To study quantitatively the relationship between immigration rate and gene flow we used 9‐year data from a willow tit Parus montanus population in a continuous forest habitat. We compared components of lifetime reproductive success, and parental survival rate between immigrant and resident (‘status’) birds by taking individual age into consideration also. Of the fitness components, survival was independent of status and sex, averaging 0.60 annually. Of the male and female breeders, on average 63.1% and 75.6%, respectively, originated from unknown natal areas, implying extensive immigration. Pair formation was nonassortative with respect to the origin of partners. The effect of status on reproductive success was significant only for females: immigrants produced larger clutches and hatched more young in all age classes studied. However, the difference between the groups diminished until fledging and the offspring produced by the immigrant females showed lower local survival rate (4.6% of the young) than did those by the residents (5.9%). Therefore, the contribution of immigrant females to the local gene pool was lower than expected on the basis of immigration rate. However, we propose that the result implies differential propensities to long‐distance dispersal rather than overall survival prospects, since we detected no quality differences suggesting reduced survival chances among descendants of immigrant females. Therefore, gene flow into the population was slightly lower than immigration rate. It is possible that immigrant females are more prone to invest in progeny that effectively disperse further to search for new vacancies. The conditions prevailing during nestling growth may be crucial in determining whether an individual will later become a resident or leave the natal area, but the genetic component of this trait should also be considered. We suggest that widespread propagules is a better strategy than philopatry for a short‐lived species to minimize the risk of losing all descendants in temporally and spatially varying conditions.

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Movements and habitat use by pikeperch (Stizostedion lucioperca (L.)) in a hydropeaking reservoir Un resumen en espanÄ ol se incluye detra s del texto principal de este artõ culo.Abstract ± We used radio telemetry to measure the habitat use and movements of 20 tagged pikeperch (44±59 cm) in the hydropeaking PyhaÈ koski Reservoir, Finland, during June 1999±2000. The hydrological conditions in the 8-km-long reservoir were measured and then modeled over eight discharge rates between 30 and 700 m 3 Á s À1 . Pikeperch preferred relatively low water velocities and deep water depths especially during the winter. During the summer, pikeperch moved actively in different parts of the reservoir. No relationship was found between hydroelectric plant operations and distances moved by pikeperch during the summer. Movements peaked in autumn but decreased during the winter to a restricted area. After 1 year of monitoring, 4 out of 20 tagged pikeperch remained in the PyhaÈ koski Reservoir, three had died when descending from hydroelectric dams, 10 had descended downstream to other reservoirs or sea, two were captured by local fishermen, and one fish's signal was lost for unknown reasons.

Summary This paper describes a case study to rehabilitate habitat for adult European grayling (Thymallus thymallus L.) in a large river reservoir in northern Finland. A channelled river reach was restored by building small islands and reefs as well as cobble and boulder structures for grayling. The total area of the restored stretch was 1.0 ha. The physical habitat was mapped using an echosounder, Doppler device, tachometer and scuba diving, and modelled with a 2D hydraulic model. The mean water velocity in the modelled stream section was 0.28 m s−1 during 110 m3 s−1 flow and 0.43 m s−1 during 300 m3 s−1 flow. Twelve adult grayling, tagged with transmitters, were released into the area and tracked for a maximum period of 30 days. The grayling largely stayed in the restored area and tended to avoid the unchanged channel of the river. The range of daily movement was from stationary to 2700 m per day. The adult grayling preferred water velocities between 0.20 and 0.45 m s−1, water depths between 0.20 and 1.55 m and coarse substrate. The study provides a small part of the information needed in habitat restoration for grayling.

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