Otolith Daily Increment Deposition in Age-0 Smallmouth Bass Reared in Constant and Fluctuating Water Temperatures

Abstract

We reared embryos and larvae of Smallmouth Bass Micropterus dolomieu in constant and diel fluctuating water temperatures (mean of 20°C) to clarify when otolith first daily increments were deposited and the periodicity of increment formation. Unlike the results of previously published studies, we found that first-increment formation began at hatching rather than 7–11 d later at swim-up. We confirmed that increment deposition was daily and extended the daily increment validation period from 21 d to 30 d posthatch. Accurate and precise age estimation was possible for Smallmouth Bass reared in both constant and fluctuating temperature environments, as age estimates rarely varied more than 1 d from true age. We also found consistent estimated ages using either left or right sagittae and showed relationships for Smallmouth Bass total length as a function of age, and otolith diameter as a function of total length. Otolith daily increment counts allow accurate and precise estimates of Smallmouth Bass age, which enables determination of hatch date, timing of spawning, and growth rate. These findings may assist with the management of this species, as well as provide information that can be used to disadvantage reproductive success of invasive Smallmouth Bass.

Received October 31, 2013; accepted March 28, 2014

ACKNOWLEDGMENTS

We thank J. McKissick and B. Egloff of Colorado Parks and Wildlife, Warmwater Fish Hatchery in Wray, Colorado, for assistance in obtaining Smallmouth Bass embryos. We also thank J. Fowler and J. Charles for assistance with embryo collection and laboratory activities, D. Propst, and anonymous reviewers for helpful comments on the manuscript. This is Larval Fish Laboratory Contribution 176.