Juvenile threadfin jack

Juvenile Threadfin Jack

Threadfin Jack Juvenile


This little diamond-shaped fish is probably my favorite to see on the reef. The first time I saw one I thought it was a jellyfish, shimmering along with its long filaments wavering behind it. I got a little closer and realized it was actually an extraordinary fish.

The juvenile gives no hint of what it will look like as an adult. It grows to four feet in length, becomes stocky, loses the filaments entirely, and ends up looking like a nightclub bouncer.

It’s always a thrill to see one of these, its little tail thrashing back and forth, hauling the long filaments behind it as it putters through the water.

In my attempts to identify what I see in the water, I use John P. Hoover’s book The Ultimate Guide to Hawaiian Reef Fishes, Sea Turtles, Dolphins, Whales, and Seals. His website is hawaiisfishes.com.