The onset of downstream movement of juvenile Atlantic salmon, Salmo salar L., in a chalk stream

Abstract

The downstream movements of wild Atlantic salmon, Salmo salar L., from their established feeding territories in the River Itchen, Hampshire, UK, were logged continuously over an 11‐month period using a passive integrated transponder (PIT) antenna system. The time of these movements was then related to a number of monitored and calculated environmental parameters. Initial downstream movement of smolts in April was correlated with the onset of darkness, at which time salmon moved from their established feeding territories alone. No relationship was found between the number of smolts migrating and river flow or maximum daily water temperature. The timing of downstream movement of parr between October and March was random with regard to sunset and time of maximum daily water temperature, suggesting the environmental cue that initiates movement may be different outside the spring smolt period.

Some observations on the impact of temperature and low flow on the onset of downstream movement of wild Atlantic salmon, Salmo salar L., smolts

“…Passive integrated transponder (PIT) antenna systems (Wyre Micro Design Ltd, Lancashire, UK) were installed in pairs at each exit to continuously monitor the movement of PIT-tagged fish into, or out of, the stream. A full description of this experimental facility can be found in Riley (2007) and Riley et al (2002Riley et al ( , 2006.…”

Social Recognition of Conspecifics

“…Nevertheless there is a clear difference in spacing between related and unrelated fishes. Perhaps this can be explained by work that suggests smolt migration occurs in two phases, beginning with solitary movement, followed by schooling as singletons join together (Bakshtanskiy et al 1980(Bakshtanskiy et al , 1988Wood et al 1993;Riley et al 2002). The smolts in Olsén's study may have been in the process of forming shoals, where the role of environment cues and habitat conditions may be of greater importance than kin-biased behaviour (Olsson et al 2006), and the intriguing possibility remains that the effect of kinship on shoal composition strengthens as migration proceeds.…”

Habitat Requirements for Juvenile Salmonids in Chalk Streams: How will Management Best Address Conflicting Interests?

“…The studies were carried out on three carriers of the River Itchen, a groundwaterfed chalk stream that drains a catchment area of 400 km 2 in southern England and has a stable discharge of clear alkaline water with a relatively stable temperature regime (Riley et al 2002, Riley et al 2006. Each carrier flows from a single, controllable, sluice gate on the Itchen Navigation Canal to the main River Itchen near Winchester (Figure 12.1).…”

“…Each summer, the salmon and trout from the study site in the Brandy stream, and immediately downstream, were scanned for the presence of a Passive Integrated Transponder (PIT) tag, and those without a tag (usually 0+ groups) were PIT tagged and had their adipose fin clipped (Riley et al 2002).…”

“…The movements of PIT-tagged fish into and out of the Brandy stream study site were recorded by permanently fixed antennae systems (Wyre Micro Design Ltd, Lancashire, UK: Riley et al 2002) installed at the three outlets. Fish movement upstream into the Navigation Canal is considered to be unlikely due to the force of water passing through the undershot sluice (Riley et al 2003).…”