Nunu the Hawaiian trumpet fish grows over 24 inches long, but it is only about 3 inches thick. They are also known as stick fish, as they just look like a long stick swimming underwater. Nunu look harmless as they have a tiny mouth and they swim slowly, sometimes standing on their head. They come in many different colors from green, brown, striped, banded to bright yellow.
What makes nunu unique is the way they hunt for small fish. If you look sideways at the nunu, it looks like a big fish. But if you look directly at its face head on, it only looks like a small fish.
The trumpet fish is built like a vacuum cleaner hose and its long small mouth can expand several times its normal size. When nunu gets close to a small unwary fish, it opens its mouth super fast and sucks in the small fish for a meal.
The problem is the nunu is such a large fish the small fish can see it coming and they hide in the reef so nunu has developed a very sneaky way of hunting.
Large schools of algae eating fish, like the convict tang and surgeonfish move all over the reef feeding on the limu (seaweed) growing on the reef. These schools can consist of more than 100 fish and they over power smaller algae eating fish by their sheer numbers.
Small algae eating damselfish are territorial and they protect their small algae farms for their own food, and the big schools of tangs are their enemy. The damselfish can be very aggressive protecting their turf, so the school of tangs has developed a way to get rid of the small aggressive fish.
Large, 30-inch long nunus will swim right in the middle of a school of 100 tangs, so they can’t be seen by the small reef fish. When the tangs feed on algae the aggressive damselfish attacks the tangs trying to protect their part of the reef, and the nunu sucks them right into their mouth.
The small fish never saw the big predator nunu hiding right in the middle of the tang school.
The nunu gets to feed on the attacking small fish and this makes it easier for the school to feed without being molested by the aggressive damselfish. It gives new meaning to the saying ” speak softly but carry a big stick.”
The large school of tangs comes armed with a fierce predator right in the middle of their school. This works so well for the tangs and nunu that the trumpet fish will change colors to match the species of tangs it is hunting with. A green banded nunu will hunt with a school of banded convict tangs and a yellow nunu will hunt with a school of yellow tangs.
On land, this type of cooperative hunting would be like a flock of sheep hiding a wolf right in the middle of the sheep, so a rabbit would get eaten by the wolf giving more grass for the sheep to eat. Just bring along a predator to eat your competitors for the type of food you eat.
You can see the nunu in action cruising around with a huge school of manini (convict tangs) in my documentary movie about marine life at Koloa Landing in Kaua‘i that is posted on my underwater educational webpage at www.underwater2web.com.
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Terry Lilley is a marine biologist living in Hanalei Kaua‘i and co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawaii go to www.reefguardianshawaii.org.
