7786

• UCREFRP Catalog Number: 7786
• Author: Emlen, J. M., T. A. Strekal and C. C. Buchanan
• Title: Probabalistic Projections for Recovery of the Endangered Cui-ui
• USFW Year: 1993
• USFW - Doc Type: North American Journal of Fisheries Management
• Copyright Material: YES

472

EMLEN ET AL.

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10.000 acre-feet increments

rec lassify

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3,000 acre-feet increments

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0.8

0.7
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~ ~ ~ ~ 100
Supplementary water (x1 ,000 acre-feet)

120

FIGURE 2.-Probability of cui-ui population persistence (over 200 years) as a function of supplemental water
when water acquisition begins in 1994 and rises in yearly increments of 3,000 or 10,000 acre-feet. cui-ui could be
"de listed" as endangered at 0.95 probability of persistence or reclassified as threatened at 0.85 probability of
persistence.

vat ion measures listed in the recovery plan should
become mandatory (Strekal et at. 1992). At an 85%
probability of persistence , the IO,OOO-acre-foot in-
crement scenario leads to an eventual yearly level
of about 40,000 acre-feet (reachable by 1998), and
the 3,OOO-acre-foot increment program would
ultimately require about 50,000 acre-feet yearly
(reachable by 20 II) to achieve reclassification.

Discussion and Conclusion

The uncertainty in the amount of required sup-
plemental water, illustrated by the gap between
the upper and lower curves in Figure I, demon-
strates the critical need for better information on
early survival of the cui-ui. Model results should
be updated and refined as better estimates of sur-
vival become available. For the moment, we must
make do with the data we have. With this caveat,
two conclusions can be made.
First, acquisition of supplemental water before
the spring aggregation in 1991 in the amount (best
estimate) of 70,000 acre-feet would have led to
conditions allowing for eventual (after response
has been checked and documented) declassifica-
tion of the cui-ui.

Second, as the acquisition of supplemental wa-
ter becomes increasingly protracted, larger acqui-
sitions become necessary, delisting is progressively
postponed, and the risk of coincidental extinction
grows. If water acquisition were to begin in spring
1994 with 5,000 or fewer acre-feet per year and
incremented yearly by less than 5,000 additional
acre-feet per year, the eventual yearly input of sup-
plemental water required for recovery (interpo-
lated from Figure 2) would exceed realistic limits
on availability, making imposition of other con-
servation measures necessary.

References

Buchanan, C. c., and M. E. Coleman. 1987. The cui-
ui. Pages 425-436 in R. L. DiSilvestro, editor. Au-
dubon Wildlife Report. Academic Press, Orlando,
Florida.
Buchanan, C. c., and T. A. Strekal. 1988. Simulated
water management and evaluation procedures for
cui-ui (Chasmistes cujus). U.S. Fish and Wildlife
Service and Bureau of Reclamation, Reno, Nevada.
Chatto, D. A. 1979. Effects of salinity on hatching suc-
cess of the cui-ui. Progressive Fish-Culturist 4 I :82-
85.
Coleman, M. E., D. Winkelman, and H. L. Burge. 1987.