Monday, October 11, 2010

Fiji Expedition: Something's Fishy at Mt. Mutiny

Mt. Mutiny - Oct 10, 2010, 7 a.m.
As I peered down from the summit of Mt. Mutiny, my world was awash in color. Brilliant magenta soft coral polyps extended to pull the plankton from the water column. Hard corals in shades of purple, turquoise, pinks and even neon orange fought for territory for the precious little space on the seamount surrounded by an abyss of blue water down to 3,000 feet. [Note: For more background on seamounts, read this post.] Yet despite the stunning natural beauty of the coral communities, all was not well on the mountain.

Corals abound on the summit of Mt. Mutiny. (Photo: Keith Ellenbogen)

A reef with such dense coral fauna and structural complexity should be teeming with fish. In an intact system, the small filter feeders, such as the brilliant orange and purple anthias dotting the reef walls, attract larger prey species such as grouper and emperor, while sharks silently prowl below and schooling barracuda hover above. But here on Mt. Mutiny, the top part of the food chain has been severed.

Although the NAI'A crew say that they have not encountered fishing boats on this site, they must slip in unsighted when no other ships are around to reap their bounty. Based on my observations, the gear of choice is probably spearguns. At night, large parrotfish and surgeonfish become sitting ducks, so to speak, as they sleep among shallow reef crevices. They are easily picked off by spearfishers in large quantities.

Coral fan garden on the flanks of Mt. Mutiny (Photo: Keith Ellenbogen)

But in typical Darwinian fashion, the survivors adapt. In this race of survival of the fittest, the fittest fish, those that live to see the next group of NAI'A divers, are those that have taken refuge in depths below the 100 ft. These depths are inaccessible to all but the best breath-holders. While the habitat may be of lesser quality for foraging, it at least allows the fish to see another day. To see for myself, I plunged to 110 feet and was happy to find parrotfish cleaning turf algae off the reef and surgeonfish picking plankton out of the water, though all warily keeping their distance.

The Wildlife Conservation Society has been undertaking studies to investigate this depth refuge hypothesis. In 2009, our researchers conducted a series of surveys using stereo baited remote underwater video cameras (sBRUVs) on protected and unprotected reefs in the region. Placing bait with the camera rigs allowed us to see a much higher density of predatory fish than we would typically find using traditional SCUBA surveys and to investigate much deeper depths. What we have found is that outside protected areas, there are still considerably large populations of fish way down deep which are naturally protected by hiding out at depths which fishers cannot reach.

Scant fish life on the steep slopes (Photo: Keith Ellenbogen)

In order to bring the fish back to Mt. Mutiny and up from the depths, urgent management action is needed. However, the types of management required will have to set new precedents. Mt. Mutiny is unique among the NAI'A dive sites in that it is one of the few locations that falls outside of traditional fisheries management areas (qoliqolis). This excludes opportunities for customary management by communities. However, the national Protected Area Committee (on which I sit as an active member) is eager to investigate opportunities for offshore protection. A first step would be to ensure that fishing using any gear which targets deeper reefs is banned from the area. A second step would be to establish a strict nature reserve, targeting the unique seamounts scattered across Bligh Waters as a step towards World Heritage area listing.

My vision for the next 5 years is to energize conservation and management across this exceptionally rich seascape in Fiji so that next time I return the upper slopes of Mt. Mutiny will once again be teeming with fish life.

Stacy Jupiter, PhD

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