| Threatened
Native Fish Gets Some Attention |
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 Background:
Roundtail chub, a minnow native to Arizona, have decreased in distribution
and abundance throughout their natural range. Prior to 2000, the Arizona
Game and Fish Department had few records of roundtail chub inhabiting
the lower Verde River below Bartlett Dam and the lower Salt River below
Stewart Mountain Dam. An intensive one-year sampling effort during
2001 revealed that roundtail chub in the lower Verde and Salt rivers
appear to have a relatively large (~6,500 individuals in both rivers),
stable population in the two rivers, even in the presence on nonnative
fish predators and competitors. However, there is some question as
to the validity of these population estimates because they were derived
from only one year of data. In addition, biologists are interested
in how this population continues to persist, while other populations
in Arizona continue to dwindle. This study was initiated to confirm
the 2001 population estimates and to collect data that will help us
better understand factors such as growth, survival, and movement of
roundtail chub in the lower Salt and Verde rivers.
Location:
This study is taking place below Bartlett Dam
(Bartlett Reservoir) on the lower Verde River,
and below Stewart Mountain Dam (Saguaro Lake)
on the lower Salt River. The rivers converge
at Phon D. Sutton Recreation Area and subsequently
feed into the Salt River Project canal system.
Approach:
 The
project resumes previous marking and recapture
efforts. Fish are initially captured at random
locations throughout both rivers during spring
using a canoe electroshocker and gill nets.
All roundtail chub captured are measured for
total length and weight, and injected with
a passive integrated transponder (PIT tag).
The PIT tag emits a frequency, that when activated
by a scanner, will return a unique 10 character
code. This allows each individual fish to be
identified if recaptured. In subsequent sampling
efforts, roundtail chub that are captured are
scanned for the PIT tag; length and weight
and collection location are recorded, as well
as the PIT tag number if the fish is a recapture.
Population size, and individual fish growth,
survival, and movement can be determined based
on the recapture of marked individuals. The
current study will continue through June 2004.
Benefits:
This research will allow us to gain a greater understanding of growth,
survival and mortality rates of roundtail chub in general, and to obtain
a more accurate population estimates of roundtail chub in the lower Salt
and Verde rivers. Because this species is in jeopardy of being listed on
the US Fish and Wildlife Service Endangered Species List, information gained
from this study will be useful in successfully managing and conserving
the species.
For more information
contact:
Scott Bryan, Arizona Game and Fish Department, 5000 W. Carefree Highway Phoenix, AZ 85086-5000
.
Phone: (623) 236-7250 E-mail: sbryan@gf.state.az.us |
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