Use of striped bass egg
surrogates to assess gear detection thresholds and sampling efficiency
in the Savannah River Estuary
Ted A. Will, Thomas Reinert
Georgia Cooperative Fish and Wildlife Research Unit, D.B.
Warnell School of Forest Resources, University of Georgia, Athens, GA
30602-2152, Phone: 706-542-5260, Fax: 706-542-8356 email: twill@smokey.forestry.uga.edu,
treinert@uga.edu
Cecil A. Jennings
United States Geologic Survey - Biological Resources Division,
Georgia Cooperative Fish and Wildlife Research Unit, D.B. Warnell
School of Forest Resources, University of Georgia, Athens, GA
30602-2152 Phone: 706-542-5260, Fax: 706-542-8356, jennings@smokey.forestry.uga.edu
The abundance of striped bass eggs in the Savannah River Estuary (SRE)
declined in the 1980's and has remained low. Historically, the
majority of these eggs were collected in the Front (FR) and Back
Rivers (BR), but data on gear detection thresholds and efficiency of
egg collection methods are non-existent. Typically, evaluations of egg
abundances in the SRE were limited to comparing relative changes in
the spatial and temporal densities of eggs. Estimates of the actual
number of eggs at large have been unobtainable. Gellan ® flavor beads
are similar in shape, size, and specific gravity to striped bass eggs
and behave similar to eggs floating in a river. In the spring of 1999,
we used known amounts of these beads to determine the detection
threshold and efficiency of our egg sampling gear. We recaptured 49 of
the 5.1 million (~0.001%) beads released, which suggest that each egg
in our sample represented about 100,000 eggs in the SRE. This net
calibration technique will improve egg abundance assessment by
allowing the number of eggs in the estuary to be estimated. Also,
stronger inferences about the adequacy of striped bass egg production
during a spawning season are now possible.
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