Morphometric Differences of Yellow Perch within Management Unit 2 in Central Lake Erie

     Yellow perch Perca flavescens is a heavily exploited species in Lake Erie supporting thriving commercial and recreational fisheries.  Harvest is presently managed within four management units (MU), which are roughly aligned with the natural trophic gradient of Lake Erie, but which may not be aligned with stocks of yellow perch.  We examined whole-body morphometrics, which have been used successfully to distinguish fish stocks in the Great Lakes and elsewhere, to determine if yellow perch from four sites within Management Unit 2 are morphometrically similar.  We used bottom trawls to sample four cross-lake transects in MU2 (western half of the central basin) during spawning in early May 2009 to determine distribution of spawning yellow perch.  We used Principal Component Analysis (PCA), Discriminant Function Analysis (DFA), and ANOVA of axes from PCA to examine whole-body morphometrics of 392 adult male yellow perch from four locations, two in Ontario waters and two in Ohio waters, to determine if morphometrics varied within this management unit.  Only 17% of all fish captured, and no spawning fish, were captured in waters deeper than 23 m, which was over half  (> 33 km) of the sampled transects.  Spawning aggregations were most dense in water 15.2-18.2 m deep with mean temperature of 8 degrees.  Morphometrics varied most strongly between northern (Ontario) and southern (Ohio) sites but also weakly among sites.  Distributional and morphological data support the conclusion that there are different spawning stocks in northern and southern areas in MU2.  Barriers that maintain stocks likely include deep water, seasonal anoxia, and water currents.