7775

• UCREFRP Catalog Number: 7775
• Author: Carlson, C. A. and R. T. Muth.
• Title: Inland Fisheries Management in North America, Chapter 15
• USFW Year: 1993.
• USFW - Doc Type: Endangered Species Management.
• Copyright Material: YES

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CHAPTER 15

endangered fishes, or any endangered species, should first avoid extinction and
then maintain the ability of fishes to adapt to changing environments and their
capacity for continued speciation. Maintaining genetic variability and evolution-
ary flexibility in small populations depends on maximizing within-population and
among-population variance. To accomplish this for endangered fishes, Meffe
(1986) recommended the best approximation to the following set of management
guidelines: (I) genetic monitoring should be done to determine how variation is
distributed within a species and how to preserve it, (2) the largest feasible
genetically effective population size should be maintained in captive breeding
programs, (3) if a large population cannot be maintained, inbreeding may be
avoided by selective mating, (4) stocks should be kept in hatchery environments
for as short a time as possible, and (5) separate stocks of isolated populations
should be maintained to preserve interpopulation variance.
Meffe (1987) argued that fisheries biologists must become more aware of
conservation genetics and incorporate it into fish conservation programs if they
expect to make a contribution to the preservation of biotic and genetic diversity.
He also urged that a conservative approach to conservation genetics be followed.
Conservation offish gene pools is limited by lack of genetic information on fishes,
facilities for storing fish genomes, experience in breeding and rearing many
species, understanding of the effect of genetic heterozygosity on individual
fitness, and information on how fish life histories can affect the genetic structure
of populations. Soule (1985) noted that the new field of conservation biology,
which is devoted to preserving biological diversity and addresses biology of
species, communities, and ecosystems perturbed by human activities, is often a
crisis discipline. In such disciplines, decisions must often be made in haste and
without benefit of knowing all the facts. Because the science of conservation
genetics is also new, and there is often uncertainty about necessary and sufficient
conservation methodology, retention of maximum global genetic diversity for
future research and management represents the conservative approach (Meffe
1987) .
Although fish seem to have been somewhat ignored by conservation biologists
(Allendorf 1988), a few recent studies emphasize the importance of genetic
analyses in their conservation. Meffe and Vrijenhoek (1988) developed two
models of isolation and gene flow to address how the population genetic structure
of desert fishes relates to programs for their recovery and conservation. The
authors urged use of three types of experimental research on population genetics
and fitness to allow prediction of survival and long-term success of remnant
populations of endangered and threatened fishes. Echelle et aI. (1989) observed
that most between-sample gene diversity in their work on Pecos gambusia was
due to differences among populations in the four primary areas where the fish
occurred. Maintaining the species in all four areas will ensure maximum allelic
diversity and also protect genetic diversity in other members of the communities
of which Pecos gambusia are a part. The review by Simons et al. (1989) of plans
to downlist the Gila topminnow also demonstrated the importance of maintaining
diverse relict populations.
A different approach is needed in conservation programs when most alleles are
distributed throughout the range of a species and little genetic divergence exists
between regions within its general range. Allendorf and Leary (1988) found that
conservation of some subspecies of cutthroat trout requires maintenance of many