Tag Archives: Opae ula

Opae ula are hardy critters, but treat them with respect

Published October 1, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser
©2016 Susan Scott

If you dig it, they will come. Not the ghosts of baseball past, but equally enchanting, the shrimp of Hawaii present: opae ula.

Also called anchialine (AN-key-ah-lin) shrimp, opae ula are half-inch-long creatures that live in underground cracks and pukas containing a mixture of fresh and sea water

When a nearshore opening, natural or human dug, appears above the shrimp’s tunnels and forms a pool, the creatures emerge from below, eat whatever is available and multiply. Mostly the shrimp live on algae that grows on their rocks, but they also eat dead insects that fall into their pools and bacteria that grow in their water.

The hardy shrimp tolerate variable degrees of salinity and can live up to 20 years with little care. The little crustaceans are usually red but can be pink, orange, yellow, white or clear. DNA studies today show that Hawaii’s opae ula consist of at least eight genetically different populations.

p1030957I’ve written about anchialine shrimp before but information about the charming native creatures and their pools was hard to find. No more. Now we can read facts about our opae ula in a $13.95 paperback titled “Hawaiian Anchialine Pools, Windows to a Hidden World” (Mutual Publishing, 2015).

The book contains just about everything everyone knows about our little shrimp, including references for those who want more details. Clearly written by Hawaii researchers — Mike Yamamoto, Thomas Iwai and Annette Tagawa — the book also has great photos.

Most people don’t see these remarkable shrimp in pools, but rather in jars, vases and other clear containers sold in Hawaii shops and online. As for buying the shrimp, the authors don’t advocate it but acknowledge that opae ula make fascinating pets and are for sale locally and on the internet.

It’s researchers’ hope that keeping opae ula at home or the office raises awareness of the importance of preserving Hawaii’s anchialine pools. Due to coastline development and thoughtless people tossing trash and fish into these special bodies of water, Hawaii’s anchialine pools and their famous native inhabitants have dwindled in number.

If you decide to host some opae ula, buy them. Collecting your own is prohibited. When buying, confirm that the shrimp have either been raised through aquaculture or come from a state permit holder with permission to collect in a particular pool.

Of the 700 or so anchialine pools left today, about 650 are on the Big Island. Maui and Oahu have a few, some listed in the book. At least one business and one research team I know have created anchialine pools by digging holes in porous seaside rock. And as if by magic, the shrimp appeared.

When you visit a Hawaii pool of dreams, prepare to be awed.

Anchialine shrimp thrive in a troubled environment

Published February 3, 2014 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2014 Susan Scott

Last week I attended a talk given by a federal biologist who, before her funding was cut, worked with Hawaii’s anchialine shrimp, known as opae ula. Although these shrimp inspire nearly endless questions, I had a specific one in mind: Is it OK for a conservation-minded person to buy anchialine shrimp, sold in jars at Shi­ro­kiya and also online?

“Anchialine” (AN-key-ah-lin) is a Greek term meaning near the sea, and describes pools with indirect connections to the ocean. The coastal pools are found in limestone and lava deposits where fresh water and seawater both percolate through the porous rock.

The salt content of anchialine pools varies from pool to pool and from top to bottom. Most pools fluctuate with the tides, but the water doesn’t always mix. Often the deepest part of a pool contains seawater, the middle is brackish and the top is fresh.

At least seven aquatic species thrive in Hawaii’s anchialine pools. Some found in Hawaii are also found in pools of Egypt and Japan, but Hawaii’s most famous inhabitant is the endemic opae ula, the Methuselah of shrimp. Most live from one to six years. No one knows how long the half-inch opae ula can live, but some are still going strong after 20 years in captivity.

Opae ula can also live in fresh to supersalty water and tolerate a 20-degree water temperature change.

Opae ula are “Field of Dreams” creatures in that if you dig it, they will come. Individuals somehow survive for decades in aquatic underground cracks and crevices. But if someone digs a hole above their caves to the surface and cleans all soil and clay from the pores, up come the shrimp.

Life in the sun is grand, with food growing on rocks. With ample algae and bacteria to graze on, the shrimp thrive and multiply.

Oahu, Maui, Kahoolawe and Hawaii island all have anchialine pools containing opae ula. Most are hard to find or visit, but a couple on Hawaii island are easy. Owners of the Kona sea horse farm, Ocean Rider, dug their own pool, and it’s so loaded with opae ula that managers feed the shrimp to their baby sea horses. The Four Seasons Resort at Hualalai also has attractive pools, black lava speckled in bright red.

So. Should admirers of opae ula buy them?

No, the biologist told me. Although the shrimp aren’t officially listed as endangered, their habitat is in trouble. Alien fish introduced to the few remaining anchialine pools eat the shrimp, and hole-filling for development destroys their homes. Also, she said, the shrimp don’t do as well as advertised in those closed ecosystems.

But the government program that enabled this biologist to study the shrimp and restore several of Oahu’s anchialine pools was eliminated by budget cuts. Perhaps by sharing details about their special pets, informed opae ula owners help inspire support to fund studies and protect pools.

To buy or not to buy is just one more opae ula unknown. But one thing I do know. Whether gazing at these creatures in a glass jar, an open aquarium or an anchialine pool, the tiny red crustaceans give a person a lot to think about.


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2014 Susan Scott