9720

• UCREFRP Catalog Number: 9720
• Author: U.S. Fish and Wildlife Service.
• Title: Razorback sucker ‎(Xyrauchen texanus)‎ genetics management and captive propagation plan, Dexter National Fish Hatchery and Technology Center.
• USFW Year: 2004.
• USFW - Doc Type: Dexter National Fish Hatchery and Technology Center
• Copyright Material: NO

population extirpation (Maitland 1995). Hatchery programs are particularly important when
habitat alterations, such as those in the Colorado River, prevent wild populations from
reproducing and recruiting naturally (Maitland 1995). The goal in maintaining a refugium
broodstock and captive propagation program for RBS is to maintain, to the extent possible, the
genetic characteristics of wild fish in the captive populations. This requires a captive breeding
program that monitors and identifies all critical life history stages at which changes in genetic
composition as a result of culture practices may occur (Doyle et al. 1995).
This plan lists the genetic risk factors associated with maintenance of captive broodstocks
and captive propagation, and outlines strategies to identify, monitor and minimize the risk.
Breeding strategies and fish rearing practices are designed and conducted to reduce the effects of
drift, selection; inbreeding, outbreeding, and mutational load (Doyle 2001; Doyle et al. 1995).,
Maintenance of Genetic Refugia as a Captive Broodstock
Over 130 wild adult fish were captured in the early 1980s, and each fish was PIT tagged
and transported to Willow Beach NFH and Dexter NFHTC (Hamman 1985). Progeny from those
fish represent the `81 broodstock, and the genetic reserves of those wild individuals. Current
recovery efforts preclude the process of broodstock mining of adult fish from remaining Lake
Mohave RBS populations. However, the ongoing collection of naturally produced larvae from
throughout Lake Mohave provides a means of increasing the survival of naturally recruited fish,
and a protocol to ensure the genetic diversity of the RBS in Lake Mohave is adequately sampled.
For example, adult RBS congregate on spawning bars throughout the lake; larval fish taken from
those areas, if sampled throughout the spawning period, should reflect the genome of the current
Lake Mohave RBS reproducing population.
Fry taken from spawning sites that are destined for future broodstock are grown in aquaria
until large enough to PIT tag. Current studies at Dexter NFHTC are examining the use of VIE
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