Wild and farmed burbot Lota lota: differences in energy consumption and behavior during the spawning season

Abstract

Farmed fish released in a native environment can display different spawning behaviour compared to their wild conspecifics. In our study, farmed and wild burbot, a species recently introduced for aquacultural production, were equipped with electromyogram (EMG) radio tags. EMG biotelemetry allows a description of the spatial distribution of fish together with simultaneous measurements of individual energy consumption. Farmed burbot were released into the wild to simulate stocking or hatchery escape and were observed over a nocturnal phase during November to January. The observational period was assumed to cover the whole spawning season, including an expected peak of spawning activity determined according to egg production by naturally spawning burbot in an experimental seminatural river channel. We detected increased energy consumption and lower movement activity at the time of expected peak spawning for wild burbot only. Across the whole spawning season, farmed females showed lower movement activity and energy consumption than wild females, whereas the opposite results were found for farmed males. Farmed and wild fish kept larger distances between each other than the individuals within a group (farmed and wild) across the whole spawning season. The closest positions occurred between males and females in the wild group, while for farmed fish, the closest position was found within the same sex. Sexually conditioned energy consumption and spatial distribution differed between wild and farmed fish.