FISHERIES - SALMON REDDS |
Spawning salmon are less likely to access spawning grounds higher in the Frome catchment when there is insufficient water in the river. © Laurie Campbell
ACKNOWLEDGEMENTS
We would like to thank Nicole Caetano and Andy Martin of the UK Environment Agency, the Frome, Piddle and West Dorset Fishing Association, the Weld Estate and Casterbridge Fisheries Ltd. This work was part-funded through an EU Knowledge Exchange Skills Scholarships grant awarded to Elinor Parry.
Therefore it seems that adult salmon tend to spawn within the middle of the
river reaches under drought conditions. Perhaps they are aggregating under potential barriers, such as weirs, or perhaps some areas of the river, such as the lower reaches, tributaries and upper reaches, are too shallow for spawning. Under extreme high flows, low numbers of redds are found throughout the river. Although this may be due to the difficulty in locating redds under high flow, it is also possible that sedimentation and rough water may cause problems for salmon attempting to spawn in the river. Salmon may struggle to bounce back from their current decline, as climate change predictions suggest that drought and flood events will increase over the next century. Understanding how flow is affecting salmon spawning behaviour will enable us to act to aid the species recovery. Improved access to upper reaches through carefully managed abstraction regimes, collaborating with farmers to reduce sedimentation and further improvements to our rivers will help to curb the effects of future climate change on this incredible migratory fish. This study and its recommendations are now published in the international peer-
reviewed scientific journal Ecology of Freshwater Fish
http://onlinelibrary.wiley.com/ doi/10.1111/eff.12330/abstract.
Increasing mean daily flow
Figure 1
Plots showing redd densities against standard- ised distance from the tidal limit. Each panel represents a different year characterised by a measure of mean daily flow from 1 October to 31 December, and panels are ordered from low (top left) to high (bottom right) flow. Lines are the ‘top-ranked’ model fits. As flow and distance were standardised, no units are specified for these variables
Standardised distance
www.gwct.org.uk GAME & WILDLIFE REVIEW 2016 | 17
Observed redd density (per km)
Increasing mean daily flow
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