Age, Year-Class Strength Variability, and Partial Age Validation of Kiyis from Lake Superior

Abstract

Age estimates of Lake Superior Kiyis Coregonus kiyi from scales and otoliths were compared and 12 years (2003–2014) of length frequency data were examined to assess year-class strength and validate age estimates. Ages estimated from otoliths were precise and were consistently older than ages estimated from scales. Maximum otolith-derived ages were 20 years for females and 12 years for males. Age estimates showed high numbers of fish of ages 5, 6, and 11 in 2014, corresponding to the 2009, 2008, and 2003 year-classes, respectively. Strong 2003 and 2009 year-classes, along with the 2005 year-class, were also evident based on distinct modes of age-1 fish (<110 mm) in the length frequency distributions from 2004, 2010, and 2006, respectively. Modes from these year-classes were present as progressively larger fish in subsequent years. Few to no age-1 fish (<110 mm) were present in all other years. Ages estimated from otoliths were generally within 1 year of the ages corresponding to strong year-classes, at least for age-5 and older fish, suggesting that Kiyi age may be reliably estimated to within 1 year by careful examination of thin-sectioned otoliths.

Received January 17, 2017; accepted June 26, 2017 Published online September 6, 2017

ACKNOWLEDGMENTS

The R/V Kiyi crew (Charles Carrier, Lori Evrard, Dalton Lebeda, Keith Peterson, and Joe Walters) assisted with fish collections. Taylor Stewart and Matthew Belnap assisted with initial otolith preparation. Lori Evrard assisted with data management and presentation. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. All sampling and handling of fish were carried out in accordance with American Fisheries Society guidelines for the care and use of fishes (http://fisheries.org/docs/wp/Guidelines-for-Use-of-Fishes.pdf).