7837

• UCREFRP Catalog Number: 7837
• Author: Aquatic Nuisance Species Task Force.
• Title: Report To Congress, Findings, Conclusions, and Recommendations of the Intentional Introductions Policy Review.
• USFW Year: 1994.
• USFW - Doc Type: \
• Copyright Material: NO

degradation may make a species more vulnerable
to the introduction of nonindigenous species.
Moyle and Williams (1990) analyzed the status
of native fish species in California. They deter-
mined that large water projects, in concert with
introductions of fish species better able to cope in
altered habitats, were largely responsible for the
decline of California's fish fauna. The presence
of introduced species was a "very important fac-
tor" or the "principal" factor in the status of 49%
of those species described as extinct, endan-
gered, or in need of special protection.
Miller et al. (1989) analyzed factors associated
with the extinctions of three genera, 27 species,
and 13 subspecies of North American fishes in
the past 100 years, many of which occurred
before the passage of the Endangered Species
Act in 1973. In most cases, multiple factors were
cited. Habitat alteration was cited in 29 (73%) of
the 40 extinctions, and introduced species were a
contributing factor in 27 (68%) of the cases. For
those cases where introduced species were cited,
19 were apparently the consequence of inten-
tional introductions, as defined herein
(Appendix C).
Similar to the Miller analysis, a review of factors
cited in the listings of 92 fish species under the
Endangered Species Act (ESA) was conducted in
conjunction with this report (Appendix D). The
review identified that in most of the 69 cases for
which adequate information was provided, more
than one listing factor was cited. Among these
cases, habitat alteration again appeared as the
most frequently cited factor in 63 (91%) of the
69 listings. The effects of introduced species
were cited as a cause of decline or potential
threat in 48 (70%) of the 69 cases. Introductions
related to sport fishing (game, forage, and bait
species) were the most commonly cited (35 of
the 48 cases). A majority of the introduced
species cited appear to have been present in the
ecosystem as the result of intentional introduc-
tions; again, as defined herein.
Introduced species have impacted indigenous
fish species, whether habitat modification has
occurred or not. In six of the ten cases where
Miller et al. (1989) cited introduced species as a
"major" or "primary" factor in the extinction of
native fishes, habitat alteration was not a cited
factor. Similarly, the desert pupfish (Cyprinoclon
macularius) is listed as endangered throughout
its range of southeastern California and southern
Arizona. Reasons for its decline include: habitat
loss, habitat modification, and pollution
(USFWS 1993). But as the USFWS Desert
Pupfish Recovery Plan states, "pupfish do not
fare well in the presence of non-native fishes and
incursions by exotics have typically resulted in
decline or extirpation of pupfish" (USFWS
1993) .
The spread of pathogenic organisms has not gen-
erally been attributed to intentional introduction
of the pathogen (e.g., for research purposes) but
in association with shipments of artificially reared
organisms (Andrews 1980, Rosenthal 1985,
Farley 1992). As pointed out in a summary of
disease introductions by Sindermann (1993), a
variety of serious diseases with major economic
impact have been moved about accompanying
organisms used in stocking programs or aqua-
culture programs. Such diseases have had an
impact on a variety of organisms ranging from
penaeid shrimp to salmonids to oysters. Even
introductions of the same or closely related
species can have negative impacts on native pop-
ulations through the introduction of pathogens
or parasites that may cause epizootics. Wild and
farmed populations of Atlantic salmon in Norway
have been devastated by the introduced mono-
gean parasite Gyrodactylus safaris (Johnsen and
Jensen 1991). Infectious hematopoietic necrosis
virus appears to have been introduced into Japan
with sockeye salmon eggs in the 1970s and has
since affected the native masou salmon
(Oncorhynchus masou). Similarly, when the
American crayfish (Pacifastacus leniusculus) was
introduced into Europe it brought with it the
crayfish plague (Aphanomyces astaci). This fun-
gal disease has little impact on the American
crayfish within its native range but has eliminated
the native crayfish from much of Europe
(Thompson 1990). Pathogens and parasites
associated with introduced species may also have
an impact on species that are not released to the
wild as in the case of the highly lethal shrimp
virus infectious hypodermal and hematopoietic
necrosis virus (IHHNV). Introduced into aqua-
culture facilities in Hawaii, Florida, Texas,
Guam, and most recently Mexico, IHHNV has
had a major economic impact on aquaculture
facilities whenever it has been introduced
(Lightner et al 1992).
Though such introductions would under the lan-
guage of the Act be considered unintentionally
introduced species, they are obviously inextrica-
blylinked to the organism that is being intention-