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Individual study: Experimental rehabilitation of coral reefs 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 effect of three cost effective reef rehabilitation methods: rock piles, cement slabs and netting pinned to rubble, on coral colonisation 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.

Restoration plots and  treatments: Nine blast sites were selected, within which 1 x 1 m treatment and control plots were established. At each site, two to four replicate plots of each treatment were created using locally and readily available materials:

1) Rock piles – rocks of 20-30 cm diameter were used to make a 20-40 cm high pile on top of the rubble.

2) Cement slabs – slabs were pinned to remnant coral rubble.

3) Netting – wide-mesh fishing net (5 cm mesh) was attached to remnant coral rubble with U-shaped re-bar pins.

Additionally, four untreated coral rubble control plots were created. Plots were created at three sites in March and April 1998, and at six sites in October and November 1998.

Monitoring: Sites were measured every six months until Spring 2001. The location, size, life-form, and taxon of all hard corals colonising the plots were recorded. Additionally, cover of soft coral and other dominant benthos was estimated.

Coral growth: During the first three years, the rock stabilisation plots had the highest hard coral recruitment and cover, followed by cement slabs and netting. After two and a half years, some coral colonies were 20-30 cm in diameter on rock piles and cement slabs. In contrast, in the untreated coral rubble control plots the number and area covered by hard coral did not increase over the study period.

Treatment degradation: Over the course of the experiment many treatment plots became degraded: many netting plots were scoured or buried by shifting rubble, some rock piles were scattered and cement slabs turned over by the current. All treatments had at least some growth of soft corals.

Conclusions: The results suggest that addition of rock piles to blast damaged reefs provides the best substrate for colonisation by hard coral growth. However, the small size of rock piles in this experiment meant that currents degraded the rock piles.


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