Monthly Archives: April 2017

Snapping shrimp pop to send alert and nab food

Published April 15, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

Petroglyph shrimp channels are etched in lobe coral off Lanikai Beach. ©2017 Susan Scott

Decades ago, when Craig and I boarded a friend’s boat in the Ala Wai Boat Harbor, the crackling sound below deck made us wonder if the boat was falling apart. I later learned that the big noise comes from a small package: 1-inch-long snapping, or pistol, shrimp.

We oceangoers rarely see the little gunslingers because they live in burrows. But we hear them. The split-second closure of each shrimp’s single, oversize claw makes a popping sound. When the creatures pop by the thousands, as is often the case, it’s like snorkeling in a giant bowl of Rice Krispies.

The crackling is so loud that submarines can hide among shrimp colonies and go undetected by sonar.

The shrimp snaps for food, sending out a bubble bullet that stuns passing prey. The snaps can also be warning shots to trespassers, and perhaps a come-on to members of the opposite sex.

Most snapping shrimp dig, and live in, mud or sand burrows. We rarely see these basement apartments because they’re under rocks and rubble. One kind, though, lives in exposed sand burrows guarded by a pair of gobies. The shrimp digs while the fish keep watch. When a predator or curious snorkeler gets too close, the team dives into the hole together.

Other snappers, called petroglyph shrimp, set up housekeeping in living coral heads by making channels. No one knows how the shrimp creates the cracks. Either the animal is able to inhibit coral growth at the chosen site, or that big claw is an all-purpose tool that, in addition to firing lethal bubbles, can also dig.

Petroglyph shrimp (usually Alpheus deuteropus) create wavy, U-shaped crevices, the largest about a quarter-inch wide and 10 inches long. These are not the shrimps’ burrows, but rather boulevards lined with crops and cops.

The crops are seaweed, veggie meals for the shrimp. The cops are white hydroids, stinging jellyfish relatives that look like tiny trees. The hydroids protect the lane but might also eat the shrimps’ babies when they hatch. Security guards don’t come free. Gobies are carnivores, too.

The deepest parts of petroglyph channels bear cul-de-sacs that precisely fit each shrimp’s body. When it’s threatened, the shrimp retreats to its den, blocking the entrance with its large claw. Channels 2 inches or less usually house a single resident. Longer ones can accommodate two to four shrimp, each with its own separate burrow.

Hawaii’s petroglyph shrimp have pink eyes encircled by red dotted lines. The bodies are transparent with red surface dots.

So they say. I’ve not seen one. But I often see, and stop to admire, the shrimps’ plant-lined streets with twiggy sentries. The neighborhoods deserve a feature in Better Homes and Gardens.

Tetiaroa a fine spot for Obama to pen book

Published April 8, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

The Honu, bottom left, shared “The Brando” buoy with a catamaran at Tetiaroa atoll in 2015. @©2015 Susan Scott

The news that Barack Obama is writing his memoir in Tetiaroa caused excitement at our house. In 2013 we sailed the Honu 40 miles from Tahiti to Tetiaroa, when the luxury hotel hosting the former president was still under construction.

Tetiaroa, often called an island, is an atoll, consisting of a 4.5-mile-wide lagoon surrounded by 13 small islands, encircled by one huge coral reef. Onetahi Island houses the Brando Resort, so-named because Marlon Brando’s estate owns the atoll.

Because Tetiaroa’s reef has no channel, getting into the atoll’s lagoon by sailboat is impossible, and the sheer drop-off outside the reef is too deep for anchoring.

Arriving at the atoll off Rimatuu island, we saw a tourist catamaran tied to a giant, flat buoy labeled “The Brando.” The friendly Tahitian captain invited us to share the mooring, and soon the Honu was secure outside the break.

We weren’t sure how to get inside the reef, but our neighbor had a system. The skipper stood in a rubber dinghy steering the boat’s outboard with one hand and grasping the bow line with the other. His six passengers hung on, three to a side. Driving back and forth outside the break to time the breaking waves, the man seized his moment, opened the throttle and surfed into the lagoon.

Tetiaroa from above. By Supertoff – Own work, Creative Commons: BY-SA 3.0

After dropping his charges on the beach, the captain zoomed back toward the break, riding the mass of water rushing seaward. The collision of the outgoing water with the incoming wave launched the dinghy skyward. With a cigarette dangling from his mouth, this Polynesian Marlboro Man flew up and over the peak, and zoomed back to his boat for more guests.

After watching several of these astonishing performances, we decided to body-surf in. I lost a fin in the tumble, but Craig found it and off we went snorkeling.

Coral formations in that part of the lagoon had formed a kind of pond that hosted a large number of pipefish, relatives of sea horses. Somewhat rare, and usually alone or in pairs, the charming pipefish hung out in nearly every nook and cranny of that reef pocket.

Later, during my panicky exit through the surf, I again lost a fin. It seemed a price worth paying for snorkeling with packs of pipefish and surviving a dive through the washing machine wave.

When I got back to the Honu, my fin lay on the deck, found and delivered by the catamaran cowboy.

Tetiaroa Atoll is the perfect place for Hawaii-born-and-raised Barack Obama to write his memoir. For breaks he can snorkel with pipefish and body-surf the reef.

Map of Tetiaroa. Public Domain image.

A precious skeleton is found amid many birds

Published April 1, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

An aama molt is seen at Moomomi beach on Molokai. The shell of the Hawaiian black rock crab shows its true colors detached in the hot sun. The crustaceans molt their exoskeletons by separating skin from shell, then cracking a rear seam to exit from. ©2017 Susan Scott

While visiting Molokai last weekend, friends and I went to Moomomi Preserve, a 912-acre coastal area shaped by tradewinds so gusty they sandpapered our legs. It was worth the prickles.

Behind the beach stands a mile of dunes, wind-sculpted into bluffs of rippled sand. Since 1988, when the Nature Conservancy and the state’s DLNR began fencing Moomomi, several hundred wedge-tailed shearwaters have claimed the land above and behind the bluffs. Protected from predators, the seabirds dig their ground nests in peace, and the 22 native plants that grow there get their sandy soil aerated.

During our walk through this picture of ancient Hawaii, flocks of shorebirds called out over the roar of crashing waves, and turtles left behind their signature tracks.

Surprisingly, amid all this burrowing, booming and blowing, I found a fragile but intact remnant of a remarkable marine animal: the rock crab.

Hawaii’s rock crabs, also called aama, are the flat, black crabs we see hanging out on Hawaii’s basalt beaches and concrete breakwaters. When startled, the crabs skitter into cracks or jump into the water so fast you wonder what you really saw.

One Hawaii blogger calls our rock crab a “hot-rod decapod,” decapod meaning 10 legs.

Aama’s close relative is the well-named Sally Lightfoot crab, found on coasts in the eastern tropical Pacific. Sallys are easy to find because they’re bright red. Aama shells turn red, too, but never while they’re still wearing them.

Because crustaceans carry their skeletons on the outside of their skin, and those skeletons don’t expand, the creatures have to shed their shells to grow. The process resembles science fiction.

When it’s time to go up a size, the crab starts absorbing calcium carbonate from its old shell and begins secreting enzymes that separate skin from shell. The absorbing and secreting can take a few weeks.

On the big day the crab sucks seawater into its body and swells up like a balloon. This cracks the old shell along a rear seam, creating a backdoor exit. The crab pulls its body through the slit, taking its legs, eyestalks, antennae, mouth parts and gills with it.

As the crab recycles its absorbed calcium carbonate to make a new shell, it gradually replaces the inhaled seawater with protein.

When the sun hits the paper-thin molt left behind, the heat destroys the cells’ dark proteins. We then see the aama’s true colors: red and white.

We don’t see them for long. Sun and rain quickly break down the delicate molts, and soon they’re gone with the wind.

Finding a perfect, whole aama molt reminded me of the marvelous way our little hot-rod decapods grow.

Thank you, Nature Conservancy and state DLNR, for having the foresight to preserve and protect this extraordinary place.