Basin-wide predation mortality estimates:
The number of YP prey consumed across all sampled predators and both plumes was averaged
for each year (This included predators with no YP SNP signal, thus prey number = 0, raw data
available in the YP predation data file). We assumed the SNP and microsatellite assays have the
same temporal detection window as a previous molecular genetic stomach content study and thus
reflect the predation mortality during the 16 hours prior to sampling (Carreon-Martinez et al.
2011). Predation mortality means were then expressed as average consumption per fish per day
(24-hour period; Table 1). This was accomplished by dividing predation mortality means by 16
and then multiplying by 24. We determined the total abundance of our predator fish (yearling
Walleye and yearling and adult White Bass and White Perch) for each year using estimates from
the Lake Erie Forage Task Group 2011 and summing the abundances of all relevant year classes
of predator fish (Table 1; available online at: http://www.glfc.org/lakecom/lec/FTG.htm). The
estimates of per fish daily (24-hour) consumption estimates were then multiplied by the
estimates of predator fish abundance in each year to estimate the daily consumption of YP.
Table 1: Estimated predation mortality on larval Yellow Perch (YP) in the western basin of Lake
Erie, 2006-2008. AveYP/Pred/16hr: the average number of Yellow Perch prey items consumed
by one predator fish calculated by averaging YP numbers from all positive and negative YP
predators and both plumes for each year; AveYP/Pred/24hr: the average number of Yellow Perch
prey items consumed by one predator fish, extrapolated to a 24-hour period; NPred: estimated
number of predator fish (yearling Walleye, yearling and adult White Bass and White Perch) in
the western basin of Lake Erie (data from Lake Erie Forage Task Group 2011;
http://www.glfc.org/lakecom/lec/FTG.htm) and NYP Predated/24hr: extrapolated number of
larval YP consumed in a 24-hour period.
Year
AveYP/Pred/16hr AveYP/Pred/24hr NPred
NYP Predated/24hr
6
0.61
2006
0.92
106x10
98 x106
0.49
2007
0.73
44 x106
32 x106
6
2.73
2008
4.09
46 x10
189 x106