The science of sustainable seafood, explained

What are the Impacts of Trawling in Australia?

Recently, a group of scientists measured and mapped the extent of trawling in Australian waters in a recent paper. Lead author Tessa Mazor provided the below commentary for CFood UW.

We also encourage you to check out this blog post from Mazor’s institution.

5 surprising statistics about trawling

  1. Less than 5% of Australia’s EEZ waters are trawled
  2. 58% of Australia’s EEZ is protected from trawl fishing
  3. On average, 7% of each invertebrate community studied are in trawled areas
  4. On average, 38% of each invertebrate community studied are protected from trawling
  5. On average, 55% of each invertebrate community studied are not trawled or protected.

Comment by Tessa Mazor, CSIRO Brisbane

Sustaining seabed fauna is critically important for marine ecosystem processes. In our paper we provide the most extensive assessment of the current trawl fishing exposure of benthic invertebrates across Australia’s waters. This work responds to the global need to quantify and address the broad scale impacts of trawl fishing on the seabed. Such information is greatly in demand by a range of stakeholders, such as fishery managers and industries aiming to adhere to sustainable certification commitments, conservation planners designing protected areas and decision makers setting national environmental agenda and policy. We aimed to quantify trawl exposure and protection of benthic invertebrates at large-scales, including developing a method that integrates data from disparate seabed surveys to spatially expand predicted distributions. We incorporate data from 18 seabed surveys to map the abundance distribution of benthic invertebrates in 9 regions within the Australian Exclusive Economic Zone.

Our approach combines disparate benthic survey data, groups taxa having similar distributions within taxonomic class, and uses Random Forests to predict group distributions from environmental variables. Exposure and protection are quantified by overlapping predicted abundance distributions of benthic invertebrate groups with maps of trawl-footprint, marine reserves and fishery closures. We found that more of Australia’s EEZ is currently protected from trawling (58%) than is exposed (<5%). Across all regions, 96% of benthic invertebrate groups had greater abundance protected than exposed to trawling. The mean exposure of benthic invertebrate abundance to trawling was 7%, compared to mean protection of 38% — further, 55% was neither exposed nor protected. Fishery closures, covering 19% less area than marine reserves, overlapped with a higher mean proportion of predicted benthic abundance; thus, highlighting the contribution of fishery closures to marine conservation.

Furthermore our study demonstrates how disparate seabed surveys can be combined equitably to support regional assessments of benthic invertebrates. This study is widely applicable elsewhere and for a range of other taxa, helping decision makers: identify taxa and regions that are at higher risk of disturbance, determine the effectiveness of current protection measures, and guide the placement of future protection measures. Such analyses can help managers achieve more sustainable industries and marine ecosystems.

Tessa Mazor is a Postdoctoral Fellow at CSIRO Brisbane. You can follow her on twitter here.

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