AEI 7:267-280 (2015)  -  DOI: https://doi.org/10.3354/aei00155

FEATURE ARTICLE
Statistical and ecological challenges of monitoring parasitic salmon lice infestations in wild salmonid fish stocks

Ingeborg Palm Helland1,*, Ingebrigt Uglem1, Peder A. Jansen2, Ola H. Diserud1, Pål Arne Bjørn3, Bengt Finstad

1Norwegian Institute for Nature Research, PO Box 5685 Sluppen, 7485 Trondheim, Norway
2Norwegian Veterinary Institute, PO Box 750 Sentrum, 0106 Oslo, Norway
3Institute of Marine Research, PO Box 6404, 9294 Tromsø, Norway
*Corresponding author:

ABSTRACT: Ecological monitoring programmes should provide precise data to inform management, but the data quality is often limited by methodological challenges and the need for cost-effective sampling. Parasite infestations are particularly challenging to monitor due to complex interactions among hosts, parasites and the environment. In Norway, salmon lice infestations on wild salmonid fish have been monitored since 1992 to survey the potential transmission between farmed and wild salmonids. Here, we compared spatiotemporal variation in salmon lice levels with variations in local fjord conditions, including salinity, temperature and infestation pressure from salmon farms (measured as mean abundance of mature female lice × number of farmed fish). We tested 3 different measures of infestation with different statistical properties. Our results confirm that, even after correcting for temperature and salinity effects, infestation pressure from salmon farms significantly increases the probability of lice infestation in wild salmonids. The probability of infestation increases with fish body length, salmon farm infestation pressure and temperature, and decreases with increasing freshwater influence. Furthermore, we found a significant interaction between temperature and infestation pressure from salmon farms. When the infestation pressure from farms is low, temperature has a strong increasing effect on the probability of infestation, but as the infestation pressure from farms increases, temperature gradually becomes less important. The exact results vary somewhat depending on the measure of lice infestations used, but the same trend can be seen in all models. We discuss the statistical and biological complexities that make monitoring of salmon lice in wild populations challenging.


KEY WORDS: Lepeophtheirus salmonis · Zero- inflation · Salmon farming · Temperature · Salinity · Salmo spp. · Caligus elongatus · Norway


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Cite this article as: Helland IP, Uglem I, Jansen PA, Diserud OH, Bjørn PA, Finstad B (2015) Statistical and ecological challenges of monitoring parasitic salmon lice infestations in wild salmonid fish stocks. Aquacult Environ Interact 7:267-280. https://doi.org/10.3354/aei00155

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