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The Tonga Trench Project

The Tonga Trench Project base is in 'Eua, a small island belonging to the Tongatapu group in the south of Tonga.

There are 23 whale and dolphin species supposed to occur in the Tongan waters. One of the most famous and best researched is the humpback whale. But what makes 'Eua a special place for the Tonga Trench Project and cetacean research is it's vicinity to the Tonga Trench.

The Tonga Trench is the world's second deepest under water canyon. It reaches a depth of 10882m. Only the Mariana Trench is deeper. Therefore the seafloor off 'Eua drops down very steeply. Few hundred meters off the coast the water is already about 3000m deep.

For this reason not only the humpback whales but also very little researched offshore whale and dolphin species occur close to the shore. These are for example sei whales, fin whales, rough toothed dolphins and melon-headed whales which usually stay far away from land. That makes it really difficult to study them. You probably have never heard their names but you can learn about them on our web pages.

There are also the more famous bottlenose dolphins, spinner dolphins and sperm whales which are regularly observed around 'Eua.

What We Study

->migration patterns of the whales and dolphins in the Tongan waters:
Which species migrate seasonally between feeding and calving grounds? Which species migrate daily between inshore and offshore waters and which species do not migrate at all? link to side: migration coming soon

->vocalizations of the whales:
Which species produce which sounds and how many animals of one species produce how many sounds? This lays the foundation for an acoustical census of the whales and dolphins which is cheaper and more efficient than a visual survey since cetaceans spend about 95% of their life under water. link to side: vocalizations coming soon.

-> behavior:
What behavior are shown by the whales and dolphins in the Tongan waters? Do they feed? Do they travel? Do they mate or give birth? This gives us information about how the cetaceans use their habitat and therefore how important the Tongan waters are for them. How sensitive are whales and dolphins to changes in this environment. link to side: behavior coming soon

-> fishery interactions:
Which threats caused by the fishery do the whales and dolphins in the Tongan waters face and which solutions can be found together with the fishermen, to minimize these threats? link to side: threats coming soon..

Latest update on the Tonga Trench Project

Tonga Trench Project History

Home Page,

Whale Species,

Dolphins Species,

The Different Porpoise Species

Biology of whales

Anatomy of Whales