Deregulation of the electric power market globally will lead to increased requirement for electricity on demand resulting in more emphasis on 'hydropeaking' generation. A research study was conducted on the regulated West Salmon River, Newfoundland, Canada, to examine habitat selection and movement of juvenile Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis) in response to flow changes related to 'experimental' peaking flow power generation. Fish were surgically implanted with microscale radio transmitters, released into an experimental study, and discharge was experimentally manipulated simulating two scenarios: (i) water storage during the day and generation at night, with a 2 hour transition; and (ii) night-time storage with generation during the day. Experiments were repeated in the summer and fall. Fish were tracked throughout the diurnal cycle of each manipulation and precisely positioned in two-dimensional space. Atlantic salmon exhibited two distinct patterns to movement: fish that showed high site fidelity and those that moved considerably during trials. Both salmon and trout were more active during fall hydropeaking experiments. Fish generally did not move long distances and moved more in a longitudinal fashion than laterally. Salmon moved greater distances, on average, than trout under all experimental conditions and during both seasons but these differences were not statistically significant. Brook trout moved more in relation to dynamic events (up-and down-ramping) than at steady state flows. Trout also moved more at night during these dynamic changes and under low flow conditions. These results will assist producers of hydroelectricity to reduce the impacts of hydropeaking operations on fish and fish habitat.

Information on estuary-dependence of bass in U.K. waters is summarized from recent published reports and some unpublished data.There is substantial reliance on estuaries (including tidal backwaters with little freshwater inflow) such as the Hampshire harbours, in the first 4-5 years of life. Man-related hazards to survival are considerable and increasing: they include destruction of or damage to habitats, losses of0-groups in power-station intakes, and excessive unregulated fishingeffort, mainly on 4-5-yearold bass. Some measures to protect bass in estuaries are now in hand, but much remains to be done.

Tagging data for 5959 bass, Dicentrarchus labrax L., released around England and Wales between 1970 and 1984 have been compiled and analysed to show seasonal distribution patterns and implied movements of populations in the southern North Sea, the central English Channel and the south-west and west coasts. Juvenile bass appear to remain near their nursery areas throughout the year, whilst adults show extensive migrations between summer feeding areas and winter pre-spawning areas, which are specific to local populations. Straying occasionally occurs between populations, but only at the ‘adolescent’ phase, and for management purposes local populations may be considered discrete.

A bass tagging project on the south coast of Anglesey, 1971–5, yielded 86 recoveries from 912 taggings. In addition to expected local movements a systematic pattern of seasonal migration was identified for adults. Fish present in summer moved to south Cornwall for the winter, returning in succeeding summers for spawning. Departure was normally before mid-October. Fish present after that had summered further north (reaching Furness in warm summers). These too moved south as winter advanced, though possibly not reaching Cornwall. A few solitary fish – unfit specimens or members of weak year-classes – appeared to remain through the winter. No evidence was found of movement to, or intermingling with stocks of, the Irish coast; nor, with one exception, the mainland coast of Europe. There was also no indication of movement eastward along the south coast: suggesting discrete populations there from those on the west coast.

INTRODUCTIONPresence of O-group bass, Dicentrarchus labrax (L.), has been recorded for a number of estuaries and tidal backwaters in the south of the United Kingdom, including the tidal Thames (Wheeler, 1979), the outer Thames at Southend (Murie, 1903), the Medway (Van den Broek, 1979), Langstone Harbour (Reay, 1973), the Dart (Dando & Demir, 1985), and the Tamar (Hartley, 1940). The author has found them, additionally, in Chichester Harbour and in the Cuckmere (Sussex), Teign and Tavy estuaries. Correspondents have reported them from the estuaries of the Blackwater (Cox), Crouch (Wiggins), Lynher (Gee) and Fal (Melhuish); also from the Fleet backwater in Dorset (Fear). It may be inferred that all estuaries and tidal backwaters on the south and south-east coasts of the U.K. constitute bass nurseries, in some degree.*