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Current Health of the Great Astrolabe Reef, Kadavu Island, Fiji


 

By Jessy Paquette

For a .pdf version of Jessy's report  click here.

Background

Kadavu is a remote island that lies about 100 km south off the main island of Viti Levu. It is rugged, almost 60 km in length and 14 km wide, with high volcanic peaks, rolling hills and many indented bays. The world famous Great Astrolabe Reef stretches for 30km off the north east coast of Kadavu extending north beyond Ono Island. It boasts outstanding hard corals, caves, wrecks and a fantastic array of marine life due to its rich currents (1). However, this natural wonder is under constant thread. Greater surface seas temperatures (SSTs), pollution, over fishing, parasites and other nuisances can destroy corals and leads to reef deterioration (2). Furthermore, coral reefs represent crucial sources of income and resources through their role in tourism, fishing, building materials, coastal protection and are an excellent source for pharmaceutical research. Consequently, the current health of the biota on the Great Astrolabe Reef needs to me monitored to evaluate the rate of deterioration (is there is) to assure that this natural wonder is conserved for future generations.

Study Area

The Great Astrolabe Reef, which is approximately 65 km in length, is located roughly 100 km south of Suva, the capital of Fiji. The reef lays on the east coast of Kadavu, the fourth largest island Fijian group. The Waisalima Beach Resort & Dive Center is located on the eastern end of Kadavu Island, close to Ono Island, nestled in its own secluded bay between Tiliva and Lagalevu villages facing the Great Astrolabe Reef. This reef is very important since it is an important source of food and revenue for the locals. This diversified ecosystem is also the home of a great variety of tropical and pelagic fishes and corals.


View Jessy's Map in a larger map

Methodology

Ten sites where visited and analyzed. On deep sites SCUBA technology was utilized and on sallow sites mask, fins and snorkels where used. A visual inspection of the reef was done and some digital pictures/videos where also taken. GPS locations where collected to allow future researchers to survey and analyze the same areas. Furthermore, local fishermen and dive masters where interviewed to evaluate the past health of the reef. Finally, all this information was used to create a KMZ of the healthy and unhealthy spots on the Great Astrolabe Reef (to see if there was a geographical pattern of deterioration) which should be monitored by scientists and local authorities.

Results

Here are the major findings of the Great Astrolabe Reef survey:

  • Site #2 “Manta rays”: This site was very nice with minimal sings of human or climate damage. Hopefully, villagers will limit the number of visits (this is quick becoming a major attraction in Ono Island) to avoid too much interference with the manta’s routine. Also, tourist should be informed not to stand on coral heads and not to touch the flora and fauna.
  • Site #3 “Japanese garden” and Site #4 “Beacon reef”: Theses sites are pristine because villages have created a MPA (Marine Protected Area) around the areas. Therefore, no fishing is allowed so fish can reproduce and colonize the areas that where deteriorate around the MPA.
  • Site #5 “Archway” and #6 “Turtle’s lair”: Theses sites are as unspoiled as it gets. There are no signs of bleaching or deterioration and fish life is abundant. Big breakers prevent fishing and diving on most days (protecting fauna and flora). Theses activities can only be attempted when the weather is good and tides are high or the boat will get smashed against the reef.
  • Site #7 “Pool 1”and Site #8 “Pool 2”: According to local fishermen the two pools where fished extensively (since they where easily accessible). One even said that dynamite fishing was employed. This may explain the large amount of coral ruble found on the bottom and the absence of lager fishes. One Crown of Torn (COT) (a coral eater) was also found in the first pool. Large amounts of filamentous algae was observed probably due to the lack of grazers like parrot fish (they where also fished-out). According to are guide (also a fisherman), fish numbers are up from 2001. This reef is slowly coming back to life after being under huge amounts of stress.
  • Site #9 “Waisalima intertidal zone”: About 20 meters off the resort's beach. This area is exposed or very sallow when the tide is out. Found a Lionfish in the sea grass which is very uncommon. This part of the bay looks healthy, but is not very interesting for snorkelers.
  • Site #10 “Waisalima House Reef”: About 50 meters off the resort's beach. This area is not exposed when the tide is out. There is a lot of eutrophication and coral damage. Only a few fish can be found. The ecosystem was clearly deteriorated probably due to overfishing and storm damage. This part of the bay is unhealthy and not very interesting.
  • Site #11 “Ancestors point”: This site is about 800 meters south west of the resort's beach around the nearest point. Since there is an accident burial site next to it, people are not allowed to fish there. Therefore, the reef is pristine with heaps of healthy coral and fish.

Conclusion

We concluded that climate change is not a current threat for the Great Astrolabe Reef. Stronger storms, cause by greater climate variability, could damage the upper part of the reef but this hypothesis needs to be confirmed. Furthermore, according to locals, surface seas temperatures (SSTs) seem to be constant. This is probably caused by the bathymetry: deep water comes into the lagoon two times a day and cools down the surface water which prevents coral bleaching. On the other hand, man made damage was observed on some sites. In all, the Great Astrolabe Reef is showing only minor sings deterioration. With proper monitoring and sustainable fisheries/tourism practices this natural wonder could be easily conserved for future generations.

References

(1)    http://www.pacific-travel-guides.com/fiji-islands/travel-guide/southern.html [Accessed 10/05/2011]

(2)    IPCC, (2007). Climate Change 2007: The Physical Science Basis (summary), IPCC


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