Influence of body condition on the population dynamics of Atlantic salmon with consideration of the potential impact of sea lice

R Susdorf, N K G Salama, D Lusseau

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12 Citations (Scopus)
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Atlantic salmon Salmo salar is an iconic species of high conservation and economic importance. At sea, individuals typically are subject to sea lice infestation, which can have detrimental effects on their host. Over recent decades, the body condition and marine survival in NE Atlantic stocks have generally decreased, reflected in fewer adults returning to rivers, which is partly attributable to sea lice. We developed a deterministic stage-structured population model to assess condition-mediated population dynamics resulting in changing fecundity, age at sexual maturation and marine survival rate. The model is parameterized using data from the North Esk system, north-east Scotland. Both constant and density-dependent juvenile survival rates are considered. We show that even small sea lice-mediated changes in mean body condition of MSW can cause substantial population declines, whereas 1SW condition is less influential. Density dependence alleviates the condition-mediated population effect. The resilience of the population to demographic perturbations declines as adult condition is reduced. Indirect demographic changes in salmonid life-history traits (e.g., body condition) are often considered unimportant for population trajectory. The model shows that Atlantic salmon population dynamics can be highly responsive to sea lice-mediated effects on adult body condition, thus highlighting the importance of non-lethal parasitic long-term effects.

Original languageEnglish
Pages (from-to)941-951
Number of pages11
JournalJournal of Fish Diseases
Issue number6
Early online date21 Nov 2017
Publication statusPublished - Jun 2018

Bibliographical note

We thank Marine Scotland Science (MSS) for providing the studentship for this work. We are grateful to Alexander G Murray from MSS Aberdeen for providing data for model parameterization. We also want to thank Gordon Smith and Ian Simpson from MSS Montrose, as well as the owner and staff of the net fishery at North Esk for enabling data collection. We thank Peerage of Science and two anonymous referees for constructive comments and critique points which considerably improved earlier drafts.


  • Journal Article
  • Atlantic salmon
  • matrix model
  • non-lethal effect
  • population dynamics
  • sea lice
  • stage-structured population


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