Morphological variation of siscowet lake trout in Lake Superior

Transactions of the American Fisheries Society
By:  and 



Historically, Lake Superior has contained many morphologically distinct forms of the lake trout Salvelinus namaycush that have occupied specific depths and locations and spawned at specific times of the year. Today, as was probably the case historically, the siscowet morphotype is the most abundant. Recent interest in harvesting siscowets to extract oil containing omega-3 fatty acids will require additional knowledge of the biology and stock structure of these lightly exploited populations. The objective of this study was to determine whether shape differences exist among siscowet populations across Lake Superior and whether these shape differences can be used to infer stock structure. Morphometric analysis (truss protocol) was used to differentiate among siscowets sampled from 23 locations in Lake Superior. We analyzed 31 distance measurements among 14 anatomical landmarks taken from digital images of fish recorded in the field. Cluster analysis of size-corrected data separated fish into three geographic groups: The Isle Royale, eastern (Michigan), and western regions (Michigan). Finer scales of stock structure were also suggested. Discriminant function analysis demonstrated that head measurements contributed to most of the observed variation. Cross-validation classification rates indicated that 67–71% of individual fish were correctly classified to their region of capture. This is the first study to present shape differences associated with location within a lake trout morphotype in Lake Superior.

Publication type Article
Publication Subtype Journal Article
Title Morphological variation of siscowet lake trout in Lake Superior
Series title Transactions of the American Fisheries Society
DOI 10.1577/T06-098.1
Volume 136
Issue 2
Year Published 2007
Language English
Publisher Taylor & Francis
Contributing office(s) Great Lakes Science Center
Description 9 p.
First page 509
Last page 517
Online Only (Y/N) N
Additional Online Files (Y/N) N
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