Project
Effects of thiaminase and lipids on Thiamine Deficiency Complex (TDC) in lake trout
RATIONALE: A proposed barrier to the re-establishment of lake trout (Salvelinus namaycush), one of the few remaining native deep-water fishes in the Great Lakes, is the abundance of non-native prey fishes. Rainbow smelt (Osmerus mordax) and alewife (Alosa pseduoharengus) are two non-native prey species known to contain high levels of thiaminase, an enzyme which can cause Thiamine Deficiency Complex (TDC) in salmonines. An alternative hypothesis proposes that diets rich in lipids causes TDC in salmonines. Few studies on salmonines in the Great Lakes have been able to differentiate the effects of thiaminase versus lipids on TDC, even though the prey base in the Great Lakes differ in both elements. Furthermore, lake trout strains that are available for reintroduction programs may differ in their resilience to diets high in thiaminase and lipids, so an assessment of any resilience is also warranted to direct strain selection.\\r\\nOBJECTIVES: We will formulate diets that differ in thiaminase and lipid content and then assess the effects of the diets over a 9 month experiment on tissue thiamine levels, growth, swimming performance, skin colour, and survival of fish from three strains of lake trout available for reintroduction efforts. These pilot results will assess if a larger and longer scale study involving diets that differ in both thiaminase and lipids is warranted to fully assess the effects of diet and differences among strains in resilience to high thiaminase and/or lipids. Our study will also determine if an easily assessed biomarker is available to assess TDC in lake trout.\\r\\nMETHODS: We will obtain juvenile lake trout from the Lake Manitou, Seneca Lake, and Michipicoten strains. Juvenile lake trout will be transferred to the hatchery facility at the University of Windsor where the fish will be housed in groups of four tanks representing separate strains to create a 2×2 factorial feeding experiment. The tanks will be randomly assigned one of four diets: (1) high thiaminase, high lipids; (2) high thiaminase, low lipids; (3) low thiaminase, high lipids; or (4) low thiaminase, low lipids (control). Commencing 9 months post initiation of the experimental diets, performance traits including thiamine and lipid tissue concentration, growth, swimming performance, skin colouration, and survival will be quantified. \\r\\nRELEVANCE TO PROGRAM: This pilot proposal is being submitted under the Re-establishment of Native Deepwater Fish theme area. We will compare thiamine levels between three strains of lake trout which addresses the Lake Ontario research priority to identify differences in thiamine levels among lake trout stains. This research will directly address the question from the theme paper: what are the limiting factors and causes leading to reduced or lost recruitment of desired fish species and what are the solutions to remedy this lost recruitment? We will assess effects of both thiaminase and lipids on TDC performance of three strains of lake trout and any potential differences in resilience among strains.\\r\\nDELIVERABLES AND DISTRIBUTION OF FINDINGS: We will develop new diet formulations that differ in thiaminase and lipids to provide one of the first studies that examine both effects on TDC in salmonines. We will also assess potential effects of the diets on thiamine levels and performance of lake trout from three strains that are available for reintroduction into the Great Lakes. These initial data will inform if a third strain (from Lake Manitou) should also be used in Great Lakes reintroductions, as well as inform the management of prey base based on thiaminase and lipid content. We plan to publish several papers, present at conferences and stakeholder engagements, and work with our partners to inform policy decisions.