7880

• UCREFRP Catalog Number: 7880
• Author: Wydoski, R. S.
• Title: Augmentation Plan For Razorback Sucker In The Middle Green River, 1996-1997.
• USFW Year: 1996.
• USFW - Doc Type: \
• Copyright Material: NO

basin and backwaters do not appear to produce sufficient numbers of
zooplankton that are needed for survival of the razorback sucker during their
critical larval period (Grabowski and Hiebert 1989; Mabey 1993; Papoulias and
Minckley 1990). While the production of zooplankton is excellent in
off-channel flooded bottomland habitats, these habitats have been disconnected
from the main channels by levee construction. The current Recovery Program
direction is to enhance or restore flooded bottomland habitats so that larvae
can survive until the present recruitment bottleneck is removed.

IV. GOALS AND OBJECTIVES

The primary goal of this augmentation stocking plan is to increase the numbers
of adult razorback suckers with the intent of stabilizing the Middle Green
River stock from the present estimate of 500 fish to 1,000 fish.

The main ,objective is to augment the number of adult razorback suckers in the
Middle Green River by 500 fish through augmentation stocking.

v. APPROACH

Overview. In 1994, the Biology Committee approved trapping of wild razorback
sucker larvae in a manner to maximize the genetic contribution of the wild
adult population and to stock such larvae into controlled flooded bottomlands.
Because access to flooded bottomland habitats to drifting razorback sucker
larvae from natural spawning in the main channels is limited, the transfer of
wild larvae (i.e., larvae from natural propagation) into intensively managed,
predator-free ponds, provides an excellent option for rearing fish to augment
the Middle Green River razorback sucker stock. Guidelines for maintaining
genetic diversity in wild larval endangered fish to be stocked and reared in
protected environments are provided in the. Genetics Management Guidelines
(Williamson and Wydoski 1994; pages 14-15).

StrateQY. A combination of razorback suckers from natural spawning in the
Middle Green River and razorback suckers from pedigreed family lots will be
stocked into the Middle Green River to augment wild razorback sucker numbers
in this reach.

During 1995, 944 captive-reared razorback suckers from 5 family lots
(approximately 200 fish from each family lot) were stocked into the Middle
Green River. Equal numbers of all captive-reared family lots will be stocked
in the future following the Genetics Management Guidelines (Williamson and
Wydoski 1994) to prevent genetic swamping of the wild razorback sucker stock.

Intensive collections of wild razorback sucker larvae will be made in the
Middle Green River using light traps. All larvae collected will be stocked
into 0.2-acre ponds at the Ouray National Fish Hatchery. A spatial and
temporal sampling scheme will be used to allow the random selection of larvae
to maximize the genetic diversity of progeny from natural spawning. Larvae
will be collected over a minimum of six weeks at several sites near Ouray as
part of the larval razorback sucker monitoring effort.

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