Category Archives: In The Water

Crown-of-thorns sea star and its nemesis

crown of thorns

giant triton snailCrown-of-thorns sea stars (Acanthaster planci) feed on coral and, because of this, are considered a menace to the health of coral reefs. Up to a foot-and-a-half across, they can have as many as 19 arms and are covered by venomous spines. If this all sounds like this creature is a nasty piece of work, the good news is that it has not caused extensive damage to the reefs here in Hawaii.

The crown-of-thorns does have predators, one of which is triton’s trumpet (Charonia tritonis). These large triton snails, up to 20 inches long, feed on echinoderms including crown-of-thorns sea stars. When they scent prey, they will take off after it and are considered speedy for a snail. When a triton’s trumpet catches its prey, it grips it with its foot and applies saliva that causes paralysis, which allows the snail to consume its meal without further drama.

Pearly soldierfish

pearly soldierfish

pearly soldierfish individualSoldierfishes are nighttime plankton feeders. By day, most rest in sheltered spots such as under ledges, in caves, or in deep holes in the rocks. Pearly soldierfishes area little different in that, during the day, they rest in the open just above the reef.

Like all soldierfish, the pearly soldierfish is notable for its large eyes and reddish coloration, though usually with the pearly sheen that gives it its name.

Redbarred hawkfish

redbarred hawkfish

Redbarred hawkfish, like other hawkfish, spend most of their time perched motionless on a rock or coral head, waiting to dart out at passing prey, usually little fish or small crustaceans. On some fish, the bars are more of a brick red, similar to the color of the red pencil urchin on the left of the photo.

Green turtle feeding

Green turtle and tidepool

Green turtle feedingGreen turtle feedsToward the end of a hike along the coast, I came across this turtle feeding in a shallow tidal area. There was good grazing to be had, but the problem was that the ledge was continually swept by incoming waves.

The turtle would swim in and access the ledge from the shore side (on the right in the top photo). Then he lumped forward to where the good grazing was and buried his head in it.

Waves would surge in and sluice over him (below). Sometimes, the receding wave had enough oomph that it would wash the turtle over the front edge of the ledge. Then he’d swim around and start over again.

Green turtle surge

Big-eye emperor

Big-Eye Emperor

This big-eye emperor fish gave me the big eye, which is very unusual. Big-eye emperors are the kings of hanging in the water and imperceptibly drifting away. It’s an act of extreme futility to try and get close. The more you try, the farther away they get.

Kawaihae dirt storm

Kawaihae dirt storm

The winds were blowing here last week, 30+ mph on a consistent basis. But one afternoon the winds picked up even more and triggered dirt storms off the hills above Kawaihae.

The wind whistled down the slope from Kohala Mountain and dry dirt was gathered up, whirled around, and blasted down the slope toward the ocean. This happened for an hour or so. Sometimes, white sand from the beach in Kawaihae harbor was similarly stirred up.

The unfortunate aspect of this display was that it visibly demonstrated the problems with erosion when the ground is dry. If it’s not the wind, then any rainfall washes the soil down gullies and into the ocean. All this dirt being deposited in the relatively shallow waters off the coast degrades the water quality and can have a seriously adverse effect on corals in the area.