Morphological and trophic differentiation of growth morphotypes of walleye (Sander vitreus) from Lake Winnipeg, Canada

Thumbnail Image
File version
Moles, MD
Robinson, BW
Johnston, TA
Cunjak, RA
Jardine, TD
Casselman, JM
Leggett, WC
Griffith University Author(s)
Primary Supervisor
Other Supervisors

257825 bytes

File type(s)



Ecologically related polymorphisms occur in many northern freshwater fish populations and are distinguished by alternate phenotypes consistently associated with differential use of habitats or resources. We tested for polymorphism in walleye (Sander vitreus (Mitchill, 1818)) in the south basin of Lake Winnipeg, where evidence suggests that "dwarf" and "normal" growth forms may coexist. Morphometric comparisons of these growth forms at similar size demonstrated significant differences in the relative sizes of head, snout, eye, and mouth, collectively suggesting dwarf individuals inhabit a more benthic niche than normal morphs. Stable isotope analysis did not support this morphometric interpretation, however, as d13C and d15N isotope signatures were similar between similar-sized individuals of both forms, but differed from those of large normal walleye. Walleye from Lake Winnipeg do not seem to exhibit a simple resource polymorphism where different ecotypes are associated with alternate habitats throughout their life history, nor do they exhibit characteristics of a simple mating polymorphism. We suggest the walleye from Lake Winnipeg represent two growth forms sharing a common juvenile habitat followed by the normal form shifting into an alternative adult niche. Des polymorphismes de nature 飯logique se produisent dans plusieurs populations bor顬es de poissons d'eau douce et se caract鲩sent par le fait que les diff鲥nts ph鮯types sont associ鳠࠵ne utilisation particuli貥 des habitats ou des ressources. Nous avons v鲩fi頬e polymorphisme chez le dor頨Sander vitreus (Mitchill, 1818)) dans le bassin sud du lac Winnipeg, o頩l y a des indications de coexistence de formes de croissance 렮aines 력t 렮ormales 뮠Des comparaisons morphom鴲iques de ces formes de croissance ࠤes tailles semblables montrent des diff鲥nces significatives dans les tailles relatives de la t괥, du museau, de l'쩬 et de la bouche qui, consid鲩es conjointement, laissent croire que les individus nains occupent une niche plus benthique que les individus normaux. Une analyse des isotopes stables n'appuie, cependant, pas cette interpr鴡tion morphom鴲ique puisque les signatures isotopiques d13C et d15N sont semblables chez les individus de mꭥ taille des deux formes, mais elles diff貥nt de celles des dor鳠normaux de grande taille. Les dor鳠du lac Winnipeg ne semblent pas poss餥r un simple polymorphisme des ressources dans lequel les diff鲥nts 飯types sont associ鳠ࠤes habitats diff鲥nts pendant tout leur cycle biologique; ils n'ont pas non plus les caract鲩stiques d'un simple polymorphisme d'accouplement. Nous croyons que les dor鳠du lac Winnipeg comprennent deux formes de croissance qui partagent un habitat commun durant leur p鲩ode juv鮩le et qu'ensuite la forme normale va occuper une niche adulte diff鲥nte.

Journal Title

Canadian Journal of Zoology

Conference Title
Book Title




Thesis Type
Degree Program
Publisher link
Patent number
Grant identifier(s)
Rights Statement
Rights Statement

© 2010 NRC Research Press. The attached file is reproduced here in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitive, published version.

Item Access Status
Access the data
Related item(s)


Freshwater ecology


Persistent link to this record