Get Regular Updates!
Search
|A prawn tale: winners and losers in climate change

Earth

image|CSIRO A prawn tale: winners and losers in climate change

A prawn tale: winners and losers in climate change

Who booms, and who goes bust?

A prawn tale: winners and losers in climate change

Climate change is never cut and dried (or cut and flooded, depending on where you live).

It’s complicated, and we don’t fully understand how it’ll affect our planet. There can be good and bad things that come out of it.

Of course, depending on whether you’re a delicious crustacean or a human, good and bad outcomes mean entirely different things—I’ll get to that in a bit.

First, let me tell you about a heatwave that put Fury Road to shame.

THE EXTREME MARINE HEATWAVE OF 2010/11

You think 3 days in a row over 40°C is bad? Try 3 whole months.

From December 2010 to February 2011, the sea surface temperature off our coast was, on average, 4 to 5°C above normal.

View Larger
Image|DPIRD
The sea surface temperature was well above average between December 2010 and February 2011

Even 100 metres under water, you could still feel it.

The effects of the heatwave on our marine ecosystems are still being worked out by scientists. Some organisms will never recover from the heatwave. For others, it’s been a rollercoaster ride back to relative normalcy.

Take the humble prawn.

A TALE OF TIGERS AND KINGS

Aside from their role in advertising Aussie tourism, prawns are big business in WA.

Shark Bay is home to our largest prawn fishery, which harvests the western king prawn and the brown tiger prawn.

About 700km north, the Exmouth Gulf hosts the second largest prawn fishery. Like Shark Bay, the boats are mostly there for the tigers and kings.

In 2014, the Shark Bay prawn fishery was valued at $25 million, with the Exmouth Gulf fishery coming in at $6 million. The entire prawn haul for that year was 2,000,000kg.

No small beans.

View Larger
Image|Tama Leaver
The market demand for prawns in WA is well established, as well as around the world

So lucrative were prawns in the 1980s that overfishing threatened both species in both locations. Thankfully, the Fisheries Department (now the Department of Primary Industries and Regional Development) was able to put in place management strategies that ensured both Shark Bay and Exmouth were able to develop into lasting, sustainable fisheries.

HEAVY WEATHER

These fisheries have felt the effects of extreme climate before—both good and bad.

In 1975, Cyclone Rita passed by Exmouth and stirred the pot—in a very good way. Following the storm, scientists reported that brown tiger prawns were present in record numbers. They believe Rita’s visit made some waves, disturbed the seabed and put more prawn food in the water column.

25 years later came Cyclone Vance. One of six cyclones that season, Vance’s eye straddled the gulf that housed the fishery and cut a line straight down the middle. Wind speeds greater than 200km an hour ripped apart seagrass nurseries, leaving baby prawns defenceless against the elements and hungry fish.

Cyclone Vance was one of the most devastating cyclones Australia has ever seen

When the number of young prawns is low, continued fishing of the animals can cause the fishery to collapse.

Luckily, the Fisheries Department had it covered and put appropriate restrictions in place.

In fact, they’ve had it so well covered that, in October 2015, both the Shark Bay and Exmouth Gulf prawn fisheries achieved the Marine Stewardship Council’s eco-tick. It’s like the Oscars of third-party sustainable fisheries certification.

WINNERS AND LOSERS, MOVERS AND SHAKERS

Unfortunately, all the restrictions and certifications in the world can’t shield us from the global impact of climate change.

In the summer of 2010, weird winds in the western Pacific combined with reduced southerly winds off the southwest of WA created a powerful current that brought tropical water streaming down our coastline. Combine this with an intense La Niña period, and you’ve got yourself the mother of all heatwaves.

And just like the cyclones, it brought both good and bad impacts.

HITTING THE WATER

In Shark Bay, both the kings and tigers had record high seasons in 2011. Scientists presume that this was because the water in Shark Bay is approximately 2°C cooler than in Exmouth, so the heatwave likely bumped it up to a more agreeable temperature for the prawns.

Interestingly, the years that followed the great heatwave also saw above-average temperatures and yet prawn populations returned to normal size.

Up in Exmouth where the waters are typically more tropical, the extra few degrees seemed to make king prawns suffer. 2011 saw a huge drop in population size. Scientists aren’t sure exactly why. Did the temperatures affect the prawns themselves? Their behaviour? Their physiology? Or did it affect their food source?

Whatever it was, it seemed to only affect king prawns. Tiger prawns in the Exmouth Gulf had a bumper season in 2011, with one of the highest catches of new young prawns ever recorded.

View Larger
Image|Heather Dine
Seagrass meadows like this are used by prawns as nurseries. Unfortunately, they can be badly affected by changes in water temperature

But once again, it was a different story in 2012. While the Exmouth tiger prawns thrived during the heatwave, the sea grass had suffered. Leaves were lost, flowers collapsed, seeds aborted, which meant that the prawns’ nursery habitat was once again destroyed, indirectly leading to a collapse in stock numbers.

These detrimental effects on the Exmouth tiger prawns appear to be longer lasting than any other impact on prawn populations, but the tiger prawn fishery is now fully recovered.

SCIENTISTS LEADING THE BLIND

Clearly, there’s much to understand about the effects of climate change on our planet. There’s a lot we don’t know.

But there is one thing that we can find out.

We can find out (roughly) how many prawns are in the water, and we can estimate how many prawn babies they’ll have next season.

Since the great heatwave (and for a long time before it), the Fisheries Department has been surveying the seas, counting crustaceans and doing what they can to make sure we don’t double down on climate-caused catastrophes.

View Larger
Image|Sam Wilson
RV Naturaliste is the Fisheries Department's purpose built research vessel

The efforts of scientists to monitor, detect and manage accordingly is one of the only ways that we can move forward with some sense of reasonable understanding.

Probing ahead a little at a time, science is the proverbial white cane to our collective blind person. It helps us move forward inch by inch without letting us walk off the curb into the oncoming traffic that’s about to take us out.

With climate change events more and more likely to flatten us in the future, now, more than ever, we need advice from our friends in the fisheries—and we need to follow it.

Two blood cells met and fell in love.. VIDEO

Republish

Creative Commons Logo

Republishing our content

We want our stories to be shared and seen by as many people as possible.

Therefore, unless it says otherwise, copyright on the stories on Particle belongs to Scitech and they are published under a Creative Commons Attribution-NoDerivatives 4.0 International License.

This allows you to republish our articles online or in print for free. You just need to credit us and link to us, and you can’t edit our material or sell it separately.

Using the ‘republish’ button on our website is the easiest way to meet our guidelines.

Guidelines

You cannot edit the article.

When republishing, you have to credit our authors, ideally in the byline. You have to credit Particle with a link back to the original publication on Particle.

If you’re republishing online, you must use our pageview counter, link to us and include links from our story. Our page view counter is a small pixel-ping (invisible to the eye) that allows us to know when our content is republished. It’s a condition of our guidelines that you include our counter. If you use the ‘republish’ then you’ll capture our page counter.

If you’re republishing in print, please email us to let us so we know about it (we get very proud to see our work republished) and you must include the Particle logo next to the credits. Download logo here.

If you wish to republish all our stories, please contact us directly to discuss this opportunity.

Images

Most of the images used on Particle are copyright of the photographer who made them.

It is your responsibility to confirm that you’re licensed to republish images in our articles.

Video

All Particle videos can be accessed through YouTube under the Standard YouTube Licence.

The Standard YouTube licence

  1. This licence is ‘All Rights Reserved’, granting provisions for YouTube to display the content, and YouTube’s visitors to stream the content. This means that the content may be streamed from YouTube but specifically forbids downloading, adaptation, and redistribution, except where otherwise licensed. When uploading your content to YouTube it will automatically use the Standard YouTube licence. You can check this by clicking on Advanced Settings and looking at the dropdown box ‘License and rights ownership’.
  2. When a user is uploading a video he has license options that he can choose from. The first option is “standard YouTube License” which means that you grant the broadcasting rights to YouTube. This essentially means that your video can only be accessed from YouTube for watching purpose and cannot be reproduced or distributed in any other form without your consent.

Contact

For more information about using our content, email us: particle@scitech.org.au

Copy this HTML into your CMS
Press Ctrl+C to copy

We've got chemistry. Want something physical?