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Individual study: The effect of rock pile design in the rehabilitation of coral reef damaged by blast fishing, Komodo National Park, Nusa Tenggara archipelago, Indonesia

Published source details

Fox H., Mous P.J., Pet J.S., Muljadi A.H. & Caldwell R.L. (2005) Experimental assessment of coral reef rehabilitation following blast fishing. Conservation Biology, 19, 98-107

Summary

Throughout the coral reefs of South-east Asia there has been extensive coral damage due to illegal fishing with explosives, termed blast or dynamite fishing. An explosive device is thrown into the water above a reef. The explosion kills or stuns fish, which float to the waters surface, but it also shatters coral skeletons on the reef below. As a further problem, areas of broken coral shift in the water currents abrading or covering new coral colonies, which slows or prevents reef recovery. In this study, the effectiveness of four rock pile designs on coral reef rehabilitation was investigated.

Study site: The study was undertaken in the Komodo National Park around several larger and smaller islands in the Nusa Tenggara archipelago of Indonesia.

Four blast sites were selected, and one replicate of each of four rock pile designs (each 140 m³ in volume) was installed at every site from March to September 2002. At each site there was also a coral rubble control. Rock pile designs were as follows:

1) Complete coverage of rocks built ~75 cm high.

2) Rock piles of 1-2 m³ spaced every 2-3 m.

3) 'Spur and groove' morphology, with ridges and valleys, parallel to the prevailing current.

4) Spur and groove morphology, perpendicular to the prevailing current.

Monitoring: Sites were monitored in March 2003. The area covered by the treatments was measured. Using a video recorded, transects were filmed to ascertain coral cover on each treatment and the control. Also, coral recruitment (number, size, life-form and taxon of all hard (scleractinian) corals) was surveyed in six 1 x 1 m quadrats. Only one treatment was surveyed per site, and a treatment was not repeat surveyed at another site. Finally, a stationary video ‘point-counts’ were used to assess fish populations at each treatment and control plot.

Hard coral recruits: Hard coral recruits quickly settled on rock piles, and after 1 year there was a average of 7.3 recruits/m² and a average coral size of 7.5 cm² across all sites.

Fish populations: There was a higher number and diversity of fish on rock treatments than the coral rubble controls. Taxa present included: grouper (Serranidae), anthias (Anthiinae), damselfish and chromis (Pomacentridae), surgeonfish (Acanthuridae), parrotfish (Scaridae), stonefish (Scorpaenidae), fusilirs (Caesionidae), and moorish idols Zanclus cornutus.

Conclusions: Rock piles were successful in aiding hard coral growth and therefore reef rehabilitation. Furthermore, rock piles had a positive effect on fish populations, with far more present at rock piles than control sites. However, there was no clear differences between the rock pile designs in this experiment, perhaps due to the short length of post-rock pile creation monitoring.


Note: If using or referring to this published study please read and quote the original paper, this is available at: http://www.blackwellpublishing.com/journal.asp?ref=0888-8892