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Defining the risk of sea lice infections through the development of an understanding of the early life history population dynamics of sea lice associated with Atlantic salmon aquaculture sites in the Bay of Fundy

PARR-2014-M-02

Description

A better understanding of how the early life stages of sea lice infect fish on salmon farms is essential to implementing more effective management measures aimed at disrupting the reproductive cycle of sea lice. Data supporting past management approaches have treated sea lice larval stages as passive particles thought to be swept away from farms with oceanographic currents is scarce. Field sampling has shown that planktonic sea lice larvae are most often found in close proximity to active salmon farms, and lab studies have shown that sea lice populations can successfully reproduce in tanks with high flushing rates. These observations suggested that larval stages are far from being passive particles, and that they have certain characteristics at this life stage that allow them to remain on salmon farms rather than being passively flushed away by currents. The rapid proliferation of sea lice to epidemic levels results in significant challenges to the aquaculture industry, and can have unintended impacts on wild populations, including other fish and invertebrates. This project examined the relative risk of amplification and transmission of sea lice within the salmon aquaculture industry in the Bay of Fundy. The research provides insight into infection dynamics within a farm as well as an assessment of the risk of transmission of sea lice to wild salmon.

Figure 1. Photograph of sea lice larvae (nauplius)

Findings

Larval sea lice were sampled in the waters near and far from salmon aquaculture sites. Sea lice larval densities were significantly higher at farm sites than reference sites. The farm site densities dropped an order of magnitude (i.e.,10-1) at a distance of 100 m from the cages. The majority of the larvae captured in the study were in the first larval stage, known as nauplii (93%). The remaining 7% were in the infective copepodite larval stage, any of the five stages before sexual maturity. Sea lice densities ranged from 0 to 10 larvae per m3. The results of this study suggest that the early life history stages of sea lice originate from and may remain close to active salmon farms.

Publications

Nelson, E. J., Robinson, S. M. C., Feindel, N., Sterling, A., Byrne, A. and Pee Ang, K. 2018. Horizontal and vertical distribution of sea lice larvae (Lepeophtheirus salmonis) in and around salmon farms in the Bay of Fundy, Canada. Journal of Fish Diseases 41(6): 885-899.

Multimedia

Aquaculture research: Alternative control methods for managing sea lice

Program Name

Program for Aquaculture Regulatory Research (PARR)

Year(s)

2014 - 2017

Principal Investigator(s)

Shawn Robinson
Research Scientist, Fisheries and Oceans Canada, St. Andrews Biological Station, Maritimes Region
Email: Shawn.Robinson@dfo-mpo.gc.ca

Team Member(s)

Terralynn Lander, Biologist, Fisheries and Oceans Canada, St. Andrews Biological Station, Maritimes Region

Emily Nelson, Biologist, Fisheries and Oceans Canada, St. Andrews Biological Station, Maritimes Region

Fred Page, Research Scientist, Fisheries and Oceans Canada, St. Andrews Biological Station, Maritimes Region

Collaborator(s)

Keng Pee Ang, Cooke Aquaculture Inc.

Gregor Reid, University of New Brunswick

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