Research Document - 2008/015

Narrative description and quantification of the habitat requirements of Lake Sturgeon, Acipenser fulvescens in the Great Lakes and upper St. Lawrence River

By R.G. Randall

Abstract

Lake sturgeon, Acipenser fulvescens, that inhabit the Great Lakes and upper St. Lawrence River (DU8) are a large-bodied (100 to 140 cm TL), slow-growing, migratory species that require extensive habitat. Most populations spawn in high-gradient reaches of large rivers, often below obstructions, with current velocities of 0.5 to 1.3 m s^-1, water depths of 0.1 to 2 m, and coarse but variable substrate. A study in the St. Lawrence River indicated from 13 to 48 m² of spawning habitat was needed for optimal egg survival. Emergent fry move downstream with the river current. Young sturgeon grow rapidly in river habitat from a size at emergence of about 17-18 mm to 123 mm by September, feeding on a diverse fauna from the benthos and drift. Habitat preferences of young sturgeon are largely unknown. Survey catches in the St. Lawrence were highest in water depths of 3-6 m and currents ranging between 0.25–0.5 m s^-1. There is evidence that juveniles aggregate at localized areas in rivers, shallow river mouths or adjacent bays during late summer and fall, but are later found in the same habitats as adults after their first year. The habitat of adult lake sturgeon is the highly productive shoal areas of lakes and large rivers; most fishing captures were from about 5 to 9 m, but they are taken occasionally as deep as 43 m. Other studies indicate adults utilize deeper water depths during summer, but prefer shallower water (<9 m) in winter. Adult sturgeon feed on benthic fauna, often on silt or mud substrate. Mature sturgeon migrate considerable distances (138 to 225 km in the St. Lawrence River) to find suitable spawning habitat. Based on allometric relationships, individual area per adult sturgeon (100 cm TL) was estimated to be 0.05 and 0.15 ha, in rivers and lakes, respectively. Home ranges were estimated to be 20X larger. Despite these large area requirements, adult habitat is unlikely to be limiting to lake sturgeon in the Great Lakes. However, spawning habitat may be limiting for certain populations, because of dams, habitat fragmentation, habitat degradation, or lack of access to spawning habitat. Future research should focus on the quality and quantity of spawning and juvenile habitat of individual populations of lake sturgeon, and confirm that adult habitat is not limiting in the Great Lakes and upper St. Lawrence River.

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