Wahweap State Fish Hatchery Breeds Woundfin for First Release in Virgin River

DWR Biologists Release Woundfin into Virgin River 3/10/11 | Photo by Joyce Kuzmanic

HURRICANE – Woundfin (Plagopterus argentissimus) is a small minnow historically native to two tributaries of the lower Colorado River Basin, including the Southern Utah’s Virgin River and parts of the Gila River.  Currently, the woundfin are only found in the Virgin River, ranging from Pah Tempe to Lake Mead, due to a declining population.

In 1970, the United States Fish & Wildlife Service listed the Woundfin as an endangered species.

Utah’s Division of Wildlife Resources has been collecting wild woundfin since the 1990s for brood stock at its Wahweap State Fish Hatchery, Utah’s only warm-water fish hatchery, established in 1972.

Zane Olsen and Travis Dees, who man the Wahweap Hatchery, arrived in Hurricane yesterday around noon with woundfin to be stocked into the Virgin River.

DWR’s Native Aquatic Biologist Melinda Bennion and Biologist Brooke Cox met up with Olsen and Dees, and a team of biologists from the DWR.

As the woundfin are transferred into coolers for transport to the release locations, the enthusiasm is contagious.  Cameras are flashing, hands are gently picking up the fish, and squeals exclaim,” They’re beautiful!” “Oh!  A fat one!” “These are so awesome!” And more.

Olsen illuminates: “This is the first year the Wahweap Hatchery has had enough natural offspring of the woundfin to both maintain the brood stock and take some to stock the river.”

“It takes years to develop the brood stock; we make sure the genetics are diverse, generally the more diverse genetically, the more adaptable the fish.”

Approximately 1,078 woundfin hatched in June 2010, were suitably grown to contribute to the DWR’s population recovery effort, helping to replenish woundfin in the river this year. Of these, 20 underwent necropsies before the balance were released.

“Necropsies are standard to make sure that the fish are healthy and not containing any viruses or bacteria that would contaminate the ecosystem,” Olsen said.

Since 2003, Utah’s DWR “has stocked over 59,000 woundfin,” Bennion said. “ These were successfully spawned in the Dexter National Fish Hatchery in New Mexico.  Of those, 57,000 were released into the Virgin River and about 2,000 into off-channel refuge ponds.”

“This sounds like a lot,” Bennion said, acknowledging, “ but the woundfin’s lifespan is only 1 to 2 years;” Olsen interjected clarification: “in its natural river habitat; woundfin can live three and even four years in the less threatening environment of the hatcheries.”

But given the short lifespan in the natural setting, Bennion stressed, “we have to continually restock until we have a viable population that is self-sustaining.”

In furtherance of the recovery plan, Wednesday’s restocking for the first time from Utah’s own Wahweap Hatchery is very exciting.

The process of identification, release and tracking is methodical.

First, each of the woundfin is hand-tattooed with a visual implant elastomer, or VIE, a little line of fluorescent color injected under the skin.  Each hatchery has its own color, Wahweap’s is orange, and the VIE is placed to the right of the dorsal fin on fish released in the spring, to the left on fish released in the fall.

Because the woundfin have no scales, Bennion said these VIEs are easy to spot as the DWR biologists periodically seine the river for samples, identifying, counting and measuring the fish to assess the progress of the recovery plan and the success of each release.

“Yes, we actually collect them in nets and count them one by one,” Bennion said laughing.

Next, the fish are divided for release points. In this case, allowing for a slight mortality factor, just over 300 were designated for release below the Hurricane Bridge, and over 700 were designated for release in what the DWR calls the “Above Quail Lake” section, adjacent to the Interstate Rock gravel pit.

The biologists have only joy and no complaints at the tedious process acclimating the fish for release.  Olsen bursts into laughter at the irony of his excitement:  “I’m excited over a tiny woundfin,” one exceeding 2 inches in length, as he remembers his earlier years when he exulted over catching a 2-foot trout. “The bigger the fish, the more the eggs!” he cried.

Adding river water to the transport water in portions every five to 10 minutes – both to balance the temperatures and to introduce the woundfin to the river water composition – the fish are ready for release when the comparative temperatures are within 1 degree of each other.

The biologists then individually sample measure the first 100 fish to be released, tossing them into the river one by one.  The remainder are counted and introduced to the river, again one by one.

The biggest threats to the woundfin currently are summertime lower water flows and rising river temperatures, as well as the nonnative red shiner which DWR is working diligently to eradicate.

DWR expects to do a second spring stocking of woundfin this May, from woundfin bred in the Dexter Hatchery.

As Olsen and Dees headed out for the two-and-a-half-hour return trip to Big Water (Wahweap), they expressed satisfaction with this accomplishment which has taken years to culminate.

Asked what’s up next of note for from the Wahweap Hatchery, Olsen announced, “Twenty-six thousand bonytail chub to be released into the Colorado River in November.”

Read more: Fish flourish from Dixie floods

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Copyright St. George News, SaintGeorgeUtah.com LLC, 2011, all rights reserved.



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