Comparison of activity rates of 1+ yellow perch (Perca flavescens) from populations of contrasting growth rates using underwater video observations

Abstract

We compared the stereocinematographic (SCG) method to estimate activity rates of yellow perch (Perca flavescens) with the more traditional bioenergetic approach. We also compared activity rates of perch from two populations with contrasting growth rates to test the hypothesis that fish with lower growth rates are characterized by higher activity rates. We attempted to corroborate the SCG method by comparing values of energetic costs obtained with observations of fish movements with estimates obtained using the difference between field-derived consumption and growth rates (bioenergetic method). Independent estimates of consumption and activity rates were obtained for Lakes Hertel (average growth = 172 J·day-1) and Memphremagog (average growth = 595 J·day-1). Daily consumption rates averaged 720 J·day-1in Lake Hertel and 1457 J·day-1in Lake Memphremagog. SCG and bioenergetic methods provided similar activity estimates for Lake Hertel (<2.5% difference) and diverged by 0.4-82% for Lake Memphremagog depending on initial values of fish weight or consumption inputted in the bioenergetic equation. Regardless of the method employed, activity rates of fish from Lake Hertel were proportionally higher (24% of consumption rates) than those from Lake Memphremagog (on average 13% of consumption rates). Our work supported the suggestion that populations with slower growth rates may be associated with proportionally higher activity rates.