Modeling movements of lake charr eggs on spawning grounds

Because little is known about the effects of currents on lake charr (Salvelinus namaycush) deposition and fate of eggs, a method to determine their role in spawning success was developed. It is suggested that an ideal strategy for lake charr egg survival is to select hydrodynamic conditions that allow for eggs to roll on lakebed and into void spaces in the substratum, whilst avoiding to be lifted from it. On that basis, egg movement on spawning grounds were modeled using an approach that combines fluid mechanics and biology. Wave modeling combined with drag and lift forces and egg parameters were used to propose both critical entrainment and resuspension velocities as well as a modular range of depths that should be ideal for lake charr spawning given a certain fetch. Modeling suggested that critical velocities of 4.1 and 10.3 cm/s would cause egg entrainment and resuspension respectively. The model was partially validated using in situ sampling on three spawning sites in Lake Témiscouata (Québec, Canada). Then, further model applications were conducted on twelve characterized Great Lakes spawning sites using data found in the literature. Relation of egg survival and the difference between resuspension depth and spawning depth at those sites was found to fit y=66.78e0.13x with a correlation coefficient r2=0.89. The findings provide the first explanation of the impact of currents on lake charr spawning success. They provide insight to help researchers and authorities in their restorative and protection efforts for lake charr populations.