Client:
Results:
Staff:
GOAL
In 1996, Cramer Fish Sciences (CFS) implemented a juvenile salmonid out-migration
monitoring program at Caswell Memorial State Park on the lower Stanislaus River.
Operations by CFS have occurred annually at this site to estimate abundance of
out-migrating juvenile Chinook salmon (Oncorhynchus tshawytscha) and
steelhead/rainbow trout (O. mykiss) in order to understand the impacts of
instream flow schedules and management actions.
PROCESS
We used three rotary screw
traps (i.e., two configured side-by-side and one
located approximately 100 m
downstream) to capture out-migrants between January and June. We developed
abundance estimates by measuring trap efficiency, whereby a known number of
marked fish were released upstream of the traps and compared to the number of
recaptured marked fish. A predictive model was developed which used efficiency
data from previous years and the nine efficiency tests from 2007 to determine
daily trap efficiency.
STATUS
In 2007, CFS also implemented the pilot of a multiple year coded wire tag study
at the Caswell monitoring station. The main objectives of this study are to
determine the relative contribution of different life stages (i.e., fry/parr/smolts)
to the returning adult population, and to identify the prevalence of different
life history strategies of juvenile Chinook salmon in the lower San Joaquin
River and Delta. Columnaris (Flavobacterium columnare) infections
observed during the season were an important factor affecting operations,
procedures, and total numbers of tagged fish.
We are currently adapting our
operational protocol to incorporate investigations of fish health, and are
also considering supplementing the coded wire tag study with a novel approach,
using otolith microchemistry, to more fully address our main objectives. We
hope to compare the utility of these different methods, and apply these
techniques to drainages throughout the Central Valley.
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