Egg Deposition and Development of a Spawning Habitat Suitability Model for Lake Sturgeon (Acipenser fulvescens) below a Hydroelectric Dam on a Large River in the Precambrian Shield of Central Canada

We studied the pattern of egg deposition from a healthy population of Lake Sturgeon (Acipenser fulvescens) for five consecutive spawning periods below the hydroelectric dam at Pointe du Bois on the Winnipeg River, Manitoba, and developed a Habitat Suitability Index (HSI) model to estimate habitat availability over a wide range of discharge.

Lake Sturgeon adapted to the hydraulic habitat available each spawning period. Eggs were deposited below the powerhouse where flows were always present and also below the spillway when spill occurred (n = 11,975). Egg traps (n = 3,118) were set as far as 500 m downstream of the dam although most were deployed within 150 m. About 90% of the eggs were within 90 m of the dam. Depth average velocities most often ranged 0. 5 – 2.2 m/sec, and over a wide range of boulder/cobble and smooth bedrock substrates, and near the full range of depth (13.3 m).

A five variable HSI model was developed after analyses using a three variable model showed the areas of suitable habitat modeled grossly exaggerated the area occupied by eggs. Two novel constraint variables, “Direction” of flow and “Distance” from the dam markedly improved the agreement with the egg data.