DETECTING CHANGES IN CHANNEL CATFISH (ICTALURUS PUNCTATUS)
POPULATIONS WITHIN THE LONG TERM RESOURCE MONITORING PROGRAM'S
STUDY POOLS.

Randy Burkhardt. U.S. Geological Survey, Upper Midwest
Environmental Sciences Center, Onalaska, WI 54650.  

Field staff of the Long Term Resource Monitoring Program (LTRMP)
has collected randomly sampled fish data in Mississippi River
Pools 4, 8, 13, 26, an open river reach, and La Grange Pool of
the Illinois River since 1993, but the ability to use these data
to detect trends or changes in fish populations has not been
quantified.  To address this issue, a power analysis was
completed using "pool-wide" catch-per-unit-effort (Cf) means from
the LTRMP channel catfish data.  The power analysis calculated
the ability to detect a 10% or 30% annual change in the pool-wide
Cf mean produced by several gears; day electrofishing, fyke
netting, mini fyke netting, seining and large and small hoop
netting.  Power of detection varied with pool location and year,
but generally the LTRMP day electrofishing and large and small
hoop netting data will detect a 30% annual change in channel
catfish within a 96% probability (average; all pools).  In La
Grange Pool, Open River reach, and Pool 26, a 10% annual change
in channel catfish population sampled by day electrofishing or
large or small hoop netting had a detection probability of 74%
(average; 1993 omitted).  In the northern study pools (4, 8, 13)
where channel catfish are less abundant, a 10% population annual
change had a 50% probability of detection (average; 1993
omitted).  Of all of the LTRMP gears used, day electrofishing was
the most consistent and had the greatest probability of detecting
annual channel catfish population changes (10% changes = 75%
probability; 30% changes = 96% probability) in all pools.  

Keywords:  channel catfish, fish, Mississippi River, Long Term
Resource Monitoring Program, Ictalurus punctatus