Ocean Watch

Recently, while sitting on the dock eating lunch at Kewalo Basin, reader Eric Sadoyama noticed an array of fish: tilapia, mamo (sergeant majors), manini (convict tangs), kihikihi (Moorish idols), boxfish, a baby kaku (barracuda) and some butterflyfish accompanied by a trumpetfish.
"But what really caught my eye," Eric writes, "was a school of eight or nine silvery fish ... with diamond-shaped bodies and beautiful long, trailing threads from their top and bottom fins. What were they?" he asks. "Are they native?"

Only in Hawaii can a person sit in the middle of the largest aquarium in the world and watch the marine world go by. I do it too in the neighboring Ala Wai Boat Harbor and often see the same fish. Only a few times, however, have I been lucky enough to spot the spectacular threadfin ulua (jack) or ulua kihikihi.

When I replied to Eric that those beautiful Hawaii natives are young threadfin ulua, he wrote back, "Aha, threadfin papio! One of my office mates hit it on the nose."

Threadfin papio, meaning juvenile ulua, is indeed the best name for these fish, because as they grow, their sparkling threads become shorter and shorter until they disappear.

At the same time, their bodies lose that distinct diamond shape. As adults, threadfin ulua look like most other ulua.

The scientific name of these striking fish is Alectis ciliaris. The species swims in tropical waters around the world, including the coasts of Africa. This explains the fish's official common name, African pompano.

A juvenile fish hauling around long, eye-catching fins seems to be asking for trouble, but the effect is the opposite. Since the fins resemble box jellyfish tentacles, researchers believe those flashy threads scare off predators.

Grown-up ulua don't need tricks to protect themselves. They just bully their way around the reef.

Last year while I lived and worked on Tern Island, a field station in the Hawaiian Islands National Wildlife Refuge, I came to know several ulua well. We guessed that some of the older ones swimming around the little island weighed up to 100 pounds. And those Goliaths weren't afraid of anything.

Jump in the water, open your eyes and a big black ulua might be staring you in the face. While scuba diving there, I once tried to push a pesky ulua away with my hand. The fish didn't quite let me touch it, but remained close to my side. The ulua there never tried to bite us; they were simply curious, fearless and always on the prowl for a meal.

During turtle season, these magnificent fish turned natural selection into a heartbreaking game. Each morning, one of us would scour the island for lost hatchlings. After collecting them in a bucket, we would lovingly set them on the sand near the waterline and let them swim naturally to sea.

With those ulua there, some turtles didn't get far.

Ulua are a favorite target of spear fishermen and are now scarce around the main islands. These fish are good to eat but have a major drawback: Members of this family feed on reef fish that can carry the poison called ciguatera.

Unless an ulua has been tested, eating one is risky. The best way to enjoy these fish is to take your lunch to a city dock, sit down and watch those beauties swim by.