Usefulness of Otolith Weight for EstimatingAge‐BasedLife History Metrics of Lake Trout

Abstract

AbstractTo determine if otolith weight can be used to accurately and precisely estimate age‐based life history metrics of Lake TroutSalvelinus namaycushpopulations, we quantified relationships between Lake Trout otolith age and weight sampled from a wide geographic and size range of North American lakes. Separate nonlinear age–weight models for each of 22 surveys (each year within each area or lake) described 82.8% of variation in the relationship between otolith age and weight, whereas separate age–weight models for each of 13 lakes or areas within lakes (years combined) described only 0.4% less variation. Over all surveys, age increased at an average rate of 1.13 years per milligram increase in otolith weight and the otolith weight–age relationship was significantly nonlinear. Age of individual fish could not be estimated accurately from otolith weight alone, although bias of mean age estimated from mean otolith weight was small, whether using survey‐specific or general otolith age–weight relationships. Age at maturity and survival derived from indirect otolith age–weight relationships were estimated with less bias than growth parameters. We conclude that a general model for estimating Lake Trout age from otolith weight may be more useful for maturity and survival analyses that are less susceptible to estimation error of individual (often old) fish than for growth analysis that can be susceptible to estimation error of individual (often old) fish.