What are the impacts of sea lice from net-pen salmon farms on wild Pacific salmon in British Columbia?

This systematic map will evaluate the existing literature base to assess the effects of sea lice (in the genera Lepeophtheirus or Caligus) from net-pen salmon farms on wild, enhanced or farmed Pacific salmon (Chinook salmon Oncorhynchus tshawytscha, coho salmon O. kisutch, chum salmon O. keta, sockeye salmon O. nerka or pink salmon O. gorbuscha) or Atlantic salmon (Salmo salar) globally. This systematic map will capture evidence available in published and grey literature. We will use a narrative synthesis and descriptive statistics to describe key characteristics of the evidence base (e.g., number of publications, focal salmon and lice species, life stage of salmon and lice, study objectives, exposure and comparator details, outcomes and study designs) and will identify knowledge gaps to inform future research needs and subtopics (evidence clusters) that are sufficiently covered by existing studies to allow full systematic reviewing. Further, the systematic map will provide an indication of whether we can qualitatively or quantitatively assess the effects of sea lice for any identified evidence cluster related to the following sub-questions of interest: (1) To what extent do net-pen salmon farms contribute to the sea lice loads on wild Pacific salmon?, (2) How and to what extent do sea lice affect the performance of juvenile Pacific salmon?, and (3) Does the exposure of sea lice from net-pen salmon farms have a population-level effect on wild Pacific salmon, and if so, to what extent?

This work is being done in collaboration with Fisheries and Oceans Canada (DFO) and will be completed through multiple formal peer-review meetings via the Canadian Science Advisory Secretariat (CSAS) at DFO. The Terms of Reference and objectives of the first two phase of this peer review can be found at:

DFO Terms of Reference for Phase 1, available at: https://csas-scas.dfo-mpo.gc.ca/meetings-reunions/91fa7193-b4c3-42a2-83b8-be726f3a7957?lang=en

DFO Terms of Reference for Phase 2A, available at: https://csas-scas.dfo-mpo.gc.ca/meetings-reunions/fbcdfdc2-793e-4707-b395-caf6068c5e13?lang=en

The above systematic map approach was intended as a first step, with the goal to follow with a systematic review on one or more evidence clusters relating to Pacific salmon identified from the mapping approach. Based on the map findings, studies investigating sea lice effects on individual-level performance metrics (e.g., osmotic function and homeostasis, immune function, and survival) in Pacific salmon were identified as subtopics (i.e., knowledge clusters) that had sufficient coverage for further review. As such, we are using a systematic review approach to estimate how and to what extent sea lice affect the performance of juvenile Pacific salmon. This systematic review will use evidence identified during a systematic map process that included commercially published and grey literature available from 1900 to March 2025. Studies that evaluate the effect of sea lice (in the genera Lepeophtheirus or Caligus) on individual-level performance metrics in the five Pacific salmon species mentioned above found anywhere in the world will be included. Specifically, we will include measures of change related to: (1) a stress response, (2) osmotic function and homeostasis, (3) immune function, (4) injuries, (5) growth, (6) behaviour, (7) survival, (8) reproduction, (9) cardio-respiratory function, or surrogates thereof. Included studies will undergo critical appraisal of internal and external validity. We will build off the coded and extracted information from the mapping exercise by extracting quantitative information on measured outcomes and further exposure and comparator details, as well as effect modifiers (e.g., sea lice infestation level, time since infestation, size and age of salmon). A narrative synthesis will be used to describe the quantity and characteristics of the available evidence, while quantitative syntheses (i.e., meta-analyses) will be conducted to estimate an overall mean and variance of effect for each outcome category separately (e.g., outcome groups 1-9 listed above) when sufficient numbers of similar studies are available. Further, we will attempt to identify sea lice exposure thresholds which could yield valuable information to help inform management for Canadian stakeholders.

Systematic Map: Review Team/Collaborators

Trina Rytwinski – Carleton University, Canada

Steven J. Cooke – Carleton University, Canada

Kathryn Peiman – Carleton University, Canada

Lisa Kelly – Carleton University, Canada

Lily Weber – Fisheries and Oceans Canada

Ian King – Fisheries and Oceans Canada

Sunita Khatkar – Fisheries and Oceans Canada

Amanda Winegardner – Fisheries and Oceans Canada

Shauna Baillie – Fisheries and Oceans Canada

Mark Coulson – Fisheries and Oceans Canada

External Advisory Team

Brian Riddell – Pacific Salmon Foundation

Knut Vollset – NORCE: Norwegian Research Centre

John Reynolds – Simon Fraser University

Kerra Shaw – Fisheries and Oceans Canada

Mark Higgins – Fisheries and Oceans Canada

Systematic Review: Review Team/Collaborators

Trina Rytwinski– Carleton University, Canada