9528 ‎(2)‎

• UCREFRP Catalog Number: 9528
• Author: Martinez, P. and N. P. Nibbelink.
• Title: Colorado Nonnative Fish Stocking Regulation Evaluation.
• USFW Year: 2004.
• USFW - Doc Type: Grand Junction, Laramie.
• Copyright Material: NO

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The index of threat is highest for green sunfish and largemouth bass. This is largely
driven by their prevalence because control measures for these species are about average
compared to other species (controls in 30-40% of ponds). White sucker, black bullhead,
common carp, bluegill, and black crappie all show a comparatively intermediate level of threat
after control, but as stated above, the effectiveness of control of each species depends entirely
upon which ponds are controlled. For example, although the overall threat posed by channel
catfish and western mosquitofish prior to control measures being applied is low compared to that
of other species, their level of threat changes minimally after control measures have been
implemented. This indicates that very few of the ponds known to contain these species were
subject to control measures, thus these ponds could potentially become future sources of channel
catfish and western mosquitofish. The potential threat of mosquitofish and channel catfish in
ponds reaching critical habitat would decrease further if control measures were applied to ponds
known to contain them, or possibly rise if it was learned that they exist in many more ponds than
is currently documented.
Pre- and Post-Regulation Fish Stocking_Data
From discussions with both private sector and CDOW personnel, it was determined that
ten in-state private aquaculturists were likely recent suppliers, from 1998 to 2000, of nonnative,
nonsalmonid fishes to Colorado's west slope. Additional inquiries internally indicated that three
to four of these vendors probably supplied 90% of the nonnative, nonsalmonid fish species sold
to private pond owners in western Colorado. Table 7 summarizes the response of the ten
vendors to written requests for voluntary submission of their stocking records for the years 1998-
2000. Only three vendors replied to this request for stocking data, with one vendor indicating
that they did not sell any nonnative, nonsalmonid fish species during 1998-2000. One vendor
provided stocking location information based on DeLorme's (1997) Colorado Atlas & Gazetteer
grid coordinates. Another vendor provided address locations specifying a known reservoir name
or "pond at residence." The third vendor provided client addresses, but did not specify the pond
locations.
Based on the three responses received, there were approximately 200 individual stocking
incidences for various nonnative, nonsalmonid fish species from 1998 to 2000 in Colorado west
of the Continental Divide. Using this rate of stocking activity from the three respondents, it was
estimated that an additiona1400 stocking incidences of nonnative, nonsahnonids may have
occurred, based on presumed sales for the six non-respondents, during 1998-2000 for which
records were unavailable to CDOW via voluntary submission.

In November 2002, a preliminary summary of this project was presented to the Colorado
Fish Health Board to provide an update on the project's progress, and to reiterate the low level of
response to the voluntary request for private stocking records. One private attendee at that
meeting indicated that the State's legal access to the stocking records (1998-2000) had expired,
and that there remained no recourse for requesting or acquiring the data. Given that response,
this report was finalized with the knowledge that much extant private stocking data for
nonnative, nonsalmonid fishes was inaccessible. Further, it was determined that this known
deficiency in the private sector stocking data would preclude any meaningful risk analysis of
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