Monitoring sea-louse parasites on juvenile wild salmon in Clayoquot Sound on the West Coast of Vancouver Island, British Columbia, Canada
This repository contains data from long-term monitoring of juvenile salmon for sea lice, by the Cedar Coast Field Station. To view our research, visit Archives.
Last update: 11/26/2021
- Before using the data, please read the associated metadata (below)!
This project aims to examine the dynamics between wild juvenile Pacific salmon and sea lice infestation levels in the declining population of wild salmon located in Clayoquot Sound, British Columbia on the West Coast of Vancouver Island. During the 2018, 2019, 2020, and 2021 salmon out-migrations, we conducted beach seine surveys and sea lice monitoring in the near-shore environment of Clayoquot Sound. There is a well-established correlation between sea lice abundance on salmon farms and abundance on wild juvenile salmon. By expanding our dataset and solidifying site and sampling consistency, we hope to improve our understanding of the influences of sea lice on juvenile salmon and inform local management strategies.
Keywords: aquaculture, conservation, parasite, Pacific salmon, sea lice, host-parasite dynamics
Sea lice (Lepeoptheirus salmonis & Caligus clemensi) are naturally occurring crustacean ectoparasites of wild salmon (Beamish et al, 2009; Skern-Mauritzen et al., 2014). The salmon louse (l. Salmonis) is a salmon specific parasite, meaning it can only survive and reproduce on salmon and trout (Costello, 2006). C. Clemensi is a generalist ectoparasite that can survive and reproduce on many fish species. Sea lice transmission is influenced by many factors, notably: temperature, salinity, and host presence and abundance (Costello, 2006; K. M. Brooks, 2009; Stien et al., 2005). Increased temperature and increased variability in temperature may increase sea lice abundance and reduce sea lice generation time. In high numbers, sea lice can negatively affect salmon survival, especially in juvenile fish (Costello, 2009).
In a natural environment, juvenile salmon are rarely parasitized by sea lice because of the gaps in seasonal migrations of juvenile and adult salmon, which reduces interaction between the generations (Costello, 2009). Adult Pacific salmon generally return to spawn in late Summer and Fall. Juvenile salmon leave the freshwater and enter the near-shore marine environment in the early Spring and out-migrate to the ocean. Because of this natural mismatch, juvenile salmon do not interact with high abundances of adult salmon until they have left the nearshore environment, limiting exposure to marine parasites and infectious agents (Costello, 2009). In areas without salmon farming, like the North Coast of BC, a natural abundance of sea lice between 0.05 and 0.1 lice per juvenile pink salmon was reported (Gottesfeld et al., 2009).
Salmon farms increase the transmission of sea lice to juvenile wild salmon as they migrate past salmon farms (Krkošek et al., 2005). Salmon farms operate year-round, with some farms holding up to 500,000 salmon. The year-round operation of salmon farms breaks the natural time buffer that prevents pathogen and parasite transmission between adult and juvenile Pacific salmon. Adult Pacific salmon and Pacific Herring entering the nearshore environment from the ocean can transmit sea lice and other diseases to Atlantic salmon on farms (Costello, 2006). Then, farms can sequester and enhance the transmission of sea lice and other pathogens that can then spillback to juvenile salmon and herring when they migrate past the farms. Juvenile wild salmon are exposed to unnatural levels of sea lice infestation when they pass near salmon farms (Krkošek et al., 2005). A sea lice abundance of approximately 0.5 lice per fish was reported in 2015 on wild juvenile salmon in the Broughton Archipelago (Bateman et al., 2016). This lice abundance was predicted to correspond to an approximately 23% (9-39%) lice-induce mortality of juvenile salmonids that year. In Clayoquot Sound, 20 open-net-pen salmon farm tenures are in the migratory routes of wild Pacific salmon with upwards of 12 operating at any given time.
Fig. 1 Illustration of fish farm wild salmon and sea lice dynamic. Adult wild salmon bring sea lice to coastal waters where they can proliferate on farm and then spill back to juvenile salmon when they migrate past farms in the spring. Sea lice die in fresh water with their adult salmon hosts and so sea lice are not passed from adult to fry when fry first emerge and migrate to sea.
Open net-pen salmon farms are a major threat to wild juvenile salmon populations as they travel along their migration routes (Dill et al., 2011). Several studies have addressed the negative impacts of salmon farms on both individual juvenile salmon and their populations (Bateman et al., 2015; Connors et al., 2010; Godwin et al., 2017; Krkose et al., 2005; Krkosek et al., 2007; Morton & Routledge, 2005; Peacock et al., 2013). When Juvenile salmon enter the nearshore environment they have not yet developed competent immune and osmoregulatory systems, including a lack of scales and body mass necessary to resist sea lice infestations (Sackville et al., 2011). L. salmonis have shown to be pathogenic, causing disease, to juvenile Atlantic, sockeye, and pink salmon (Costello, 2009; Long et al., 2018). Louse induced mortality has been observed on juvenile Atlantic salmon with infection levels of three chalimus (attached) stage lice per gram of host weight and no external lesions (Wagner et al., 2008). Notably, pathogenicity and mortality levels are derived at the individual level from clinical experimentation and do not directly correlate to lice-induced mortality levels in wild juvenile salmon populations (Bateman et al. 2016; Krkosek et al., 2011; Peacock et al., 2013). However, studies have shown that sea lice abundance in conjunction with predation pressures, food availability, and other factors can influence lice-induced mortality and the population-level impacts of sea lice infestation (Krkosek et al., 2011; Peacock et al., 2013). Juvenile salmon that enter the marine environment as smolts may not succumb to louse infestations outright but are likely to experience sub-lethal impacts like a reduced foraging ability, ultimately reducing their likelihood of surviving to adulthood (Godwin et al., 2017).
Since 2018, CCFS has carried out monitoring of sea-louse infestation levels on wild-caught juvenile salmon in Clayoquot Sound, BC, an area of active salmon aquaculture. The data collected through this monitoring program will be used to describe trends and patterns in host parasite dynamics between wild Pacific salmon and sea lice in Clayoquot Sound, BC. This continued monitroing will help answer questions with ecological, conservation, management and policy relevance.The data for the CCFS sea lice monitroting program is publicaly avalible here.
- Clayoquot_Fish_VariableDescriptions- describes columns ClayoquotSeaLice_Fish_Data.csv
- Clayoquot_Site_VariableDescriptions- describes columns in ClayoquotSeaLice_Site_Data.csv
- Figures - subfolder containing all figures.
- ClayoquotSeaLice_Fish_Data.csv- contains the individual fish health and sea louse counts for the 2018, 2019, and 2020 seasons
- ClayoquotSeaLice_Site_Data.csv- contains descriptions and characteristics of the sampling sites for sea lice monitoring on juvenile wild salmon
Sitka Foundation, 625 Howe St, Vancouver, BC V6C 2T6, Canada
Cedar Coast Field Station Society, P.O.Box 1209 Tofino, BC V0R 2Z0
In-kind contributions of volunteers, equipment, and boat time from Uu-a-thluk Fisheries, Ahousaht Fisheries, Ahousaht Guardians, Salmon Coast Field Station, Fisheries and Oceans Canada and the Hakai Institute.
We acknowledge that we operate within the traditional and unceded territories of the Ahousaht and Tla-o-qui-aht Nations. Completing this sampling was a huge team effort and we really appreciate the support from the Cedar Coast crew: Julia Simmerling, Mack Bartlett, Satchel Robertson, Simon Nessman, Claudia Tersigni, Rowen Monks, Christian Carson, and Kayley Hollyer . We had great external support and would like to thank the crews at Uu-a-thluk Fisheries, Ahousaht Fisheries, Ahousaht Guardians, Salmon Coast Field Station, Fisheries and Oceans Canada and the Hakai Institute. Technical support from Jared Dick, Sean Godwin, Andrew Bateman, Martin Krkosek, and Alexandra Morton. This work would not be possible without the support of Ocean Outfitters,and the Sitka Foundation.
