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

sampling of random molecular markers does not conclusively have a direct correlation with
fitness of populations or individuals (Waples 1991 a), high levels of molecular variation provide
"strong evidence" that the chance for adaptive potential exists (Lynch 1996; Lynch et al. 1998,
but see Pearman 2001 and Milligan at al. 1994). Lynch suggests the goal of maintaining 90% of
genetic variation is a short-term goal and that long-term maintenance of evolutionary potential
should focus on a population size that allows the average genetic variance to become
independent of population size. A genetically effective population size of 1000 (Ne), which
corresponds to a total population size of between 5,000 and 10,000 breeding adults is a realistic
goal to attempt to defray the effects of mutational load, drift, and selection (Lande 1995; Lynch
1996). However, Lynch (2001) theoretically outlines substantial problems with mutational load
and domestication selection even in large captive populations. Other empirical research
suggests that additive genetic variance, which is directly correlated with many fitness
components; has been shown to increase when populations expand after a bottleneck event
(Goodnight 1988). Given those caveats, while any one facility does not have room or funding to
maintain 10,000 adult RBS, collectively the five facilities (Ouray NFH, Dexter NFHTC, Willow
Beach NFH, Grand Valley Endangered Fish Facility and Wahweap SFH) involved in RBS
recovery could approach that optimum total population size.
Our goal is to maintain a minimum pool of 3,000 adults at Dexter NFHTC that will be
used in a rotational pedigree breeding program to ensure production fish will represent the
genome of the RBS, and most importantly, not adversely affect the Ne or fitness of wild RBS
populations (Ford 2002; Lande 1995; Lynch et al. 1998; Ryman and Laikre 1990; Laikre and
Ryman 1996; Doyle 2001). To that end, collections of wild caught larvae and paired matings of
the '81 broodstock will continue until sufficient individuals are held to meet the target of 3,000
adult broodstock. Dexter NFHTC broodstock development has encompassed more than two
decades, and will continue as outlined above. This process will achieve adequate representation of
22