Comparative Bioenergetics of Two Lake Trout Morphotypes
Open Access
- Author:
- Schall, Megan Victoria
- Graduate Program:
- Wildlife and Fisheries Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 08, 2013
- Committee Members:
- Tyler Wagner, Thesis Advisor/Co-Advisor
- Keywords:
- bioenergetics modeling
lake trout
Bayesian inference - Abstract:
- Lake trout (Salvelinus namaycush) are deep water apex predators native to North America that inhabit glacially formed lakes, including the Laurentian Great Lakes. Lake trout populations in the Great Lakes are recovering from overfishing, sea lamprey parasitism, and poor water quality conditions that occurred during the 19th and 20th centuries, in addition to present day stressors (e.g., invasive species, climate change, etc.). Current stocking and management strategies aim to produce self-sustaining and viable populations. Management is complicated, however, by the presence of multiple body forms (i.e., morphotypes) of lake trout which differ in habitat utilization, prey consumption, lipid storage, and spawning preferences. Bioenergetics models are useful management tools that relate fish physiology to habitat usage (e.g., prey consumed or growth predictions at a given temperature). However, there is currently only a single bioenergetics model developed for one lake trout morphotype (lean), and this model failed to incorporate temperatures outside lake trout’s preferred range. To investigate potential morphotype differences and develop bioenergetics models with broader temperature applications, I completed consumption and respiration experiments on two actively stocked lake trout morphotypes, lean and humper, across a wide range of temperatures (4-22°C) and size classes (5-100g). Bayesian estimation was used during model development to propagate uncertainty through to final growth predictions. Morphotype differences were minimal, but when present, were temperature and weight dependent. Basal respiration did not differ among the morphotypes at any temperature or size class tested. Growth and consumption differences were subtle and not consistent across size ranges tested. Management scenarios investigated (e.g., predicted growth at an average temperature of 11.7°C and 14.4°C over a 30 day period) demonstrated no differences in growth between the two morphotypes utilizing temperatures presently found in the Great Lakes. Yet, management decisions should not be based on energetics alone as other factors including available habitat, prey resources, and competition should also be considered. Managers should consider the characteristics of both the population structure and habitat conditions when developing recommendations for management of lake trout morphotypes.