Gau Island, Fiji S17°56.60' E179°15.90' Reef Report
Health of Gau Island Reef, Fiji
Gau Island

Aug 11th, 2007 - Aug 17th, 2007

Reef type:

Gau Island has a fringing reef on its north and east coasts with a barrier reef off its west and south coasts creating a large lagoon. Our study site was the fringing reef off the north-west coast. We studied two zones of this fringing reef, one inside a recently declared Marine Protected Area (MPA), the other just outside the MPA.


Gau Island is located 90 km east of Fiji’s largest island, Viti Levu. The land, its fringing reef and the lagoon/barrier reef system are managed as a whole. Gau and its waters are divided into 18 regional communities. The study site for our data was located in the waters off the northwestern community of Qarani.

Slash and burn practices
The lush mountainous environment of Gau has been subject to poor land management practices, including slash and burn, which lead to increases in sedimentation levels and decreases in hard coral cover of the fringing, barrier, and patch reefs around the island. While the use of fertilizers on Gau is low, high levels of nitrification in the water are apparent from overgrowth by macroalgae in some areas, most likely due to a lack of sewage treatment. Small boat traffic is heavy in the area. In the community of Qarani, impacts from fishing by handline and spearfishing are minimal. (Brown, L.F, 2006)

The north and northwest coasts are protected from the south east trade winds which blow from April/May to September/October.


A major bleaching event, possibly from increased water temperatures, occurred in Fiji in 2000, decimating an average of 40-80% of hard corals throughout the islands. (Sykes 2007) Gau Island was adversely affected from the bleaching event and damaged even further by outbreaks of crown of thorns stars in 2001 and 2002. These afflictions were observed specifically by Helen Sykes at the site Anthias Avenue, just inside the pass on the northwest side of the lagoon but were most likely affecting many other parts of the Gau reef system. Recently there has been amplified concern of the sustainability of Gau’s fish and invertebrate populations.

Sawaieke village
With support from Fijian and South Pacific partner organizations, Gau has recently become a part of the Locally Managed Marine Area Network (LMMA) of Fiji. This network is unique. Unlike normal marine protected areas managed at a government level, the LMMA returns the responsibility for conservation and management to the community level where the chiefs and mataqali (council of traditional landowners) have control. Reverting to this traditional management technique has proved to be very successful in protecting and improving fish stocks and coral reef health in Fiji. The LMMA in Gau Island has helped to establish at least one no-take zone in each of the 18 communities. An island assembly of elders and other community members, called the Lomani’Gau, oversee the LMMA and the protection of the island’s marine resources. (Brown, L.F, 2006)

This was a particularly appropriate time to collect data just off Qarani because it represents a baseline data set inside and just outside the recently established MPA. Frontier Fiji have a research programme based on the west side of the island and are conducting underwater surveys around the island. We hope that there are marked changes in these data sets over time as the effects of protecting the area become evident.

Water Temperature:

The water temperature averaged 75.7°F (24.3°C), with the highest recorded temperature 78.8°F (26°C) and the lowest 71.6°F (22°C).


Bleaching observations were minimal at 0.4% inside the MPA and 0.9% outside.

Lethal Orange Disease

Observations of White Band Disease occurred sporadically throughout the study site. This affected table Acropora colonies and was a possible cause of completely dead table Acropora colonies noted. Also observed was one incidence of Lethal Orange disease, in this case wasting coralline algae to leave exposed coral rock.


Horizontal visibility measurements were taken four times during the course of the study using a Secchi disk with an average value of 92 feet (30.7 metres). Nine vertical measurements gave an average value of 74.6 feet (24.9 metres).

Reef topography:
Reef topography at surface
showing ridges separated by channels

The fringing reef just off Qarani and the northwest coast of Gau extends as a reef flat which is exposed at low tide. The reef edge drops vertically to a depth of 3-4 metres. This edge is generally rich in coral cover. The reef then forms a series of coral ridges running perpendicular to the coastline with channels of rubble, rock and sand in between. The tops of these ridges are generally rich in coral cover and are in a depth of less than 1 metre at low tide. This formation of ridges and channels continues down the reef slope before dropping off into deep water. The surrounding waters reach depths of 200 metres.

Coral Observations:
Dense coral cover on ridges

We collected data within the Marine Protected Area and outside the Marine Protected area. Interestingly, the MPA zone is slightly lower in overall health than the non-MPA zone - 52.5% and 58.6% respectively - and the overall threat is higher in the MPA zone than the non-MPA zone - 35.8% and 29.1% respectively. The Vitareef dives within the MPA zone included three dives just in front of Qarani village. Here we found a higher sediment load, both in the water column and on the corals themselves, causing death of the underlying tissue. There was also more macro and filamentous algae present in this area, most likely due to a lack of sewage treatment in the village. These three dive sites are recessed into the bay, compared with the rest of the Vitareef dive sites, both inside and outside the MPA, which are on the seaward areas of the reef.

There are areas on this reef where large swathes of corals have died at least several years ago, possibly during the bleaching event of 2000. Young colonies are also establishing themselves along this reef. Acropora spp. is the dominant coral genus, particularly on the shallow reef top areas.

Fish Observations:

On the first transect dive a giant moray eel guarded a coral bommie, surrounded by schools of chromis. Two-spine, regal and lemon peel angelfish were present on each of the four transect dives. No sharks were observed during the course of this study. Few large predatory fish were observed and all groupers sighted were small, maximum 12 inches. From SV Infinity we observed many birds feeding in deeper water off the reef, indicating schools of fish present. On two occasions, schools of fusiliers were seen and lone jacks made a few appearances on the study site.
In terms of fish populations and diversity, there was no striking difference between the two areas, inside and outside the MPA. Both areas had reasonable diversity in damsel fish and small wrasse species. On three occasions during the study, Napoleon Wrasse were sighted. Judging from other dives during the course of the study, these transect observations represent the fish population of the area well. It is to be hoped that there will be an increase in diversity and predatory presence over time as the MPA establishes itself. The MPA excludes any form of fishing within the protected zone.

Invertebrate Observations:
Chromodoris lochi

Inside the MPA, there was a wide variety of soft corals that overtook much of the reef, but the most abundant were Sarcophyton spp. and Lobophyton spp. Outside the MPA, the same soft corals were present but not in as high abundance. A pin cushion star, Culcita novaeguineae, was found inside the MPA. The MPA had sea urchins, the dominant species being Echinostrephus spp. 85% of the sea cucumbers observed during this study were found within the MPA and over 50% were of the Bohadschia species. All of the observed giant clams were outside the MPA. One corallivorous snail, Conus marmoreus, was found outside the MPA and was approximately 5 cm in length.

Marine Mammals:

According to local reports, dolphins are often seen feeding outside the reef. On one occasion during the study we heard cetaceans during a dive and the dive tender observed a pod of Pilot whales passing very close to the reef. They appeared to be feeding.


Turtles were observed on four separate occasions during dives both inside and outside the MPA. All were Hawksbill turtles, between 50 and 80 cm in length.

Threats to the Reef:

Reef shallows
There are signs of this reef having been adversely affected in the past. Previous studies here witnessed both bleaching events and crown of thorns outbreaks. Pointcount data shows that the dominant bottom composition is coral rock - long dead coral covered with fine filamentous algae. This is categorised in Pointcount in the 'other' category and contributes greatly to the results of 57.9% 'other' inside the MPA and 53.8% 'other' outside the MPA. This substrate does not invite recuitment of new coral colonies, however, we did observe some new colonies throughout the area. In general, the possibility of recruitment in the area studied is inhibited by this reef lying on the leeward side of the island of Gau.

In general it can be said that the site studied is showing signs of recovery from past events which have affected its health and vitality. This is particularly evident on the reef flats and reef crests where table Acropora spp. dominate. The area of reef studied close to the village was definitely more affected by sediment and algae than the outer reef areas. We observed fires burning on the land during the first days of the study. This creates exposed soil that is easily washed off into the shallows where it tends to smother living coral. A lack of sewage management is the most likely cause for overgrowth by macroalgae.

It will be important to continue monitoring this site and to observe changes over time between the reefs inside and outside the Marine Protected Area.

We would like to thank everyone at the University of South Pacific for their assistance in enabling us to carry out this study in Gau, in particular, Dr Joeli Veitayaki, Dr Bill Aalbersberg and Dr Ken MacKay. We would also like to thank our friends in Gau Island who helped us during our time there.

Brown, Lesley F. (unpublished) 2006. Initial Assessment of the fringing reefs of Western Gau. Frontier-Fiji. International Ocean Institute, Pacific Islands.
Sykes, Helen R. (unpublished) 2007. Status of Coral Reefs in the Fiji Islands 2006. Global Coral Reef Montioring Network, Fiji Coral Reef Monitoring Network, Reef Check Fiji.
Reef Report
Vitareef Data
Species ID
GPS Data