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Landscape Ecology

, Volume 32, Issue 10, pp 1953–1967 | Cite as

Network analysis reveals strong seasonality in the dispersal of a marine parasite and identifies areas for coordinated management

  • Francisca Samsing
  • Ingrid Johnsen
  • Tim Dempster
  • Frode Oppedal
  • Eric A. Treml
Research Article

Abstract

Context

Sea lice are the most significant parasitic problem affecting wild and farmed salmon. Larval lice released from infected fish in salmon farms and their transport by water masses results in inter-farm networks of lice dispersal. Understanding this parasite connectivity is key to its control and effective management.

Objectives

Quantify the spatial and seasonal patterns in sea lice (Lepeophtheirus salmonis) dispersal in an area with intensive salmon farming. Identify emergent clusters in the network, where associated salmon farms could be used for coordinated management and spatial planning of the industry.

Methods

We used a biophysical model to simulate lice dispersal from 537 salmon farms along the Norwegian coastline for two seasons (spring and winter) from 2009 to 2014. We used network analysis to characterize dispersal pathways and quantify the spatial and temporal patterns in connectivity.

Results

Lice dispersal patterns and network metrics varied greatly between seasons, but differences were consistent amongst years. Winter networks presented more connections, and links were on average two times longer (average winter median = 36.5 ± 7.6 km, mean ± SE; average spring median = 17.8 ± 1.7 km). We identified 12 emergent farm clusters, which were similar across seasons and with the production areas for salmon aquaculture proposed by the Norwegian government.

Conclusions

Seasonal variations in lice development times, oceanographic processes and the topological arrangement of salmon farms affect lice dispersal patterns. We have identified a biologically meaningful and politically tractable alliance structure for sea lice management consisting of closely-associated clusters of farms.

Keywords

Connectivity Spatial epidemiology Cluster analysis Sea lice Lepeophtheirus salmonis Disease management 

Notes

Acknowledgements

Funding was provided by the Research Council of Norway through the Havbruk program to project # 244439 Regional lice assessmenttowards a model based management system to FO & TD, an Australian Research Council Future Fellowship to TD, and an Australian Postgraduate Training Research Scholarship (IPRS) to FS.

Supplementary material

10980_2017_557_MOESM1_ESM.docx (2.8 mb)
Supplementary material 1 (DOCX 2891 kb)

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Copyright information

© Springer Science+Business Media B.V. 2017

Authors and Affiliations

  1. 1.School of BioSciencesUniversity of MelbourneVictoriaAustralia
  2. 2.Institute of Marine Research, NorwayBergenNorway

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