–  Ultrasonic telemetry and hydrodynamic modelling were used to study the migratory behaviour of 54 wild Atlantic salmon (Salmo salar) smolt captured in freshwater during their downstream migration and tracked in 2 years through a shallow estuary system. A high‐density, fixed array of receivers provided detailed spatial and temporal resolution of behaviour in the second year of study. Smolt migration in the river occurred mostly at night and downstream migration was slower during the day. In the estuary, smolt moved seaward on ebbing tides and landward on flooding tides. The effect of current velocity was greater during the night than during the day. We documented for the first time that current velocity and diurnal period only accounted for approximately one‐third of the variation in smolt ground speeds in the estuary, indicating that smolt movements were far less passive than previously reported. Smolt energetic status had no effect on smolt swimming behaviour or migratory performance. With an increase in salinity, smolt seaward movements during flooding tides were more frequent, and overall seaward ground velocity increased. The increase in salinity experienced by the smolt during their migration through the leading edge of saltwater intrusion thus induced a behavioural transition from a more passive, fluvial migration to a more active‐ and seaward‐oriented migration.

Migration patterns of wild Atlantic salmon Salmo salar smolt were examined in a coastal embayment in the Gaspé peninsula of Québec, Canada. Twenty-four smolt in 2005 and 30 in 2006 were tagged with coded ultrasonic transmitters, and their migration throughout the bay was monitored using an array of fixed VR2 hydrophone receivers. Migration patterns were complex, with some smolt taking a direct route through the coastal embayment and others repeatedly changing direction over short spatial and temporal scales. Migration was mainly an active process with an overall outward (seaward) migration in the face of an inward residual circulation. Swimming direction was mainly outward during nocturnal inflowing currents but was more dispersed during daytime and nocturnal outflowing currents; swimming speed was greater during daytime than during nighttime. This pattern was consistent with smolt migrating offshore nocturnally and using daytime for prey detection and predator avoidance. Salinity had a strong effect: exposure to more saline waters caused increased swimming speeds. These observations are consistent with the hypothesis that smolt exploit an innate compass to maintain a preferred bearing and that the speed and direction of swimming is controlled by salinity and the diurnal cycle.

Hedger, R. D., Martin, F., Dodson, J, J., Hatin, D., Caron, F., and Whoriskey, F. G. 2008. The optimized interpolation of fish positions and speeds in an array of fixed acoustic receivers. – ICES Journal of Marine Science, 65: 1248–1259. The principal method for interpolating the positions and speeds of tagged fish within an array of fixed acoustic receivers is the weighted-mean method, which uses a box-kernel estimator, one of the simplest smoothing options available. This study aimed to determine the relative error of alternative, non-parametric regression methods for estimating these parameters. It was achieved by predicting the positions and speeds of three paths made through a dense array of fixed acoustic receivers within a coastal embayment (Gaspé Bay, Québec, Canada) by a boat with a GPS trailing an ultrasonic transmitter. Transmitter positions and speeds were estimated from the receiver data using kernel estimators, with box and normal kernels and the kernel size determined arbitrarily, and by several non-parametric methods, i.e. a kernel estimator, a smoothing spline, and local polynomial regression, with the kernel size or smoothing span determined by cross-validation. Prediction error of the kernel estimator was highly dependent upon kernel size, and a normal kernel produced less error than the box kernel. Of the methods using cross-validation, local polynomial regression produced least error, suggesting it as the optimal method for interpolation. Prediction error was also strongly dependent on array density. The local polynomial regression method was used to determine the movement patterns of a sample of tagged Atlantic salmon (Salmo salar) smolt and kelt, and American eel (Anguilla rostrata). Analysis of the estimates from local polynomial regression suggested that this was a suitable method for monitoring patterns of fish movement.

Factors influencing the migration and swimming depth of Atlantic salmon kelts Salmo salar L. within the York Estuary and Gaspé Bay (Québec, Canada), and in the Gulf of St. Lawrence between Gaspé Bay and the Strait of Belle Isle (Newfoundland, Canada) were studied using acoustic telemetry. In 2006 and 2007, a total of 49 kelts were tagged with acoustic transmitters equipped with depth sensors, released in the river delta leading into the estuary, and tracked using a fixed receiver array within the estuary and the bay. A large variation in migratory behavior existed, with some kelts making a direct, strongly oriented traverse across the estuary and bay, and others showing multiple changes in orientation. There was long-term residence (typically several weeks) in the river delta and rapid migration once kelts reached the estuary and bay resulting from seaward swimming, with a net seaward movement even on a flood tide. Diving was more frequent during daytime. It was hypothesized that diving may have been related to feeding and/or the identification of more temporally consistent sub-surface salinity gradients or current flow directions. The patterns of migration within the coastal zone were similar to those identified for smolts, implying a universal pattern of coastal zone migratory behavior in both smolts and kelts. Migration speed within the marine habitat was dependent on date of departure from Gaspé Bay, which in turn was dependent on the length of time kelts had remained in the delta. It was hypothesized that extended feeding within the delta allowed kelts to improve their physical condition, enabling them to migrate more rapidly in the marine habitat.

On construit la théorie des périodes pour les formes modulaires de poids 1, qui étend la théorie classique pour les formes de poids supérieur, et la théorie des périodes pour les formes de Maass. On transporte les structures usuelles sur les formes modulaires dans l'espace des périodes (produit scalaire de Petersson, opérateurs de Hecke). On donne une interprétation cohomologique de l'isomorphisme de périodes, et on étend la construction des périodes aux formes non paraboliques. Enfin, on montre que la période d'une forme modulaire f est déterminée par les valeurs aux entiers négatifs des fonctions L tordues par des symboles modulaires, ce qui permet de reconstruire f à partir de ces valeurs.