Detecting conservation benefits of marine reserves on remote reefs of the northern GBR

Abstract

The Great Barrier Reef Marine Park (GBRMP) is the largest network of marine reserves in the world, yet little is known of the efficacy of no-fishing zones in the relatively lightly-exploited remote parts of the system (i.e., northern regions). Here, we find that the detection of reserve effects is challenging and that heterogeneity in benthic habitat composition, specifically branching coral cover, is one of the strongest driving forces of fish assemblages. As expected, the biomass of targeted fish species was generally greater (up to 5-fold) in no-take zones than in fished zones, but we found no differences between the two forms of no-take zone: ‘no-take’ versus ‘no-entry’. Strong effects of zoning were detected in the remote Far-North inshore reefs and more central outer reefs, but surprisingly fishing effects were absent in the less remote southern locations. Moreover, the biomass of highly targeted species was nearly 2-fold greater in fished areas of the Far-North than in any reserve (no-take or no-entry) further south. Despite high spatial variability in fish biomass, our results suggest that fishing pressure is greater in southern areas and that poaching within reserves may be common. Our results also suggest that fishers ‘fish the line’ as stock sizes in exploited areas decreased near larger no-take zones. Interestingly, an analysis of zoning effects on small, non-targeted fishes appeared to suggest a top-down effect from mesopredators, but was instead explained by variability in benthic composition. Thus, we demonstrate the importance of including appropriate covariates when testing for evidence of trophic cascades and reserve successes or failures.

Patterns of fish community composition and biodiversity in riverine fish sanctuaries in Bangladesh: Implications for hilsa shad conservation

“…Sarkar et al (2010) also reported similar feeding guild composition in river Ganges in India. The increase in mean trophic level by the predominance of carnivores found in our study might be an indicator of the benefit of fishing restriction (Castro-Sanguino et al, 2017;Ecoutin et al, 2014). However, it was not possible to conclusively compare our results for such impact due to lack of trophic studies of fish in these rivers or similar river in this re- , and an open fishing area (S1) in Bangladesh based on Bray-Curtis similarity of abundance.…”

Relative efficacy of three approaches to mitigate Crown-of-Thorns Starfish outbreaks on Australia’s Great Barrier Reef

“…Second, proportional change in hard coral cover over the 4.5 year period was not influenced by the zoning of a site (β = 0.06, P = 0.32), but did increase with the number of voyages to visit the site (β = 0.022, P = 0.015) (fixed effects model: R 2 = 0.21, F 2,50 = 6.49, P = 0.003; Table S3). Zoning has been linked to a range of ecosystem benefits on the GBR [40][41][42] , as well as to the potential of a reef to experience a COTS outbreak [43][44][45] . Our results provide some support for this conclusion: sites zoned with greater protection, i.e.…”

“…Zoning has been linked to a range of ecosystem benefits on the GBR 40 – 42 , as well as to the potential of a reef to experience a COTS outbreak 43 – 45 . Our results provide some support for this conclusion: sites zoned with greater protection, i.e.…”

Multi-Trophic Species Interactions Shape Seascape-Scale Coral Reef Vegetation Patterns

“…Our observations of bioturbating fishes (sweetlips and emperors) foraging in a distance-sensitive manner relative to patch reefs (Figures 1E,F) are important for two reasons. First, one of these groups (emperors) is heavily targeted by fisheries within the Great Barrier Reef (Castro-Sanguino et al, 2017), and both are common targets in other reef systems globally, particularly where other fish stocks have been previously reduced by fishing. Removing these groups from an ecosystem may therefore have consequences for habitat structure, specifically formation of halos, and subsequently sedimentary carbon storage (Atwood et al, 2018).…”