Restocking rare fishes

James E. Johnson (jjohnson at comp.uark.edu)
Mon, 22 Jan 1996 09:25:53 -0600 (CST)

Concerning the question of whether to return native fish to their
historic habitats after being cultured in hatcheries, I can tell you the
policy we used at Dexter National Fish Hatchery. We tried never to move
native rare fish into culture out of a wild population and then move
hatchery produced fish back into that same wild population or habitat. The
reason for that policy was the slight possibility of introducing disease
organisms or parasites from the hatchery into the wild population. Also,
once several generations were produced in the hatchery, there is a chance
that the genetic bottleneck created there might affect the wild
population.

We have stocked rare fishes reared in hatcheries into "likely" historic
habitats
if the wild population has been extirpated and it seems reasonable to
expect the habitat to allow the fishes to survive and reproduce. We use
the term "likely" because historic collections are often spotty. It
seems "likely" that a habitat once supported a species if it was taken
historically within the drainage both above and below the "likely"
habitat. Species so stocked include razorback sucker (Xyrauchen
texanus), Colorado squawfish (Ptychocheilus lucius), Gila topminnow
(Poeciliopsis occidentalis), Big Bend gambusia (Gambusia gaigei), and
desert pupfish (Cyprinodon macularius).

If what appears to be suitable habitat exists above all of the historic
collections sites, then it is not as likely to have once supported the
species and will not be used for stocking. A case in point is the
Virgin River in Utah. Woundfin (Plagopterus argentissimus) and Virgin
chub (Gila seminuda) are both endangered and facing possible extinction
due to water demands on the Virgin River. Neither species was ever
collected above a very saline reach of the river (LaVerkin Spring) and
neither exist upstream of that point today, even though the habitat
certainly appears to meet all of the needs of both fishes. Neither the
woundfin or the chub will be introduced above LaVerkin Spring because it
is not likely historic habitat. If those species cannot survive in the
Virgin River within their historic reach, then they will disappear.
While this may seem a terrible choice, another endangered fish exists
above LaVerkin Spring, the Virgin spinedace (Lepidomeda mollispinis),
and introducing the two downstream fishes above LaVerkin Spring may lead
to the loss of all three.

James E. Johnson
jjohnson at comp.uark.edu
Arkansas Cooperative Research Unit
Department of Biological Sciences
University of Arkansas
Fayetteville, AR 72701
phone (501) 575-6709