An Age Comparison Study: Using the Maxilla as an Alternative Age Determination Method for Lake Michigan Lake Trout, Salvelinus namaycush

Abstract

The understanding of fish population dynamics is essential to conservation efforts and the regulation of fishing for individual species. The capture of lake trout (Salvelinus namaycushWalbaum) and the extraction of calcified structures for age determination are necessary to study changes in the species’ populations within the Great Lakes. There are two structures, scales and otoliths, which are widely used for age determination. However, it is well known among fish biologists that scales are largely inaccurate at determining ages in older fish. Studies show that the otolith is the most precise structure for determining age, although it is quite difficult to read and years of experience are required to achieve accurate readings. A recent study discovered that thin sections of the maxillary bone, or upper jaw, proved to be much easier to read and just as accurate as the otolith for assessing fish age. This study was conducted to further solidify these findings by comparing ages obtained from scales, otoliths, and maxillae to the true age of the fish from which they were taken in order to ensure accuracy of age determination.