Phenology of Annulus Formation in Walleye and Smallmouth Bass Otoliths

Abstract

Abstract:Walleye Sander vitreus and smallmouth bass Micropterus dolomieu were sampled monthly (May-October) from Lake Sharpe, South Dakota during 2006 and 2007 to estimate the timing of otolith annulus formation and to evaluate the influence of fish age, sex, and sample location (walleye only) on the timing and detection of annulus formation. Timing of annulus formation was evaluated using marginal increment analysis. Walleye samples were stratified by age, sex, and sample location (i.e., upper and lower Lake Sharpe) and smallmouth bass samples were stratified by age and sex. Monthly mean marginal increment measurements for both species generally increased from May to June, declined in July, and slowly increased from August to October. Although monthly differences in marginal increment measurements across analysis strata were rarely consistent, July generally had the lowest mean marginal increment across species and strata, suggesting that annulus formation in walleye and smallmouth bass in Lake Sharpe likely occurs in July. The lack of differences in timing of annulus formation across species-specific strata was surprising given the well-known influences of age, sex, and water temperature on somatic growth. Nonetheless, results will aid managers in improving the accuracy of age estimates.

Otolith chemistry indicates walleye movement and entrainment in a large serial reservoir system

“…In addition, adult otoliths were ablated on the outer edge of each annulus to ascertain yearly site occupancy and thereby assess annual intra‐ and inter‐reservoir movement patterns. Research on the timing of walleye annulus formation indicates that annuli form in late summer (July, August) in Missouri River reservoirs (Graff, Dembkowski, & Wuellner, ). Thus, adult element:Ca signatures reflected the sites fish occupied in late summer and were temporally matched with water sample collection in late summer 1982–1989 and late summer 2012.…”

“…In addition, adult otoliths were ablated on the outer edge of each annulus to ascertain yearly site occupancy and thereby assess annual intra-and inter-reservoir movement patterns. Research on the timing of walleye annulus formation indicates that annuli form in late summer (July, August) in Missouri River reservoirs (Graff, Dembkowski, & Wuellner, 2014 water element:Ca signatures may have been inconsistent with pre-and post-flood ratios (Voss et al, 2014). Temporal separation between the flood and annulus formation precluded the need for water sample collection during dangerous flood conditions and enabled evaluation of flood-induced movement and entrainment patterns.…”

Effects of the 2011 Missouri River flood on walleye natal recruitment and habitat use in Lake Sharpe, South Dakota

“…Age-0 and age ! 1 otoliths were spot-ablated along transects encompassing the core (representing natal origins), the outer edge of each annulus (representing late-summer habitat use for Missouri River walleye; Graff et al 2014), and the terminal edge. Temporal matching of water and age-0 otolith signatures was a requirement for evaluating natal recruitment and habitat use of age !…”

“…1 walleye were also temporally matched with late-summer water sampling (both historical and current) because otoliths were ablated on the outer edge of each annulus (i.e. late-summer habitat use; Graff et al 2014). Moreover, because floodwaters declined from peak levels in mid-May through June, late-summer otolith signatures of age !…”

“…July-September) habitat use in the habitat types listed above before, during, and after the flood year. Emphasis was placed on late-summer habitat use due to an otolith ablation protocol (see Methods) that focused on annuli, which form in late summer for Missouri River walleye (Graff et al 2014). It was hypothesized that floodplain habitats (e.g.…”