Conservation & Sustainable Management, Marine Life

Australia’s protected area network fails to adequately protect the world’s most threatened marine fishes

Australia has, compared to some other countries, a fairly extensive network of both marine and terrestrial protected areas.  On the marine side there is of course the Great Barrier Reef Marine Park and more recently the implementation of the Commonwealth Marine Reserve network.  The idea behind any marine protected area is to offer long term “conservation of nature with associated ecosystem services and cultural values”, so one would expect to see some effective protection going on in these areas…right?  Areas chosen, and cared for to ensure they offer conservation value, to do all we can to help keep species going that have suffered population declines because of our actions?  I’m sure many of you won’t be surprised to hear that this isn’t always the case.  Take a look at some of my previous posts over on Google Plushere, here, and here for example.  Unfortunately, as highlighted in a recent study by Karen Devitt, who was based at Charles Darwin University, Australia’s protected areas are inadequate for protecting one of the world’s most threatened marine fishes – the sawfish.

There are 5 species of sawfish (Pristidae) in the world.  In a previous study focusing on sawfishNick Dulvy and fellow researchers reported that the group, which can occupy marine, brackish, and fresh water habitats at different stages in their life cycle, are probably “the world’s most imperilled marine fishes”.  Three of the five species – smalltooth sawfish (Pristis pectinata), largetooth sawfish (Pristis pristis), and green sawfish (Pristis zijsron) are classified on the IUCN Red List as critically endangered.  The remaining two species – narrow sawfish (Anoxypristis cuspidate), and dwarf sawfish (Pristis clavata) are classified as endangered.   Out of the five species of sawfish, only the smalltooth is not found in Australian waters.  More so, northern Australia is home to “some of the few remaining viable sawfish populations” in the world.  Looking after these guys isn’t just important for the Australian population of sawfish, but for the global population of sawfish.  Northern Australia’s waters is in fact, globally significant.  If northern Australia’s populations decline, then the outlook is extremely bleak for these rather unusual looking fish.

One of the key steps Karen and fellow collaborators undertook was to accurately map the range of each of the sawfish species in Australia.  They had to do this themselves because only very coarse range maps had been produced from limited data.  Sounds silly doesn’t it – a seriously threatened species, and we don’t even really know where it lives.  Understanding ranges is (rather obviously) crucial for implementing effective protected areas for these guys.  After all, a protected area situated over very little or even none of their habitats is rather pointless.  The team managed to obtain a number of records of each species that they could confidently use in their analysis.  They also used the known habitat preference of each of the 4 species and maps of Australia’s land (for the freshwater habitats they use) and sea-scapes to figure out what the most likely ranges of these endangered critters are.  Of the 2,908 records of narrow sawfish, 741 records of green sawfish, 247 records of dwarf sawfish, and 470 of large sawfish, a total of 524 records were taken within a protected area.  The percentage of range protected was also low.  For their inland (freshwater) range, between ~9 and 17% had some protection designation attached.  Their marine ranges fared a little better – around 22 – 44% some protection.

But there is something else to consider.  Not all protected areas afford equal protection.  The IUCN has a range of different categories for both terrestrial and marine protected areas.  In a marine context, at the upper end you have strong protection like areas you can’t extract things from – fishing and mining is banned.  At the lower ends you have sustainable use zones, which allow (hopefully) carefully managed activities to take place.  This can include things like fishing or mining.  When you are dealing with a species – or indeed a group of species like the sawfishes that are living in a very precarious position, ideally you want the protected areas to offer them the strongest protection possible.  Alas this is not so.  Karen and colleagues maps showed that most of the protected areas (terrestrial and marine) that covered the sawfishes ranges were sustainable use zones – zones in which activities known to be a direct threat to sawfish still take place.  What’s more, the team also note that the Commonwealth Marine Reserve network may not be all it is cracked up to be, with the current Australian Government, elected in 2013, suspending the management plans for the network.  In reality, the little protection the sawfish were supposed to be afforded by the network may be significantly eroded.

There was one final issue that the team raised in their paper – that of connectivity.  It is becoming well understood by scientists (if not politicians) that marine protected areas cannot function as single isolated islands.  Many species undertake dispersal at some time or another – the larvae of sessile organisms can travel on currents to new settlement sites for example.  Some species – like sawfishes – can travel large distances, utilizing different habitats.  An effective marine protected area may very well need to be included inside a network, and that network needs to consider how critters move around, and how in reality seemingly disconnected sites are in fact connected.  Female largetooth and dwarf sawfish for example both pup in estuaries.  Their juveniles live in freshwater and riverine habitats.  It is only when they are older that they head out into the ocean.  These seemingly disparate but essential habitats for the sawfish (and indeed many other species) has not been considered in network design.  The urgency to consider connectivity is heightened by proposals to develop hydroelectric dams in northern Australia, something that has the potential to block migrations of these critters.

In terms of size, Australia’s terrestrial and marine protected areas may be making advances in achieving targets set by the international community, but they are far from achieving any meaningful contribution towards species like sawfishes which so desperately need help.

The paper which was published in Global Ecology and Conservation has been made open access.  You can have a read of it here http://dx.doi.org/10.1016/j.gecco.2015.01.007

Image:  An x-ray of the small tooth sawfish (Pristis pectinate) taken by Sandra Raredon at the +Smithsonian, National Museum of Natural History.   You can see some other fantastic x-rays Sandra took, and read a how and why she did it over at the Smithsonian website.

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