Regarding Preliminary Results of the lssf
on Native Fishes in the Grand Canyon by Melissa Trammell, bqr 13:4
In the summer of 2000, the Bureau of Reclamation initiated a test of the
concept of Low Steady Summer Flows (lssf) called for in the 1995 Fish
and Wildlife Service Biological Opinion. The Grand Canyon Monitoring and
Research Center (gcmrc) was responsible, together with teams of collaborating
scientists, for developing the science plan to evaluate this experiment.
A scientific symposium to discuss the results of this experiment will
be convened in Flagstaff at the Little America Hotel on Thursday April
26 and Friday April 27, 2001. At that time, gcmrc and the scientists who
participated in the experiment will present their findings. We invite
bqr readers to attend this symposium.
In the meantime, an article in the December bqr reported preliminary results
of the lssf test on native fish in Grand Canyon. The author attributed
findings associated with native fish to steady flows and implies that
these flows were beneficial to native fish. The author provides qualifying
statements in many cases, but does not provide plausible alternative explanations
for the response observed this summer. Gcmrc feels a responsibility to
re-enforce the caveats contained in the article and emphasize that the
preliminary observations presented in the article are open to equally
plausible alternative explanations that should not be discounted before
a thorough analysis has been conducted.
Alternative interpretations for some of the information relayed in the
December article include:
a) Flannelmouth suckers may have pulled off a strong cohort that was coincidental
with a steady flow regime. There were large numbers of young native fish
in the mainstem in 1993 as well, but this occurred under a fluctuating
b) Water clarity in the mainstem was very high compared to previous years.
People could visually see large numbers of fish. But does this mean that
there were more fish?
c) The sampling effort was greater in 2000 than in previous years, which
may bias sample size.
d) Fathead minnows often spawn later than native fish, so one would expect
the numbers to increase over the summer.
e) Larval drift from upstream areas like Beecher Springs (in the mainchannel)
cannot be discounted. Young fish from the lcr are found below Tanner,
so why not from Beecher Springs to mile 197?
f) Is it possible that young fish would have
been found at mile 197 in other years if a similar monitoring effort had
g) We cannot presently separate lcr recruitment effort from mainstem recruitment
except by making spatial assumptions.
h) To make conclusions of success or failure based on a single event does
not permit the exclusion of other hypotheses for the success of a years'
Science is a process of hypothesis testing, discovery and dissemination.
Gcmrc and its collaborating scientists are excited by the lssf test and
the contribution the results of this experiment will make to our understanding
of the Colorado River ecosystem. We remain cautiously optimistic about
the apparent benefits of the lssf test; at the same time we encourage
everyone who is concerned with the health of the Colorado River ecosystem
to be patient as we and our collaborating scientists evaluate the results
of this experiment. One lesson from the 1996 experiment is that initial
interpretations may change as more analysis is conducted.
The bqr is a journal that promotes understanding of the Colorado River
and its environs and we applaud its contributors and the interests of
those who subscribe to it. As for lssf and native fish, more data may
need to be analyzed before any trends become obvious and the essential
data may require many more years of effort to collect.
We applaud the hard work of the collaborating scientists who helped make
the lssf experiment a success and we look forward to hearing a more complete
analysis of the data that has been collected at the April Science Symposium.
We hope to see many of you there.
Barry D. Gold, Chief gcmrc