In 2002 and 2003, the Bishops Falls hydroelectric generating facility on the Exploits River, insular Newfoundland, Canada, underwent extensive refurbishing including replacement of turbines and installation of a 'retrofitted' bypass and fish handling system. The effectiveness of this new bypass system has been assessed during the annual downstream run of wild Atlantic salmon smolt and kelt in smolt were radio tagged and released between June 9 and July 2, in the forebay of the hydro plant (19 releases) and one upstream (in-river) release. Fish guidance efficiency (FGE) of the system overall was 63% (123 of 195 fish) with 36 fish passing through the turbines, and six known mortalities. In 2004, between June 9 and July 2, a total of 358 smolt and 103 kelt were released in the forebay in 45 and 13 releases (n = 8 per release), respectively. The FGE of the system for smolt was 71.7% (257 of 358 fish) and for kelt was 92.3% (95 of 103 fish). In 2004, 96 tagged smolt passed through the turbines and 43 (44.8%) were detected at a downstream station confirming they had survived turbine passage, suggesting an overall survival of smolt passage of the Bishops Falls hydro facility in the order of 85%. A total of seven kelts (6.8%) passed through the turbines and were not detected 1.5 km downstream suggesting they did not survive turbine passage. Smolt spent on average 39.8 h in the forebay before exiting in 2003 and forebay residency averaged 26 h in 2004. In both years, most smolt selected their passage route, actively or passively, within the first 10 h with secondary peaks at 25-30 and 50-55 h, corresponding to evening passage in the second and third night, after release. Few smolt were bypassed or entrained into turbines during daylight hours. In both years turbine passed smolt spent more time in the forebay suggesting the longer fish reside in the forebay the greater the likelihood of turbine entrainment. Kelt were either bypassed or turbine entrained relatively quickly, within 2 h of release, and virtually all kelts were bypassed/turbine entrained during the hours of 18:00 and 01:00. These data on fish behavior and residency in the forebay will assist further refinement of operations of the bypass facility to optimize survival.

Government (Fisheries and Oceans Canada) and industry (Abitibi Consolidated Company of Canada) have been working cooperatively to protect and enhance wild Atlantic salmon populations on the Exploits River, insular Newfoundland, Canada. Since the mid-1960s, enhancement programmes and construction of fish passage facilities at natural and man-made barriers in the watershed have expanded the range and increased the returning adult population from 1200 fish (circa 1960) to 22,000 fish, on average. Since 1997, attention has been paid to improving passage and survival of downstream migrating smolts and kelts at two hydroelectric facilities at Grand FallsWindsor and Bishops Falls. At Grand Falls-Windsor a floating louver and bypass system was installed in a power canal and extensive biological, hydraulic, and modelling studies have been conducted to assess, modify, and optimize fish passage. At Bishops Falls, a retrofitted surface spill bypass system was installed in an existing spill gate and similar studies have been conducted to improve passage success. Studies have also been conducted on the upstream migrating adults at these facilities and associated fishways, using conventional and physiological telemetry, to assess tailrace attraction and residency, and the relative energy cost of upstream migration to bypass the hydro plants and fishways. This article reviews the results of these various studies to demonstrate how cooperative work has improved passage of anadromous salmon in coexistence with hydroelectric development.

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Growth and sea survival rates decreased with increasing smolt age, with survival being 12, 6, and 3% for 3+, 4+, and 5+ smolt, respectively. All spawning fish were grilse, which suggests that older smolt became large salmon and were thus more vulnerable to the commercial fishery. A density-dependent relationship was observed for 3+ smolt in their 1st yr of growth, but not for older smolt; younger smolt probably spend their juvenile life in a more productive but space-limiting part of the river. Variation between river-system environments may be responsible for the opposing results of studies on Atlantic salmon (Salmo salar) life history. Key words: Salmo salar, growth, sea survival, density dependence, first-year growth, age at smoltification

Otoliths of rainbow trout Oncorhynchus mykiss reared in marine cages were analyzed by laser ablation-inductively coupled plasma mass spectrometry to determine their Sr and Mg concentrations and by micro-Raman spectrometry to assess mineralogy. Analyses of transects from the core of the otolith to the growing edge (incorporating otolith material produced during freshwater hatchery and marine cage growth) revealed that these transects were composed of aragonite, vaterite, or both. The concentration of Sr varied significantly between mineral polymorphs and environments (hatchery or marine). In vaterite transects, Sr concentrations increased an average of 130 lg/g between freshwater hatchery growth and marine growth. This increase represents a near doubling of the Sr concentration in vaterite and made Sr a suitable indicator of a change in the environment as reflected in vaterite transects. In aragonite transects, Sr concentrations increased an average of 1,330 lg/g between hatchery and marine growth, which simplified the identification of the timing of marine transfer. The concentrations of Mg also varied significantly between mineral polymorphs, the difference in the average concentration between aragonite and vaterite being 1,179 lg/g. This allowed for the use of Mg as a proxy for mineralogy. While there was an increase in Mg concentration between hatchery and marine growth in some vaterite otoliths, the change was small compared with the change as a result of mineralogy. The average aragonite-vaterite partition coefficients were 5.238 and 8.096 for Sr and 0.057 and 0.128 for Mg for hatchery and marine growth, respectively.