Crawdads colonize the West's waterways

Down South, they call them 'Cajun popcorn.' In the West, they're a menace.

  • Virile crayfish devastating some Ariz. streams

    Philip Fernandez/Grand Canyon Univ.
  • Biologist Mike Demlong and son, Andrew, check for crayfish

    Guy Webster photo
 

MESQUITE WASH, Ariz. - On a spring-like Sunday afternoon, Mike Demlong, a biologist with the Arizona Game and Fish Department, and his 9-year-old son, Andrew, pick their way up a desert wash northeast of Phoenix, Ariz. Despite the dry winter, a stream trickles through Mesquite Wash, between its scrubby namesake trees and a few stouter cottonwoods.

From time to time, father and son crouch and peer at the bottom of a clear pool. Most are studded with black snails, but Demlong isn't looking for snails. He's in search of an armored predator that is wreaking havoc on Arizona's streams. In New Orleans, they call these crustaceans "Cajun popcorn." Demlong calls them crayfish; they're also known as crawdads or spiny lobsters.

Arizona has no native crayfish. But for decades, government agencies have released them into the state's waters to control weeds and to feed bass and other game fish.

Fishermen, who use crayfish for bait, have also helped the creatures spread. Once established, crayfish don't just feed the fish - they feed on fish, and on just about anything else they can get their pincers around.

"This gives a little idea what they can do," says Demlong, pointing to a six-foot-wide pool where the gravel bottom is bare of snails. Several other types of creek life, from algae to insects, are also noticeably sparser than in other pools.

Mesquite Wash has gotten off relatively easily. In other Arizona streams, researchers have documented declines in turtles, frogs and fish after non-native crayfish show up. "They're devastating aquatic ecosystems throughout the state," says Demlong.

This spring, Demlong is preparing a proposal to ban selling or transporting live crayfish in the state. Around the West, fish and game departments are waking up to the dangers of spreading these non-natives, though for many streams it could be too late.

A ravenous newcomer

Few understand the dangers of non-native crayfish better than biologist Philip Fernandez of Grand Canyon University, a private college in Phoenix. "I used to like eating them," he says, "but now I think of them as aquatic cockroaches."

He has watched a four-inch-long crayfish drown and completely consume a 10-inch garter snake. "You know those machines used for chipping branches?" he says. "That's what their mouths are like."

Fernandez has been studying wildlife in one small, unnamed stream in eastern Arizona's White Mountains for 13 years. He first found crayfish here seven years ago, apparently after some angler's well-meaning release of live bait. The changes he has witnessed since then are startling.

"They have transformed a clear, biologically diverse stream into a muddy stream that just has thousands of crayfish in it," says Fernandez. "First they eat the vegetation. There's not a scrap of vegetation left. They eat the pond snails, the mayfly larvae, caddisfly larvae, other insects. Then they go after the vertebrates. They eat tadpoles, fish, turtles, garter snakes."

Even the stream's brown trout have disappeared. Trout can eat small crayfish, but not larger ones, which devour the fishes' food supplies. The local population of Chiricahua leopard frogs may be doomed, too. The frogs have survived only in one pool, which the crayfish hadn't reached. But in the past year, crayfish have appeared here, too.

Fernandez and 10 helpers pulled more than 2,000 crayfish out of a short stretch of the stream one morning last summer, but missed others that had burrowed out of reach.

Scrambling for solutions

The problem is neither new nor limited to Arizona. Every other Western state has at least one native crayfish. It is the non-native crayfish that are causing problems.

In Nevada, the non-native Louisiana red swamp crayfish has nearly wiped out one of the three remaining populations of the endangered Pahrump poolfish. The poolfish go dormant in winter, making them easy prey, says Jon Sjoberg, a biologist with the Nevada Division of Wildlife. Sjoberg is also concerned about how the recent spread of crayfish to the Beatty area will affect the Amargosa toad, unique to that area.

In Northern California, the non-native signal crayfish is displacing the native Shasta crayfish, an endangered species. "We've been trying to remove the signals, but it's difficult to get all of them," says biologist Rebecca Miller with the California Department of Fish and Game.

Both Nevada and Utah forbid moving live crayfish from one water to another within the state. Other states, including California and Montana, may soon follow suit.

Montana biologists worry that imported crayfish could spread disease to the state's three native crayfish species. The state is already struggling to cope with the effects of the non-native parasite that's causing whirling disease in trout (HCN, 9/18/95: Tje West's fisheries spin out of control).

Montana allows residents to import live crayfish only for keeping as aquarium pets. Now, state fisheries officials are drafting a proposal to close that loophole, to be presented to the Montana Fish, Wildlife and Parks Commission later this year.

Montana biologist Jim Peterson says, "We're learning from experience that we need to be careful about introducing any exotic species, whether it's crayfish or anything else."

The author writes for the East Valley Tribune in Mesa, Arizona.

YOU CAN CONTACT...

  • Mike Demlong, Non-game Division, Arizona Game and Fish Department, 2221 W. Greenway Road, Phoenix, AZ 85023 (602/789- 3504); [email protected];
  • Philip Fernandez, Biology Department, Grand Canyon University, 3300 W. Camelback Road, Phoenix, AZ 85017 (602/789-3504);
  • Jim Peterson, Fisheries Division, Montana Fish, Wildlife and Parks, 4801 Giant Springs Road, Great Falls, MT 59405 (406/452-6181).

Copyright © 2000 HCN and Guy Webster

High Country News Classifieds
  • GENERAL MANAGER
    The Board of UYWCD seeks a new GM to manage operations & to implement our robust strategic plan. Details at www.upperyampawater.com. EOE
  • IN TUCSON, FOR SALE: A BEAUTIFUL, CLASSIC MID-CENTURY MODERN HOME
    designed by architect David Swanson in 1966. Located a block from Saguaro National Forest, yet minutes to Downtown and the UofA campus, 3706 sqft, 6...
  • EXECUTIVE DIRECTOR
    The Friends of the San Juans is seeking a new leader guide our efforts to protect and restore the San Juan Islands and the Salish...
  • 80 ACRES
    straddles North Platte Fishery, Wyoming. Legal access 2 miles off 1-80. Call 720-440-7633.
  • DIRECTOR OF PRODUCT AND MARKETING
    High Country News seeks a Director of Product and Marketing to join our senior team during an exciting chapter of innovation and growth. This individual...
  • OWN A THRIVING MOUNTAIN GUIDE SERVICE.
    Eastern Sierra guide service for sale to person with vision & expertise to take it onwards. Since 1995 with USFS & NPS permits. Ideal for...
  • IMPROVED LOT
    Private road, hillside, views. Well, pad, septic, 99 sq.ft. hut. Dryland permaculture orchard. Wildlife. San Diego--long growing season
  • UNIQUE INVESTMENT OPPORTUNITY
    Profitable off-the-grid business located 2 miles from Glacier National Park. Owner has 6 years operating experience. Seeking investor or partner for business expansion and enhancement....
  • REMOTE SITKA ALASKA FLOAT HOUSE VACATION RENTAL
    Vacation rental located in calm protected waters 8 miles from Sitka, AK via boat with opportunities to fish and view wildlife. Skiff rental also available.
  • EXPERT LAND STEWART
    Available for site conservator, property manager. View resume at http://skills.ojadigital.net.
  • CONSERVATIONIST? IRRIGABLE LAND?
    Stellar seed-saving NGO is available to serious partner. Package must include financial support. Details: http://seeds.ojaidigital.net.
  • CANYONLANDS FIELD INSTITUTE
    Colorado Plateau Natural & Human History Field Seminars. Lodge, river, hiking options. Small groups, guest experts.
  • WESTERN NATIVE SEED
    Specializing in native seeds and seed mixes for western states.
  • CHUCK BURR'S CULTUREQUAKE.COM BLOG
    Change will happen when we see a new way of living. Thinking to save the world.
  • COMING TO TUCSON?
    Popular vacation house, furnished, 2 bed/1 bath, yard, dog-friendly. Lee at [email protected] or 520-791-9246.
  • OJO CALIENTE COMMERCIAL VENTURE
    Outstanding location near the world famous Ojo Caliente Mineral Spring Resort. Classic adobe Mercantile complete w/living quarters, separate 6 unit B&B, metal building and spacious...