Evaluation of riverine smallmouth bass recruitment indices on Pennsylvania rivers

Since 1987 the Pennsylvania Fish and Boat Commission (PFBC) sampled smallmouth bass, Micropterus dolomieu, young of year (Y-O-Y) using near-shore daytime back-pack electrofishing on selected major rivers throughout Pennsylvania.  Additionally, the PFBC sampled yearling and older smallmouth bass on these rivers, periodically, since 1990, using nighttime standardized flat bottom boat electrofishing.  A “best” smallmouth bass recruitment index was identified through use of a mixed-effects ANCOVA model, where we related several recruitment catch rate indices (age 0, age 1, and age 2) to older age group catch rates, up to age 4, of the same year class.  All catch rate data was log₁₀ transformed.  The yearling (age 1) catch rate index explained the most variation in catch rate of age 2 through age 4 smallmouth bass of the same year-class.  The Y-O-Y index (age 0) and age 2 index both explained less variation in catch rate of older age classes.  All recruitment catch rates examined explained less than 50% of the variation in catch rate of older age classes.  Generally, any age class recruitment catch rate index explained the most variation in the catch rate of smallmouth bass of the next older age of the same year-class.