Ocean Watch

I found Nemo.

And his mother, father, sisters, brothers, aunts, uncles and all his distant cousins. Almost everywhere I snorkel here in Tonga, I find little orange Nemos, or clownfish.

But it doesn't matter how abundant they are. I still nearly always stop to watch them.

OK, tease them. Clownfish, also called anemonefish, are so territorial that if a creature gets anywhere near their anemone home, they dash out to fight the intruder.

And it's no show. This week, I drew close to a large shallow anemone sheltering two particularly energetic clownfish. Both of those 6-inch-long fish charged me, even baring their tiny white teeth as they darted toward my mask.

I backed off and the two fish returned -- smugly, I imagined -- to the protective tentacles of their stinging abode.

Hawaii hosts no clownfish, and our anemones are tiny and few. But here in the South Pacific, the orange striped fish and their symbiotic pals are common. The anemones protect the clownfish from fish predators that can't tolerate stings; the clownfish protect the anemones from their main predators, butterflyfish.

Some anemones are only the size of a saucer with short bubble-shaped tentacles. Others are as big as throw rugs with long, wormlike tentacles.

These jellyfish relatives live wherever they find a good spot to hang on, a nook in a rock or the crack of a coral head. Anemones usually stay in one place, but occasionally one will slide on its broad base from one place to another, flying carpets in slow motion.

Some clownfish anemones live more than 100 years.

Anemones multiply by releasing fragments of themselves or by discharging eggs and sperm (the sexes are separate) into the water. In both cases, reproductive success is low, often the case in long-lived animals.

Clownfish are not born immune to anemone stings. An uninitiated clownfish approaches an anemone and brushes belly or tail against the tentacles. The fish gets stung and darts away but returns repeatedly. Gradually (hours or days depending on the species) the fish can safely engulf itself among the tentacles.

One theory explaining this acquired immunity is that the anemone's mucus coats the fish, and the anemone can't then distinguish the fish from itself. Another theory suggests the fish's mucus coating changes the anemone's stinging cells so they don't fire.

However it works, clownfish earn their safe homes.

The female lays eggs next to her anemone's base, and the male keeps them clean by fin fanning. Both sexes vigorously defend their nest and their host.

Last week, I mentioned to an American resort owner here that I enjoyed finding Nemos all over the place. He laughed.

"That movie has done more for marine life than anything else ever has," he said. "When I tell kids who are afraid of the ocean that Nemo is here, they can't get in the water fast enough."

It's not just kids who love that movie. Finding a zillion Nemos has been a highlight of my visit to Tonga.