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| From the
1999 Southern Division of the American Fisheries Society Midyear Meeting held in
Chattanooga, Tennessee. |
Evaluation of a 254-mm Size Limit
and Stocking as Management Strategies for Tennessee Reservoir Crappie Fisheries
Daniel A. Isermann, Phillip W. Bettoli, and Steve M.
Sammons Tennessee Cooperative Fishery Research Unit Tennessee Technological University Box
5114 Cookeville, Tennessee 38505 Voice 931-372-3094 FAX 931-372-6257 E-Mail dai7422@tntech.edu,
pbettoli@tntech.edu, ssammons@tntech.edu
Keywords: crappies, size limit, modeling, stocking,
oxytetracycline
The Tennessee Wildlife Resources Agency recently implemented a 254-mm
size limit on crappie Pomoxis spp. fisheries statewide and has stocked up to 1.5
million crappie per year for the past six years. In October 1997 we began investigating
the response of reservoir crappie fisheries to the size limit and the efficacy of
Tennessee’s crappie stocking program. Effects of the size limit on crappie harvest in
two Tennessee reservoirs were simulated using a Beverton-Holt equilibrium yield model.
Simulations indicated yield in Douglas Reservoir would be increased with a 254-mm limit
over a range of conditional natural (CM) and conditional fishing mortality (CF) rates,
however, the benefits of the size limit declined as CM increased. Yield in Normandy
Reservoir was maximized by the size limit over a wide range of exploitation rates when CM
was low (~ 30 %). At higher CM rates (40 - 50%), improvements in yield were only apparent
at high exploitation rates (50 - 80%). When CM exceeded 50%, yield was maximized with no
size limit. In fall 1997 age-0 black-nosed crappies P. nigromaculatus (BNC)
were marked with oxytetracycline (OTC) and stocked into Normandy Reservoir. Analysis of
otoliths taken from age-1 BNC collected in August 1998 rotenone samples showed marking
efficacy to be 98% and stocked crappies represented 90% of age-1 crappies in those
rotenone samples. In May 1998 50,000 BNC were OTC- marked and stocked into Old Hickory
Reservoir; their contribution to age-0 catch rates in fall 1998 trapnets will be reported.
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