)

Luckily we still have the vintage 1971 Marine Reserves Act that enables qualified community groups to apply for their own no-take marine reserves, as long as they avoid undue adverse effects on commercial fishing, adjoining landowners and recreation. So how might such reserves also contribute to redressing the balance and mitigating some of the effects of extreme maximization of fishery stock harvest?

Some of the gene-pool impacts that intensive fishing pressure can have is to select for fish that have either or both earlier age at onset of maturity and smaller size at maturity. There is also scientific debate about the effects of intensive harvest pressure (and conversely marine reserves) on the behavior and genetics associated with “site-fidelity” (stay-at-home individuals) versus “vagrancy” for the adults of some species where the spectrum of behavior suggests at least part of it is under genetic influence.

Put simply it looks like large marine reserves might help select for individuals with delayed onset of maturity (i.e. allows for growing faster and larger) and for greater site-fidelity (i.e. vagrants run away and get caught before reproducing). This would help offset some of the adverse effects on gene pools of intensive harvest pressure.


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