A model of salmon louse production in Norway: effects of increasing salmon production and public management measures

  • Aaen S
  • Helgesen K
  • Bakke M
 et al. 
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Abstract

Salmon lice Lepeophtheirus salmonis Kroyer have caused disease problems in farmed Atlantic salmon Salmo salar L. since the mid-1970s in Norway. High infection intensities and premature return of wild sea trout Salmo trutta L. were first reported in 1992. Later emaciated wild Atlantic salmon smolts carrying large amounts of lice have been observed both in fjords and offshore. The Norwegian Animal Health Authority regulations to control the problem, which came into operation in 1998, included compulsory louse level monitoring in farms and maximum legal numbers of lice per fish. Here, we present a model of salmon louse egg production in Norway and show that the effect of the current public management strategy is critically dependent on the yearly increase in salmon production. This is because the infection pressure is the product of the number of fish in the system, and the number of lice per fish. Due to the much larger number of farmed than wild salmonids, it is highly likely that lice originating from farmed salmon infect wild stock. Estimated tolerance limits for wild salmonids vary widely, and the level of louse egg production in farms which would be needed to decimate wild populations is not known. Two possible thresholds for total lice egg production are investigated: (1) 1986 to 1987 level (i.e. before adverse effects on sea trout were recorded), and (2) a level corresponding to a doubling of the estimated natural infection pressure. The farm lice per fish limits that would have to be observed to keep louse production within the 2 thresholds are calculated for the period 1986 to 2005. A steady decrease in the permitted number of lice per fish may keep the total louse production stable, but the number of salmon required for verification of lice numbers will increase as the prevalence to be verified is decreased. At threshold (2), the model estimated that lice limits should have been 0.05 louse per fish in 1999. This would require 60 fish from each pen to be collected, anaesthetised and examined for a good estimate at a confidence level of 95%. Such sample numbers are likely to be opposed by farmers. The use of national delousing programs to solve the problem is discussed.

Author-supplied keywords

  • *Aquaculture
  • *Biodiversity
  • *Climate Change
  • *Drug Resistance
  • *Ecosystem
  • *Emergencies
  • *Environment
  • *Feeding Behavior
  • *Fisheries
  • *Host-Parasite Interactions
  • *Marine Biology
  • *Oviposition
  • *Phylogeny
  • *Population Dynamics
  • *Predatory Behavior
  • *Salmo salar
  • *Salmon
  • *Seawater
  • Analysis of Variance
  • Animais aqu⡴icos (produ㤡o)
  • Animal Diseases/epidemiology
  • Animal Feed
  • Animal genetic engineering.
  • Animal/*economics/epidemiology
  • Animal/diagnosis/epidemiology/parasitology
  • Animal/pathology
  • Animal/physiology
  • Animals
  • Anthozoa
  • Antiparasitic Agents/*pharmacology
  • Aquacultural biotechnology.
  • Aquaculture
  • Aquaculture/*trends
  • Aquaculture/economics/methods/statistics & numeric
  • Aquaculture/methods
  • Aquatic Organisms
  • Aquatic animals Breeding.
  • Aq赩cultura.
  • Arguloida/*physiology
  • Bacterial Infections/*economics/epidemiology/veter
  • Behavior
  • Bibliographic
  • Biological
  • Blood Chemical Analysis/veterinary
  • Body Size
  • Classical/physiology
  • Classification
  • Cluster Analysis
  • Communicable Diseases
  • Communicable Diseases/epidemiology/microbiology/*t
  • Computer Simulation
  • Conditioning
  • Conservation of Natural Resources
  • Conservation of Natural Resources/*methods
  • Copepoda/*classification/genetics/pathogenicity
  • Copepoda/*drug effects
  • Copepoda/*growth & development
  • Copepoda/*growth & development/parasitology/*physi
  • Copepoda/*physiology
  • Crustacea
  • Crustacea/*physiology
  • Databases
  • Eating/*physiology
  • Ecology
  • Ecosystem
  • Ectoparasitic Infestations/*complications/epidemio
  • Ectoparasitic Infestations/*veterinary
  • Ectoparasitic Infestations/blood/parasitology/phys
  • Ectoparasitic Infestations/diagnosis/epidemiology/
  • Ectoparasitic Infestations/drug therapy/parasitolo
  • Ectoparasitic Infestations/economics/prevention &
  • Ectoparasitic Infestations/epidemiology/*veterinar
  • Ectoparasitic Infestations/epidemiology/parasitolo
  • Ectoparasitic Infestations/parasitology/*veterinar
  • Ectoparasitic Infestations/parasitology/physiopath
  • Ectoparasitic Infestations/parasitology/prevention
  • Electronic books.
  • Emerging/epidemiology/microbiology/transmission/vi
  • Engenharia gen⥴ica.
  • Environment
  • Environmental Monitoring/*methods
  • Feeding Behavior/*physiology
  • Female
  • Fish Diseases/*diagnosis/epidemiology/parasitology
  • Fish Diseases/*economics/*parasitology/prevention
  • Fish Diseases/*economics/epidemiology
  • Fish Diseases/*parasitology
  • Fish Diseases/*parasitology/physiopathology
  • Fish Diseases/blood/parasitology/*physiopathology
  • Fish Diseases/drug therapy/*parasitology/preventio
  • Fish Diseases/epidemiology
  • Fish Diseases/epidemiology/*parasitology/transmiss
  • Fish Diseases/parasitology/*prevention & control
  • Fisheries
  • Fisheries/*economics/methods/statistics & numerica
  • Fisheries/*methods
  • Fisheries/economics/statistics & numerical data
  • Fishes
  • Fishes/*growth & development
  • Food
  • Food Chain
  • Food Supply
  • Food Technology
  • Fresh Water/*analysis
  • Genotype
  • Gills/parasitology
  • Hantavirus/physiology
  • Hematocrit/veterinary
  • Host-Parasite Interactions
  • Host-Pathogen Interactions
  • Humans
  • Hydrocortisone/*metabolism
  • Insecticides/pharmacology
  • Larva/*growth & development
  • Larva/growth & development
  • Larva/physiology
  • Least-Squares Analysis
  • Legislation
  • Lice Infestations/*parasitology
  • Life Cycle Stages
  • Life Cycle Stages/physiology
  • Light
  • Linear Models
  • Lyme Disease/microbiology/transmission
  • Male
  • Marine Biology/*methods
  • Models
  • Mollusca/*microbiology
  • Monte Carlo Method
  • Motivation/physiology
  • Newborn/physiology
  • Norway
  • Oceans and Seas
  • Oxygen Consumption/*physiology
  • Oxygen/metabolism
  • Parasitic Diseases
  • Pest Control/*economics
  • Pest Control/trends
  • Pesticides/*pharmacology
  • Pesticides/adverse effects
  • Phytoplankton/growth & development
  • Population Density
  • Population Dynamics
  • Predatory Behavior
  • Prevalence
  • Random Allocation
  • Risk Factors
  • Salinity
  • Salmo salar/*parasitology
  • Salmo salar/*physiology
  • Salmon/*parasitology
  • Salmon/*physiology
  • Salmonidae/*parasitology
  • Scotland
  • Seafood/economics/microbiology/parasitology/virolo
  • Seasons
  • Seawater/*chemistry
  • Seawater/chemistry
  • Skin/parasitology/pathology
  • Sodium Chloride
  • Species Specificity
  • Survival Analysis
  • Survival Rate/trends
  • Temperature
  • Time Factors
  • Toxicity Tests
  • Vaccination/veterinary
  • Virus Diseases/*economics/epidemiology/veterinary
  • Wild
  • Wild/parasitology
  • Zoonoses/epidemiology/transmission

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Authors

  • S M Aaen

  • K O Helgesen

  • M J Bakke

  • K Kaur

  • T E Horsberg

  • J L Blanchard

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