Lake Mead N.R.A.

Lake Mead N.R.A.

Friday, December 3, 2010

Restocking an Endangered Fish, The Bonytail Chub

December 3, 2010. Bill Williams River National Wildlife Refuge
Today, Joyce and I had the opportunity to work with some U.S. Fish and Wildlife Fisheries Biologists releasing endangered Bonytail Chub into the Colorado River and Lake Havasu.
Endangered Status The Bonytail Chub is on the U.S. Endangered Species List. It is classified as endangered throughout its range in Arizona, California, Colorado, Nevada, and Utah. This fish lives in large, fast-flowing waterways of the Colorado River system, and the large-scale damming of the river has diminished available habitat. Water-management practices such as damming and channeling not only change the speed, location, and volume of flow, they change the temperature and the clarity of the water and block migration routes. Other threats to the Bonytail Chub have been the introduction of non-native fish that compete for food and habitat, and may prey on it or hybridize with it.
The BonyTail Chub were released in two locatons. The first location was La Paz County Park on BLM land on the Colorado River south of Parker Dam.
Bonytail Chub Description To 24" (61 cm). Moderately elongate; greenish-gray above, sides lighter, whitish below. Breeding males reddish-orange below and on paired fins. Head short; snout depressed, broadly rounded, usually not overhanging upper lip; hump on nape in adults. Fins large, slightly falcate; usually 10 dorsal fin rays; 10-11 anal fin rays; caudal peduncle very narrow; caudal fin deeply forked. 75-88 lateral line scales; scales embedded or absent on predorsal area, belly, and caudal peduncle.
These Bonytail Chub were raised by the fisheries in various ponds before being released. They are released into the Colorado River systems once a year at this time. At this location 900 fish were released into the river.
The Bonytail Chub is so endangered that some biologists would argue that they are genetically extinct as they have not been able to establish that any Bonytail Chubs alive today have not been reproduced and raised in hatcheries. They do not seem to be successfully reproducing and thriving in their native environments.
Endangered species
Any species which is in danger of extinction throughout all or a significant portion of its range. Aspecies whose numbers are so small that the species is at risk of extinction.Where the populationof a species is dangerously low, so much that their gene pool diversity is adversely affected while there is a risk of the species being wiped out all together, usually a consequence from humangain.

All of the Bonytail Chubs that were released have an identification type chip (similar to pet chips) embedded in their body. However to track the Bonytail Chub movements in the rivers and lakes some of those that are released have a tracking sensor surgically placed in their body. Here near the shore at our refuge, biologists were inserting the sensors in the abdomen of 20 select Bonytail Chub.

The Bonytail Chub are first anesthetized in a water solution.

The capsule shaped sensor below is inserted in a select Bonytail Chub.
It's not every day that I get to hold the most endangered fish in the Colorado River! Intentionally killing or molesting this fish could result in a $10K fine. This one has been anesthetized for surgery to implant the sensor above.
A large truck from the hatchery carrying 2100 Bonytail Chub arrived at our refuge to release it's cargo into Lake Havasu.
The fisheries personnel were sure to match the water temperatures of the holding tanks with the lake. In this case the water was about 57 degrees.
Not exactly a graceful exit!
Both the Razorback Sucker and the Bonytail Chub have trouble competing against introduced species in an environment in the Colorado river that has changed from a warm flowing turbulent river to a series of cool calm lakes. To protect these endangered species, water releases from dams are regulated to protect spawning areas. Ambitious stocking and habitat improvement programs as well as intense scientific study are aimed at restoring self sustaining populations wherever possible within their natural environment.
We enjoyed our opportunity to participate in this important attempt at saving the Bonytail Chub from extinction.

1 comment:

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