Jarnagin, S. U.S. Environmental Protection Agency, ORD/EPIC, jarnagin.taylor@epamail.epa.gov
Swan, B. San Diego State University, swain@rohan.sdsu.edu
Kerfoot, W. Michigan Technological University, wkerfoot@mtu.edu

 
TESTING THE EGG RATIO: PELAGIC VS SEDIMENTARY RECORDS OF SECONDARY PRODUCTION OF BYTHOTREPHES CEDERSTROEMI IN AN INLAND LAKE
 
The Edmondson-Paloheimo egg ratio has been the primary method used to calculate secondary production for many species of zooplankton for decades. There are several assumptions that the egg ratio is based upon (exponential growth, stable age distribution, etc.). These assumptions are rarely met in nature. While there have been numerous theoretical tests of the egg ratio based upon modeling, this research is the first direct test of the egg ratio. Bythotrephes cederstroemi does not over-winter in northern latitudes and at birth possesses a caudal spine that is not shed during molting. The spines quantitatively pass through fish and are preserved in lake sediments. This allows for a direct estimate of seasonal production and mortality to be made from sediment traps. Egg ratio predictions of production based on pelagic sampling of Bythotrephes in Lake Michigamme, MI were compared with sedimentary samples for 1995 and 1996. In spite of many violated assumptions, the number of spines predicted by the egg ratio agreed well with the number collected in sediment traps. Our data show that the Edmondson-Paloheimo egg ratio is a robust estimator of secondary production and works reasonably well even when the assumptions upon which it is based are moderately violated.
 
Day: Wednesday, Feb. 3
Time: 04:15 - 04:30pm
Location: Eldorado Hotel
 
Code: SS18WE0415E