Conserving Biodiversity

Did anyone see the letters to the Editor in July's fishing World? Two Associate Professors gave Jim Harnwell a serve for suggesting that marine parks are there to manage fisheries. Apparently they have nothing to do with fishing - they are there to preserve 'biodiversity'. Jim Harwell gave a rather good response and I have also sent in my effort:

Marine Parks ? Fisheries Management or Biodiversity?

I read with amazement the letters to the Editor by the two University Scientists Davis and Skilleter who pointed to the portrayal of marine parks as a fisheries management tool as deliberate misinformation. Well I have news for them. Locking up large parks of the ocean (20- 40%) as marine park proponents are advocating does have implications for fisheries management. Even more to the point is the fact that marine parks are being promoted as exactly that ? a fisheries management tool ? and a superior one at that! I would point to the many papers and articles which promote gloomy and exaggerated pictures of overfishing and failure of traditional fisheries management methods. Eg there was the report by the regular Pew funding recipient Boris Worm which infamously predicted that all the World?s fish stocks will collapse by 2050. Then there was the NPA?s effort of the ?Empty Nets ? Empty Oceans? and the recent ?Torn Blue Fringe? regarding NSW fisheries. Along with similar papers following the exaggerated claims of failure to manage fisheries there is always the kicker at the end of MPA?s or no fishing areas as a solution.

The Davis and Skilleter fail to mention that even with a network of marine parks, fishing will go on in most of the ocean. We are actually obliged under UN conventions to use our marine resources or we must let foreign boats in. Marine parks will therefore not remove man?s influence given the connectivity of the ocean and the mobility of fish and their larvae. So the question must be asked how marine parks will interact with other fisheries management techniques. Whether locking up a large portion of the ocean in marine parks is better than managing the whole fishery with quotas, gear limits, trip limits for commercial fishing, closed seasons, bag limits, size limits etc is highly questionable from a fisheries management perspective as well as a biodiversity perspective. Bear in mind that Australia already has the most heavily regulated and therefore the least fished waters in the world.

Davis says that any fishing effort has an impact on biodiversity. Well I have news for him every living creature has an impact in order to survive ? human being included! Ecology is above all holistic. Fisheries, both recreation and commercial are a significant source of protein as well as having unique health benefits. They take some pressure off other forms of food production such as agriculture which have their own significant environmental impacts. Most of the fish consumed in Australia (70%) is imported from waters usually far more heavily fished than our own. NSW imports 91%. This has to be paid for with economic activity which has it?s own environmental impact. Recreational fishing is the biggest form of domestic tourism and supports jobs in other industries such as boating, tackle etc. Fishing, if not overdone, has a relatively minor impact on biodiversity compared to problems like pollution and degradation which marine parks do nothing about. It cannot be assumed that marine parks are the best way to preserve biodiversity either. From Prof Kearney?s recent review of the ?Torn Blue Fringe?:

?Further, a reduction in fishing effort is not necessarily consistent with maintaining an optimal ecologically sustainable total catch, nor can it be assumed that fishing always reduces biodiversity. There is, in fact some evidence to show that well managed fisheries can result in greater biodiversity than when fishing is restricted or where there are poorly managed or overexploited fisheries (Asch and Collie 2008), i.e that intermediate levels of disturbance increase diversity as predicted by the Intermediate Disturbance Hypothesis (Dial and Roughgarden 1998). There is no cost-effective gain for biodiversity, including that of the target species, from decreasing effort when excess effort is not the problem.?

Marine parks themselves can lead to problems for ecology and biodiversity. Fishing pressure tends to be displaced by the reserves and can lead to overfishing in the areas still open. Fish species don?t respond equally to management by reserves, eg more mobile species get less protection which can lead to changes in species assemblages. From Prof Colin Buxton?s review of existing Tasmanian marine reserves:

?Secondly, in an exploited population, introducing an MPA was equivalent to increasing the Total Allowable Catch or the effort outside the reserve. Introducing an MPA without reducing catch was likely to have negative effects upon most fisheries where adult movement was limited in extent, leading to reductions in total stock size and egg production.?

?Finally, given the assumptions of the generalized model, it appeared that it would be better to improve current management controls, in particular the match between size limits and the growth characteristics, rather than introduce large MPAs to improve the fishery.

In the Tasmanian lobster and abalone fisheries where catch and effort are effectively limited, it was concluded that the introduction of MPAs as a fisheries management tool would be inferior to present management options. Indeed, if introduced without reducing catch or effort by amounts equivalent to that in the prospective closed area, closed areas were a risky strategy that could lead to a degradation of the fishery (this appears to be a general conclusion for species with low movement rates).

Furthermore, if a fishery is being managed in accordance with ESD principles, which by definition means that the ecosystem in which it operates is not threatened by the fishery or fishing practices, then fishing should not be a key threatening process. It follows from this argument that true ESD fisheries management offers a potentially better outcome than no-take MPAs for biodiversity conservation.?

Many other scientists have also questioned the proclaimed benefits of marine parks. Refer to Prof. Ray Hilborn?s ?Faith Based Fisheries? paper which described a move to advocacy by scientists promoting marine reserves, and a complete breakdown in proper peer review concerning them in the major journals. As Prof Hilborn pointed out and advocate always knows the answer and merely looks for evidence to support it. I would encourage Davis and Skilleter to think critically like the scientists I have quoted have done. Davis talks about scientific fact, well the fact is that a scientist asks nature how much support there is for competing hypotheses, and does not start with the answer and look for evidence to support it as an advocate does.