Diel bank migration of Burbot (Lota lota)

Abstract

Determining the habitat use and movements by fish is critical to our understanding of aquatic ecosystem function. The objective of this study was to assess the diel movements of Burbot (Lota lota) over the open water season. We employed a high-resolution acoustic telemetry positioning system to track the movements and activity of four Burbot during the ice-free season (between June and September) in a sub-Arctic lake. Burbot underwent diel bank migration (DBM), a benthic form of diel vertical migration, where depths are transitioned in close association with the bottom rather than through the water column. During daytime, Burbot occupied deeper water, at the transition of soft, low complexity substrates and ascended along the rocky bottom lake banks to shallower water habitats at night. Increased activity rates during shallow water forays suggest active feeding events. DBM was low at the start of summer with nearly 24 h of daylight, but increased towards the mid-summer with a more pronounced night cycle, coalescing towards the fall. The DBM of Burbot is dynamic, with proximate triggers of light and temperature, and ultimate causes likely being foraging opportunities, bioenergetics gain and predator avoidance.