Investigating the Utility and Relative Accuracy of Nonlethal Ageing Structures to Age Two Nonnative (Brook Trout and Brown Trout) and One Native (Rio Grande Cutthroat Trout) Trout Species Collected in Carson National Forest, New Mexico

The utility of calcified structures to age fish varies among structures as well as species.  Additionally, the use of lethal or nonlethal ageing structures may play a central role in the feasibility of gathering age data for some species that may be recreationally important or threatened.  The primary purpose of this study was to investigate the utility of scales, pelvic fin rays, and sagittal otoliths for ageing two nonnative game species (Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta) and one native trout species (Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis) listed as a species of concern with the objective of finding a suitable nonlethal ageing structure.  To evaluate the suitability of the various ageing techniques, precision and relative accuracy of the estimated ages were compared for the three species.  Two independent readers, age bias plots, coefficients of variation, and percent agreement were used to measure bias among structures for each reader and precision between readers for each structure.  Relative accuracy was investigated by comparing mean otolith age estimates versus mean scale and fin ray estimates as well.  The ability to use nonlethal ageing structures for ageing would be beneficial for fisheries biologists trying to manage these trout populations.