Evaluation of the Aging Precision of Anal Spines and Scales for Smallmouth Bass

Smallmouth bass (Micropterus dolomieu) are an important part of the recreational fishery in northern Lake Michigan. Age estimates are used to determine age structure, growth rates, age at maturity, and other demographic parameters required for management decisions.  Due to their use in management, precise age estimates are critical.  However, the precision of smallmouth bass aging structures has not previously been evaluated.  Sacrifice of fish in smallmouth bass fisheries could be avoided if an appropriate non-lethal aging structure was determined.  The objective of this study was to determine and compare the precision of two non-lethal aging structures, anal spines and scales, for smallmouth bass in northern Lake Michigan.  Because known age smallmouth bass were unavailable for this study, precision, rather than accuracy, is a more practical method of evaluation. Preliminary results indicate that there is not a significant difference between the precision of anal spines and scales of smallmouth bass.  When incorporating processing times scales appear to be most appropriate aging structure.  Further investigation is needed to determine if precision varies significantly between the two structures.  This study will allow us to determine the most appropriate aging structure for smallmouth bass, resulting in more precise age estimates for management decisions.