Lit­tle cleaner wrasses of­fer spa ex­pe­ri­ence to other fish

Honolulu Star-Advertiser - - LOCAL - SU­SAN SCOTT Reach Su­san Scott at su­sanscott.net.

Last week, in about 7 feet of wa­ter, I swam over a reef wall and found my­self in the mid­dle of a dozen jacks, a new species to me, each bear­ing yel­low, dash-like marks on their sides.

Hav­ing a mon­ster in their midst caused the fish to dart up, down and around, but sur­pris­ingly they didn’t flee. When I backed off, I saw why. The jacks were wait­ing for a turn at the spa.

Reef spas are run by nar­row, 4-inch-long fish called cleaner wrasses. A va­ri­ety of fish pick good­ies off other fish for food, but only the cleaner wrasse sets up a ser­vice sta­tion. It’s a on­estop shop for pest re­moval, wound de­bride­ment and mas­sage.

The wrasses work alone, in pairs or in teams up to five. To ad­ver­tise their busi­ness, the lit­tle fish bob their neon-like bod­ies up and down. The front half of the fish’s body is a glow­ing yel­low, and the rear half is pur­ple with laven­der edges. A black stripe runs from eye to tail, ac­cen­tu­at­ing the fish’s bright col­ors.

You can’t tell a male from a fe­male cleaner wrasse by color, but you can tell a ju­ve­nile from an adult be­cause young clean­ers are nearly all black. The kids get their grown-up col­ors early on, when they’re only about an inch and a half long. If a cranky adult chases away a lit­tle wrasse sport­ing its new col­ors, the young­ster can change back to black and safely move to a friend­lier neigh­bor­hood.

When I first learned about cleaner wrasses while study­ing bi­ol­ogy at the Univer­sity of Hawaii, the fact that Hawaii hosts an en­demic species was so em­pha­sized that I thought the lit­tle ser­vice fish was a Hawaii-only phe­nom­e­non. Later, though, I saw sim­i­lar cleaner wrasses on just about ev­ery reef I vis­ited in the trop­i­cal Pa­cific. The Hawai­ian cleaner wrasse, it turns out, is only one of five species in the In­dian and Pa­cific oceans. Ours, though, is the pret­ti­est.

Not all fish that visit wrasse clean­ing sta­tions have par­a­sites or dead skin that’s bug­ging them. Re­searchers be­lieve that the sen­sa­tion of the wrasses’ fins wig­gling against the skin feels good to their clients. Big fish some­times come just for a back rub.

The jacks I saw lin­ing up for a rub­down are a rather rare species here. Called is­land jacks, yel­lowspot trevally or ulua, these sil­very fish with yel­low side spots usu­ally school in deep wa­ter but some­times come in­shore. They grow to about 28 inches.

I’d never be­fore seen a school of is­land jacks or watched any jack hold per­fectly still with mouth and gill cov­ers open while a cleaner wrasse worked it over. That’s why I don’t mind snor­kel­ing in the same seem­ingly un­re­mark­able places over and over. I never know what I’m go­ing to get, and it’s al­ways an ad­ven­ture.

COUR­TESY SU­SAN SCOTT

A cleaner wrass with an is­land jack cus­tomer.

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