Native Trout Program - Bull Trout Age Analysis
Recovery
of bull trout listed as threatened under the Endangered Species Act
will depend on assessing the status of populations. To conduct an
adequate assessment, it is necessary to determine the age structure
of various populations or metapopulations. The age of most salmonids
has been determined using a variety of methods. Scales may be collected
non-lethally, analyzed relatively inexpensively, and for many salmonids
provide sufficiently accurate age information. However, bull trout
are a member of the charr family (Salvelinus spp.). Scale analysis
of charr often provides relatively inaccurate age information. Fin
rays may be used to determine the age of bull trout, may possibly
be collected non-lethally, and are only moderately expensive to analyze.
Otolith analysis provides very accurate age information but otoliths
are collected through lethal sampling and analysis is relatively expensive.
The purpose of this study is to provide additional guidance toward
methods of determining age in bull trout. The primary objective is
to compare accuracy of age analysis using scales, fin rays, and otoliths
from known age bull trout. The ultimate goal of this project is to
determine age structure of bull trout populations using non-lethal
means.
