8071

• UCREFRP Catalog Number: 8071
• Author: Horn, M. J. and P. C. Marsh.
• Title: Production of Razorback Sucker in a Backwater at Yuma Cove, Lake Mohave, Arizona and Nevada, 1992.
• USFW Year: 1993.
• USFW - Doc Type: Tempe, Arizona.
• Copyright Material: NO

10

recovered when the 2 dead fish found subsequent to poisoning are

included). Thus, our estimates based upon 6 mark-recapture samples

predicted 93 to 111% of the actual total harvest of young fish, and

must be considered a highly accurate predictors of actual abundance

on 29 July.

It is notable that only 64% (34 of 53) of marked individuals were
recovered subsequent to 22 July (when marking was discontinued).
This result was attributed to mortality coincident with the period
of poor water quality (high temperature and low dissolved oxygen)
in June and especially early July (Figures 3-4). Fish captured
during that time were in poor condition (visibly emaciated, high
infestation of parasitic Lernaea), and mean growth was demonstrably
reduced (Table 1, Figure 1). Using our SChumacher-Eschmeyer
estimate of 329 (251-472) fish on 29 July as a baseline, and
assuming that subsequent survival was 64% (based upon recovery of
marked fish), we would predict a final harvest of about 211 fish
(140% of actual). This last estimate is well within the
extrapolated 95% confidence limit range based upon 64% survival
(i.e., 161 to 302 fish). MUltiple-census techniques applied here
provided reasonable results, and can be used reliably in the future
to assess razorback sucker abundance in rearing and grow-out
backwaters and coves at Lake Mohave.