Empty seas coming to a shore near you

12 07 2012

Last week I had the pleasure of entertaining some old friends and colleagues for a writing workshop in Adelaide (don’t worry – they all came from southern Australia locations, so no massive carbon footprints for overseas travel). I’m happy to report it was a productive (and epicurean) week, but that’s not really the point of today’s post.

One of those participants was long-time colleague, Dr. Rik Buckworth. Rik and I first met in Darwin back in the early 2000s when he was lead fisheries scientist for Northern Territory Fisheries; this collaboration and friendship blossomed into an ARC Linkage Project (with Dr. Mark Meekan of AIMS) on shark fisheries (see some of the scientific outputs from that here, here, here and here). Rik has since moved to CSIRO in Brisbane, but keeps a hand in NT fisheries’ affairs. Incidentally, Rik trained under one of the most well-known fisheries modellers in the world – Carl Walters – when he did his PhD at the University of British Columbia back in the early 1990s.

During our workshop, Rik pointed out a paper he had co-authored back in 2009 in Reviews in Fish Biology and Fisheries that had completely escaped my attention – it’s a frightening and apocalyptic view of the Australasian marine tropics that seems to confirm our predictions about northern Australia’s marine future. Just take a look at the following two figures from their paper (Elasmobranchs in southern Indonesian fisheries: the fisheries, the status of the stocks and management options):

The left-hand maps are the catch rates of sharks in the Java Sea (north of Java, Indonesia), and the right-hand images are catch rates of rays. The top panels represent data collected during cruises done in 1976, and the bottom maps show the same area in 1997.

Take a good, close look – anything jump out? Unless you’re officially blind, you’ll notice the stunning reduction in shark and ray abundance over the 20-year period (it works out to be about a 90 % reduction in biomass). No, ‘stunning’ isn’t strong enough – ‘catastrophic’ is more à propos. Personally, I uttered something more like “holy f&%k!” when I first saw these figures.

CB readers might recall another paper also published in 2009 (of which Rik was a co-author) where we examined shark declines in fished and unfished reefs in Australia’s northern Exclusive Economic Zone – we found evidence for shark declines then, and predicted that the continued penetration of illegal fisheries into waters to our north would eventually wipe out Australian shark & ray populations. We called this phenomenon the “protein mining wave”.

In summary, we can probably expect northern Australia’s shark and ray populations to look a lot like the above figures if we don’t get a serious handle on illegal fishing in our EEZ. Some might say that’s an impossible task. For the sake of our marine biodiversity, I hope not.

Currently, Indonesia is the world’s largest commercial fishing nation for sharks, but this is made worse by a lot of Chinese- and other nation-financed fishing in the region, including support of illegal operations. Efforts to highlight this frightening phenomenon to the region’s politicians are therefore advisable.

CJA Bradshaw


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