9465

• UCREFRP Catalog Number: 9465
• Author: Burdick, B.
• Title: Monitoring and Evaluating Various Sizes of Domestic-Reared Razorback Sucker Stocked in the Upper Colorado and Gunnison Rivers
• USFW Year: 2003.
• USFW - Doc Type: 1995-2001.
• Copyright Material: NO

an effective and timely means to restore wild razorback sucker populations in river reaches
designated within the Genetic Management Plan (Wydoski 1995) and essentially would
accomplish three objectives: 1) restore populations of razorback sucker to unoccupied river
reaches, 2) augment very small populations in occupied reaches, and 3) establish a minimum
viable population of at least three adult age groups (5 to 7) at the population abundance criteria
developed within the recovery goals for the razorback sucker (FWS 2002).
Summary of Razorback Sucker Experimental and Augmentation Stocking Plans
The RPs for the Upper Colorado River and the San Juan River basins each required that a
stocking plan be approved before any domestic-reared fish could be stocked into the wild.
Experimental stocking and augmentation plans for the razorback sucker were initially developed
for the Upper Colorado and Gunnison rivers in Colorado (Burdick 1992; Burdick et al. 1995) and
the San Juan River in New Mexico and Utah (Ryden and Pfeifer 1994). Burdick (1992) and
Ryden and Pfeifer (1994) addressed the essential elements for an experimental stocking program
to obtain fundamental information on the ecology of razorback sucker to determine the feasibility
and utility of augmentation or restoration stocking as a recovery tool. These were conceptual
plans that also discussed the rationale and justification for experimental stocking, the genetic and
ecological risks associated with experimental stocking, justification for selection of stocking areas,
and the protocol and criteria to investigate the relation between size at stocking and their
subsequent survival in the wild. The plans also outlined research efforts and general procedures
to monitor stocked fish and evaluate a stocking program.
Once it was demonstrated or believed that experimentally stocked fish would survive and
suitable habitat existed to support sub-adult and adult fish, additional plans evolved to identify the
number and size of fish needed to evaluate the relation between survival to size at release, and the
number of adult fish needed per river reach to achieve recovery. Modde et al. (1996) discussed
an augmentation plan for razorback sucker in the Upper Colorado River Basin coincident with
environmental enhancement. Individual plans were developed for the San Juan (Ryden 1997) and
Upper Colorado and Gunnison rivers (Burdick et al. 1995) and identified additional monitoring
for various sizes of stocked razorback sucker for up to 5 to 6 years. A restoration plan to
augment present razorback sucker populations was developed for the middle Green River in Utah
(Wydoski 1996).
The States of Colorado (Kesler 1998) and Utah (Hudson et al. 1999) later developed their
own individual stocking plans for each of the four mainstem endangered fishes that refined the
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