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| From the
1999 Southern Division of the American Fisheries Society Midyear Meeting held in
Chattanooga, Tennessee. |
The Success of Grass Carp
Confinement and Impact of Aquatic Plant Enclosed Areas of Lake Seminole
Jeffrey W. Slipke and Michael J. Maceina, Department of
Fisheries and Allied Aquacultures, 203 Swingle Hall, Auburn University, Alabama
36849-5419; Voice 334-844-4058; FAX 334-844-9208; E-Mail jslipke@acesag.auburn.edu, mmaceina@acesag.auburn.edu
Keywords: grass carp, electrical barrier, radio
telemetry, aquatic vegetation, enclosures
We evaluated the success of three types of barriers used
to confine grass carp in enclosed embayments of 250 and 350 ha. Our objective was to
estimate escape rates of grass carp and to assess the impact of stocking 31 to 35 triploid
grass carp (> 304 mm TL) per vegetated hectare on submersed vegetation abundance within
these areas. Using radio telemetry, we determined that a funnel weir type barrier and a
boatable gate type barrier were ineffective at containing grass carp as evidenced by
respective verified annual escape rates of 9% and 23% and maximum potential escape rates
of 42% and 35%. Escape rates from the funnel weir enclosure were high enough that grass
carp did not reduce vegetation coverage over a two year period. However, a significant
vegetation reduction was observed in the boatable gate enclosure. The third barrier type
was the same funnel weir retrofitted with an electrical field array positioned within the
mouth of the funnel. This design yielded a maximum potential escape rate of 1.2% over a
nine month period and thus appears to be effective at confining grass carp. These results
may have implications concerning the feasibility of zoning lakes and reservoirs to
separate incompatible uses.
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