You don't know jacks...

...but we do!

We know jacks (Family: Carangidae), and they are among our favorite kinds of fish. The family has many species, and everywhere in the world that we have dived we have encountered several species of jacks.

Diver with Bigeye Trevally (Caranx sexfasciatus)One species we've seen in numerous locations is the Bigeye Trevally (Caranx sexfasciatus). In fact we've seen these guys everywhere from the Red Sea, through the Indo-Pacific region, to Hawaii.

Bigeye Trevally - a.k.a. Bigeye Jacks - tend to gather in fairly large schools during the daylight hours. Usually they'll hang out with their gang along a dropoff or reef slope all day long.

Around dusk, they fan out into the open ocean to hunt all night as individuals. In the morning, they find their 'schoolmates' again and reconvene to spend the day near the same dropoff. Once they form up, they often swirl around in a dense pack -- a way for them to keep together and stay more or less in one place. It really is a sight to see.

Diver with Bigeye Trevally (Caranx sexfasciatus)Jerry likes to play with these jacks. In fact, what he likes to do is herd them. That's right, I said herd them! He discovered that he can approach a loose aggregation of these fish while they're still a bit offshore in the bottomless blue, and coax them to go more or less where he wants them to go by swimming alongside them, much like a cowboy would ride alongside a herd of cattle.

We had been diving along this particular dropoff very early in the morning for several days in a row. Each morning we had seen the jacks in more or less the same area. I was able to take quite a few shots of this very photogenic school of Bigeye Trevally, and while I was busy taking photos, Jerry was perfecting his herding skills.

I watched him for a little while and decided it would be fun to shoot a series of photos of Jerry-the-Jacks-Wrangler in action, demonstrating his fish herding skills. As you can see in the first two photos on this page, Jerry was able to herd the jacks from offshore to the edge of the reef and nudge them into a denser aggregation. These fish are ever-moving, of course, and eventually they would begin to swirl. When that happened, we'd swim out, away from the dropoff, and then look back just to watch them swirling. From that perspective it was quite a hypnotic sight.

On the morning this series of photos was taken, I had suggested ahead of time that after the jacks schooled and began swirling, Jerry try to get inside the swirl. I thought it would make an interesting photo.

Diver with Bigeye Trevally (Caranx sexfasciatus)Ever the cooperative model for my underwater photos, Jerry agreed to try to get inside the cyclone of Bigeye Trevally.

Diver with Bigeye Trevally (Caranx sexfasciatus)The fish kept swirling and swirling, and I kept on snapping the shutter, even though it was difficult to keep things in focus with all that motion. What an action sequence!

Diver with Bigeye Trevally (Caranx sexfasciatus)For his part, Jerry found that he could not remain stationary once he was inside the swirl. In fact, we eventually had to stop because Jerry was becoming quite dizzy!

Diver with Bigeye Trevally (Caranx sexfasciatus)I think the caption for this final photo in the sequence should be, "Can I stop now? Please???"

If these schooling jacks look somewhat familiar, it might be because they are also featured in the photo in the header of The Right Blue. The images were shot at Sipadan, an oceanic island in the Celebes Sea, off the coast of Borneo.


  1. aloha bobbie,
    as you know by now, i admire your tropical fish photos and your immense knowledge about all of them. i met the jacks at mauna lani fish ponds where they feed the fish + rays + baby sharks daily, including the jacks, to educate kids and parents about them. quite interesting experience. good way to get to know them when not being a scuba diver like you guys. poor jerry he must have been dizzy after all these swirls. amazing behavior though, the jacks, i mean. will be back for more fish stories. aloha, pua from best hawaii vacation

  2. Aloha Pua. Yes, the Mauna Lani fishponds on our island are interesting. As you say, they provide a nice opportunity for non-divers to see and learn things about the ocean's creatures.

    I think those jacks in the photos were just getting back at Jerry for herding them around. ;-}


  3. inside the swirl!!! beyond my imagination-

  4. Jerry had quite an experience - I bet not many others have done that - good thing you have the pics to prove it!

    The jacks are bigger that I thought they were - must be kind of spooky to have all those masses of fish - and they seemed to go on forever at varying depths.

    Too cool!


  5. @ Yuko (webmaster pomona) - Now we HAVE planted this scene in your imagination! ;-}

    @ Kathy - Some time after this experience, we tried the same thing with a swirling school of a species of barracuda, but it didn't work out so well. The barracuda spooked and scattered. These jacks were so much more cooperative!



We welcome your comments and invite your questions. Dialogue is a good thing!

Bobbie & Jerry