Protected Great Barrier Reef zones benefit fish even at the relatively lightly-fished northern reefs, a University of Queensland-led international study has revealed.

The Australian Great Barrier Reef Marine Park is the largest network of marine reserves in the world, and includes both “no fishing” (no-take) and “no-entry” zones, as well as fished areas.

School of Biological Sciences researcher Dr Carolina Castro-Sanguino said the study found that fish biomass was up to five times greater in some protected zones which prevented fishing, whether they had no-take or no-entry policies.

The most remote northern reefs had greater fish biomass than more southern zones, regardless of the policies,” she said.

Dr Castro-Sanguino and colleagues analysed the policies’ effects in the relatively lightly-fished northernmost regions. They measured, counted and calculated the biomass of commonly-fished species at 31 northern, central and southern reefs north of Cooktown and assessed the seabed.

The authors found indication that fishers may operate at reserves' boundaries to exploit the increased fish biomass in these reserves, leading to a reduction of biomass just outside reserves. 

The researchers found differences in biomass between protected and unprotected areas, despite the strong effect of the seabed habitat on fish abundance, and despite this region being generally fished relatively lightly.

Dr Castro-Sanguino said this illustrated the high sensitivity to fishing of many species, reinforcing the case for their protection.    

“This study is important because it shows that marine reserves can achieve high fish biomass compared to surrounding fishing grounds, even in reef areas under moderate fishing pressure,” she said.

“It also reveals the difficulty of measuring the performance of marine reserves without considering reef habitats, and fishing distribution, including possible intensification of fishing in nearby reserves.

“This will ensure that a sound and credible base of evidence is available to assess the impact of current management.”

The study, Detecting conservation benefits of marine reserves on remote reefs of the northern GBR, is published in PLOS ONE (doi: 10.1371/journal.pone.0186146).

It also involved researchers from the ARC Centre of Excellence for Coral Reef Studies; Khaled bin Sultan Living Oceans Foundation, US; University of the Philippines; State of Hawai’i Division of Aquatic Resources; University of Western Australia; University of Melbourne; Wildlife Marine, Western Australia; Curtin University; and University of Technology, Sydney.

Media: Carolina Castro-Sanguino, cc.sanguino@uq.net.au, Prof. Peter Mumby p.j.mumby@uq.edu.au ph: +61 733 651 671

Images:  © Jeurgen Freud, iLCP

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