Growth and Annulus Formation in Young-of-the-Year Rainbow Trout in Great Smoky Mountains National Park

Delashmit, Amy

Honors Thesis: ABSTRACT: Age and growth studies of rainbow trout (Oncorynchus mykiss) have traditionally focused primarily on fish in the northeastern United States. Little research has been completed on trout at the southern margin of their distributions. This study was an attempt to determine (1) growth patterns, (2) time of annulus formation in scales and otoliths and their relations to growth patterns, and (3) percent agreement between scale age and otolith age in young-of-the-year (YOY) rainbow trout in Great Smoky Mountains National Park. Young-of-the-year rainbow trout were sampled monthly from September 1996 to Septernber 1997. Total lengths and weights were recorded, and scales and otoliths were collected for analysis. Growth between March and June (spring) was significantly greater than other times of the year. Condition peaked in March at the beginning of this growth period. Annuli were observed on scales in March and April while annuli appeared on otoliths in April. Mean agreement between scales and otoliths for the study was 93.7%. These results suggest that rainbow trout in the southern Appalachians do not follow the growth patterns observed in other parts of the country; the majority of growth occurs in the spring, and there is little growth during the remainder of the year. This study and further examination of age and growth in the Southeast will provide fisheries biologists better information with which to make management decisions.