Redds in space

Elinor Parry did her MSc thesis with the GWCT Fisheries Team from February to August 2015 on the effect of flow on the distribution of salmon redds in the Frome.

Map of the river Frome, Dorset, UK, showing the redd survey sections analysed.

Elinor found that flow effects salmon redd distribution in ways that she predicted: redds were more aggregated in the mid-river in years of low flow compared to years of high flow. This suggests that spawning salmon have difficultly accessing spawning grounds higher in the Frome catchment when there is insufficient water in the river between October and January.

Diagram showing how the density of redds is predicted to change with distance from the tidal limit under low, medium and high flow conditions.

There are important management implications from Elinor’s study, particularly in light of the forecast increase in frequency and intensity of extreme floods and droughts under climate change and forecast increases in the Dorset human population size. Her findings suggest that we should manage water levels sensitively, particularly between October and January, to ensure that salmon can distribute their redds throughout all of the available spawning habitat, which will give the emerging fry the best chance of survival.

Elinor’s study was very challenging. Among the many difficulties she had to overcome, three were particularly prominent:

1. She had the arduous task of collating incomplete and inconsistent datasets into a single manageable database that she could use to test her predictions;
2. She had the near impossible task of deciding how to summarise river discharge data in a way relevant to salmon spawning migrations on the Frome; and
3. She had to devise a statistical analysis to describe salmon redd distributions using only a few simple explanatory variables.

In completing these tasks, Elinor demonstrated great care, attention to detail, innovative thinking and an ability to critically appraise literature and information.

Her MSc project will soon be published in the Ecology of Freshwater Fish.

She submitted her thesis to the Cardiff University School of Biosciences in September and was awarded a well-earned Distinction – congratulations Elinor!

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Citation

BibTeX citation:

@online{d. gregory2016,
  author = {D. Gregory, Stephen},
  title = {Redds in Space},
  date = {2016-09-01},
  url = {https://stephendavidgregory.github.io/posts/elinor},
  langid = {en}
}

For attribution, please cite this work as:

D. Gregory, Stephen. 2016. “Redds in Space.” September 1, 2016. https://stephendavidgregory.github.io/posts/elinor.