How healthy are our recovering fisheries?

HOW healthy are fisheries in Australian waters? This blog article published online by takes a detailed look at how the past can greatly affect the future of fisheries in this country. 

Shifting baselines: how healthy are our recovering fisheries?
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One of the problems when assessing the health of fisheries is that we get used to how they are now or how they were when we started fishing them, we don’t view them in the context of their historical abundance. The baseline shifts, so instead of comparing the abundance of fish to the long term abundance of the stock, each generation redefines what “natural” or “healthy” fish stocks are as they continue to decline each generation.

Daniel Pauly first introduced the idea of shifting baselines in fisheries management, showing that shifting baselines can mask drastic declines in fish stocks over the long term (his TED talk on the topic is worth watching if you aren’t acquainted with the idea). It can also effect how anglers think about fish stocks that are recovering, especially stocks that have drastically declined with only a small fraction of the pre-fished biomass remaining.

There are a number of fish stocks around the country that are well well below historical levels. Two that are most pertinent when it comes to how shifting baselines affect how we perceive fisheries that are in the process of recovering are the Southern Bluefin Tuna fishery and the Murray cod fishery.

In the case of Southern Bluefin tuna, less than a decade ago it was estimated that the stock was at a mere 5% of pre-fished spawning biomass. That’s LOW! In the last decade, reduction in quotas have seen the stock bounce back slightly. The stock is now estimated to be at 9% of pre-fished spawning biomass, with the biomass of 10+ year old fish increasing from 5 to 7% between 2011 and 2014. This is great news, there are signs that Southern Bluefin are making a comeback!

The problem comes from some within the angling and commercial fishing communities, seeing and experiencing this recovery first hand thinking that everything it now hunky dory, that quotas should be increased and bag limits upped (potentially stalling or slowing the recovery that has really only just begun). The low abundance of the fish now perceived as normal, the small recovery as a “boom”. This is shifting baselines in action.

Southern Bluefin stocks still aren’t in great nick, they are still ONLY at 9% of pre-fished spawning biomass. So while the fishing has improved and it seems that the fishing is the “best its ever been”, thats only because as a community, we’ve forgotten how good it was a generation ago, 30-40 year ago. The baseline has shifted. We have forgotten what we have lost. We have forgotten how good our fishery should be.

The same goes for Murray cod. Its estimated that Native fish populations in the Murray Darling basin are at less than 10% of their original levels. This is potentially a vast over-estimate, with scientist such as Paul Humphries suggesting that the real figure is likely closer to 1%, thats REALLY low (you can check out a video about his genius pub crawling “Stuffed Murray cod in Pubs” project here).

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Read full article HERE.

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