Canadian Aquaculture R&D Review 2007

Sea Lice

Sea Lice on the Move

The circulation of waters in the Broughton region of BC has been the subject of a recently completed ACRDP project and a component of a new ACRDP project to investigate the life history of sea lice. Field programs and numerical circulation models have significantly increased the knowledge and understanding of the circulation of this complex region and identified key areas for further research. Scientists have used particle tracking software and numerical model currents to simulate the movement of pathogens, toxic algal blooms and planktonic larval stages of salmon louse from different source locations. These particle tracking simulations provide estimates of the transport pathways, distances traveled and concentration of particles in the model region.

In this project the researchers plan to conduct detailed measurements of near surface circulation at several farm sites and other areas of interest using GPS tracked surface drifters.

The drifter experiments will also be used to verify model representations of the mean surface circulation and to compare with our particle tracking simulations. Furthermore, the researchers plan to extend the program of current meter observations in order to have observations of current movements that are coincident with the drifter experiments.

Research team: Dario Stucchi, Mike Foreman and Clare Backman. For information contact Dario Stucchi (Email: StucchiD@pac.dfo-mpo.gc.ca). Submitted by DFO (ACRDP) and Marine Harvest Canada

Estimating the risk

The objectives of this project are to assess the effect of sea lice infestation levels on the swimming and reproductive ability of salmonid species native to British Columbia. It will also identify the effect and source of sea lice on wild migrating fish stocks, and construct a risk assessment model to help predict the risk of infestation from sea lice in areas with and without farming activity.

Using innovative telemetry technology, the project tracked migratory paths of salmon to determine the risk of infestation during their outmigration. The project has determined the effects of various infestation levels on fish physiology and verified stable isotope ratios as a reliable tool to trace the origin and migration routes of sea lice found on wild and farmed salmon. The data can be used to calculate the number and location of farms to site in a specific area to minimize the risk of transmission of sea lice to the passing wild salmon. A risk assessment model for Atlantic salmon is in progress and will be published.

The provincial government of British Columbia provided funding for an international conference on sea lice biology and control that identified research priorities and led to new collaborative research projects. The project results will have considerable effect on public policy and help guide coastal management and have created a high level of interest at the provincial and federal government levels.

Research Team: R. Scott McKinley, Bengt Finstad, John Burka. For information contact Scott McKinley (Email: mckin@interchange.ubc.ca). Submitted by AquaNet.

May ’03-Mar. ’05

Research could lead to sea lice vaccine

Sea lice are parasitic copepods that live on the external surfaces of their hosts. One species, the salmon louse, Lepeophtheirus salmonis is an economically important parasite of both wild and farmed salmonids. On most host species there is limited host tissue response to attachment and feeding of this

species. This observation has led to the view that L. salmonis, like other arthropod parasites (e.g. ticks), secretes compounds that modulate host immune responses and ensure their survival on hosts.

We have partially identified and characterized secretory compounds of L. salmonis. Similar to ticks, L. salmonis produces a complex mixture of both protein and non-protein components such as prostaglandin E2 (PGE2), which is well documented to have major effects on immune function in other vertebrates. These compounds have been shown to reduce the expression of Atlantic salmon genes involved in inflammation using Real-Time PCR. Inflammation has been identified as being a very important mechanism with respect to the rapid loss of L. salmonis from coho salmon, a species on which L. salmonis fails to survive.

This study provides the first hard evidence for immunomodulation by a parasitic copepod. These data are not only an important foundation for future studies of parasitic copepod host-parasite interactions but have led to the formulation and testing of a sea lice vaccine in collaboration with Microtek International. We are proceeding with further vaccine trials within the laboratory prior to testing in a cage culture system.

Research team: Mark Fast, Stewart Johnson, Neil Ross. For information contact Mark Fast (Email: mark.fast@nrc-cnrc.gc.ca). Submitted by Institute for Marine Biosciences, NRC, Halifax, Nova Scotia.

Sept.’04-Mar.’07.

Incorporating natural cycles of sea lice production into management for sustainable aquaculture

The Broughton region is an important area for wild salmon and for salmon farming. Concern over pink salmon in the Broughton region was raised when the escapement in 2002 declined following a record high escapement in 2000. This decline in escapement was associated with sea lice on the juvenile salmon. It was suggested that an increase in sea lice occurred as a result of salmon farming. Our studies examined the wild production of pink salmon. The Glendale spawning channel facility was built in 1989 and has had a major influence on pink salmon production. In recent years, the escapement of adult pink salmon to the Glendale represents over 70% of all escapement to this region. The marine survival of pink salmon to the Broughton region from year to year is variable. There was good survival in 2003/2004, average survival in 2004/05 and lower survival in 2005/06.

The decrease in survival and resulting escapement in 2005/06 is not restricted to this region but is being observed throughout British Columbia. Our study also documented the abundance of sea lice on adult salmon and on fish farms in the study region to improve our understanding of the dynamics of sea lice. Virtually 100% of the adult Pacific salmon returning to the coastal waters were highly infected with sea lice. We suggest that this transport of sea lice from the high seas to the coastal waters is an important part of the sea lice life history strategy. A study examining the production of sea lice on a fish farm located at the junction of Knight Inlet and Tribune Channel is currently being completed. This work will improve our understanding of the dynamics and timing of sea lice production in the coastal region.

Research team: Richard Beamish, (DFO, PBS), Chrys Neville, Ruston Sweeting, Grace Karreman, Sonja Saksida. For information contact Richard Beamish (Email: Beamishr@pac.dfo-mpo.gc.ca). Submitted by DFO(ACRDP).

May ’05-Jun ’07

Are wild Pacific salmon susceptible to sea lice infection?

Researchers test the hypotheses

There is a concern that farmed Atlantic salmon affects the health of wild Pacific salmon by acting as reservoirs for the salmon louse, Lepeophtheirus salmonis. However, the susceptibility of juvenile Pacific salmon to the parasite is poorly understood. Researchers tested the hypotheses that juvenile pink and chum salmon are equally susceptible to L. salmonis and, that a nutrient-deficient diet is associated with more severe L. salmonis infestations.

They found that the prevalence and abundance of L. salmonis following laboratory exposures to 243 or 735 copepodids per fish was significantly higher on chum compared to pink salmon. The weight and hematocrit of exposed chum salmon was significantly less than unexposed chum salmon. Neither weight nor hematocrit of pink salmon was affected by sea louse exposure. No mortality was observed among either species of salmon and most lice were lost by 28 days.

Species differences in cortisol response, expression of proinflammatory genes and histological inflammatory lesions, were linked temporally to parasite elimination. In addition, a reduced diet significantly affected the expression of immune genes in the juvenile salmon but parasite abundance was not affected. There is a relatively enhanced innate resistance to L. salmonis in healthy, juvenile pink salmon.

Research team: Simon Jones, Stewart Johnson, Mark Fast, David Groman. For information contact Simon Jones (Email: joness@pac.dfo-mpo.gc.ca). Submitted by DFO (ACDRP).

Mar. ’06-Mar. ’07

Testing sea lice loads

The objective of the study was to quantify the relative susceptibility of species of juvenile salmon to infection by salmon lice in laboratory and marine environments.

In 2003, laboratory tanks containing juvenile pink, chum and chinook salmon were artificially infected with a standardized level of infective salmon lice (low exposure level). A second tank of chinooks (high exposure level) was infected with twice the standardized level of lice. The number of salmon lice/fish and mortalities were recorded daily for 30 days following infection. The following year (2004) laboratory tanks containing juvenile pink and chum salmon were again artificially infected with lice at the ‘high’ and ‘low’ exposure levels.

The juvenile chums (2003 batch) had significantly lower levels of lice/fish than pinks or Chinooks and levels of lice/fish on pinks and chinooks did not differ significantly. The ‘high exposure’ group of chinooks had significantly higher lice levels than any of the ‘low exposure’ groups. Each group of infected fish had a mortality rate higher than groups of uninfected fish. In addition, the ‘high exposure’ chinooks had a 41% higher mortality rate than ‘low exposure’ chinooks.

The ‘low exposure’ chum salmon had an average of 44 lice/fish while the ‘high exposure’ chum infection level was 87 lice/fish. In contrast, the average infection level for the ‘low exposure’ pink salmon was 0.05 lice/fish – while the ‘high exposure’ pink infection level was 1.52 lice/fish. These results indicate that: (i) pink and chum salmon differ in their ability to resist infection by salmon lice; (ii) higher lice levels in the marine environment may lead to higher levels of infection.

Research team: A. Mazumder.. For information contact Asit Mazumder (Email: mazumder@uvic.ca). Submitted AquaNet.

Government's Role - Challenge

Can carotenoid pigments help determine the origin of sea lice?

The objective of this study was to assess the potential of carotenoid pigments for determining the origin of salmon lice infecting pink salmon smolts in the Broughton Archipelago. To do this carotenoid pigments were extracted from salmon lice from wild and farmed salmon in the Broughton Archipelago – as well as tissue samples from both wild and farmed salmon.

The study showed that the carotenoid pigment composition of salmon feeding on wild prey differed from that of salmon consuming food containing synthetic pigments. This confirms that pigment composition could be used to differentiate wild and farmed salmon.

However, salmon lice collected from wild and farmed salmon could not be differentiated on the basis of their carotenoid pigment composition. This finding suggests that the origin of salmon lice infecting wild juvenile salmon in the Broughton Archipelago may not be determined unequivocally via the characterization of carotenoid pigments.

While characterization of pigment composition was ineffective in differentiating salmon lice from farmed and wild salmon, chemical tracers may still provide a useful approach in determining the source of the lice infecting juvenile salmon. Since large differences in fatty acid and stable isotope profiles have been observed in wild and cultured salmon, characterization of these profiles in lice may prove valuable in identifying the source of salmon lice infestations.

Research team: Marc Trudel, J.N.C. (Ian) Whyte, Simon Jones, Keng Pee Ang. For information contact Mark Trudel (E-mail: trudelm@pac.dfo-mpo.gc.ca). Submitted by BCARDC.

Researching resistance

This research is aimed at developing strategies to identify and monitor sea lice sensitivity to emamectin benzoate (SLICE®). Due to the limited chemotherapeutic options available, there is a continued reliance on emamectin benzoate for the control of sea lice on farmed Atlantic salmon, making resistance development a major concern. Two major mechanisms of avermectin resistance in arthropods and nematodes, P-glycoproteins (P-GP) and avermectin receptors (glutamate- and GABA-gated chloride channels) have been identified in sea lice.

We have examined the expression of P-GP in sea lice and its potential role in resistance development using poly and monoclonal antibodies in western blots and immunohistochemistry and have identified P-GP in sea lice intestinal epidermis.

This is the first evidence of a multidrug efflux pump in sea lice which will allow detection of upregulation, should resistance to emamectin benzoate develop. P-GP expression in sea lice is being examined using realtime RT-PCR which will be an excellent tool for measurement of P-GP upregulation. We have also identified the genes for the avermectin target sites, glu- and GABA-gated chloride channels.

Experiments are now underway to express glu- and GABA-receptors from the genes identified and

compare the binding characteristics to those in situ. The development of both molecular and biochemical tools will aid in the early detection of resistance allowing veterinarians and fish farm personnel to make decisions on alternative treatment measures.

Research team: John Burka and Larry Hammell. For information contact John Burka (Email: burka@upei.ca). Submitted by AquaNet.

Apr. ’02-Dec. ’06.

Salmon/sea lice interactions

This study is about how salmon aquaculture changes the ecology of a native host parasite system (sea lice and salmon) and how this challenges the conservation of wild Pacific salmon. The research is highly collaborative and involves a combination of fieldwork, experimentation, and modeling. The first step has been understanding how aquaculture changes the natural transmission dynamics of the parasite. Because salmon are migratory, juvenile and adult salmon are spatially separated and this means that juvenile salmon experience a natural refuge from parasites in early marine life. Salmon farms may undermine this refuge by providing a reservoir for lice that exposes juvenile salmon in early marine life. This effect may have dramatic consequences on salmon survival - sea lice are widely considered benign on adult salmon, but when infecting juvenile salmon they are a severe pathogen. Only one or two lice are lethal and this may correspond to a 9-95% mortality in juvenile salmon populations due to parasite transmission from farm salmon. It still remains unknown if these dynamics place new limits on wild salmon populations as a whole. Circumstantial evidence suggests that affected wild salmon populations have declined, however, a thorough analysis has yet to be undertaken.

Research team: Martin Krkosek. Submitted by NSERC.

Susceptibility compared

This project will build on ongoing research and seek answers to questions that are relevant to understanding the impacts of L. salmonis infections on juvenile pink and chum salmon. It will pose the following questions: how does the susceptibility compare with that of juvenile Atlantic salmon, what is the effect of prior exposure to L. salmonis on the establishment and outcome of subsequent infections, and are differences in susceptibility between species related to differences in how L. salmonis responds to the different host species?

Research team: Simon Jones, Stewart Johnson, Mark Fast, David Groman, Keng Pee Ang, Betram Svanvik. For information contact Simon Jones (Email: joness@pac.dfo-mpo.gc.ca). Submitted by the Pacific Salmon Forum.

Mar. ’06-Mar. ’07

Monitoring sea lice in Clayoquot Sound

This study will measure prevalence and intensity of sea lice over time and space in the Bedwell Sound and Tofino Inlet emigration routes in Clayoquot Sound. It will record data on growth patterns of sampled salmonids; record abundances of salmonids; and work with DFO and others to provide integrated understanding of results and to further develop cooperative sea lice monitoring programs between First Nations and industry.

Research team: Mike Jacobs, Don Hall, Darrell Campbell, Andrew Jackson, Spencer Evans, Randy Mercer. For information contact Mike Jacobs (Email: mjacobs@nuuchahnulth.org). Submitted by the Pacific Salmon Forum.

Mar.-Dec.’06

Sea lice potpourri

This project is intended to answer a number of questions: is there significant infection of sea lice on juvenile pink salmon in between Sargeaunt Pass and Glendale Creek (areas where there are no fish farms)? How and when and where do juvenile pink salmon from Glendale Creek first acquire sea lice? When and how does a fish farm become infected with sea lice and is there amplification of sea lice? Given that sticklebacks commonly occur in and around net pens, what role do they play, if any, in the connectivity of lice on farmed and wild salmon? What happens to sea lice on wild fish after SLICE treatments? And is there an over-winter stage of L. salmonis or C. cleminsi that is missing from our current understandings of the life cycle?

Research team: R.J. Beamish, Chrys Neville, Ruston Sweeting, Simon Jones, R. Kabata, Bill Pennell, Grace Karreman, Dale Blackburn. For information contact Richard Beamish (beamishr@pac.dfo-mpo.gc.ca). Submitted by the Pacific Salmon Forum.

Apr. ’06-Mar. ’07

North Coast sea lice research

This project was designed to examine the hypothesis that sea lice, especially L. salmonis are transmitted by returning adult salmon to migrant salmon juveniles about to enter the inshore coastal waters. It’s intended to test whether L. salmonis levels increase as vectors become abundant in the juvenile migrant staging areas of coastal waters in northern BC.

Research team: Allen Gottesfeld, Bart Proctor, Dave Rolston, R.J. Beamish, Dave Peacock. For information contact Allen Gottesfeld (Email: Gottesfeld@skeenafisheries.ca). Submitted by the Pacific Salmon Forum.

Apr. ’05-Apr. ’07

Tallying pinks in the Broughton

This project estimates the abundance of juvenile pink and chum salmon in the Broughton in July 2006 in order to determine if the area around the salmon farms is a passageway for migrating juvenile salmon or a rearing area as well as a migration corridor. It will also determine the health of the juvenile salmon that reared in the Broughton area in July 2006.

Research team: R.J. Beamish, Chrys Neville, Ruston Sweeting, Grace Karreman. For information contact Richard Beamish (Email: beamishr@pac.dfo-mpo.gc.ca). Submitted by the Pacific Salmon Forum.

Jul.-Nov. ’06

Do sticklebacks play a role?

This project will produce a literature review of the biology and ecology of the stickleback; provide preliminary data on their habitat use, on-host choice and host-switching behavior of L. salmonis.

Research team: Lawrence Dill. For information contact Lawrence M. Dill (Email: ldill@sfu.ca). Submitted by the Pacific Salmon Forum.

Mar. ’06-Mar. ’07

Managing sea lice: does it work?

This proposal has three components: farm sea lice sampling, spatial sampling of juvenile pink and chum salmon for sea lice before and after they pass the treated farms and data analysis and modeling to detect and estimate transmission from farm salmon to wild salmon.

Research team: John Volpe, Martin Krkosek, Mark Lewis, Craig Orr. For information contact John Volpe (Email: jpv@uvic.ca). Submitted by the Pacific Salmon Forum.

Mar.-Jul.’06

Pilot study to evaluate sea lice sampling procedures

This project is expected to result in identification of particular locations in the survey region where sea lice larvae congregate in appreciable concentrations or are repeatedly found. It will also provide improved understanding of the vertical distribution of sea lice larvae; insight into preferred habitats or locations of planktonic sea lice larvae; identification of environmental factors associated with sea lice larvae and assessment of temporal distributions. Also being investigated is generic market analysis and evaluation of light traps as effective remote sampling devices for capturing planktonic sea lice larvae.

Research team: Dario Stucchi, Moira Gallbraith, Martin Krkosek, I. Novales Flamarique, R. Mercer. For information contact Dario Stucchi (Email: stucchid@pac.dfo-mpo.gc.ca). Submitted by the Pacific Salmon Forum.

Apr. ’06-Mar. ’07

Researchers study impact of sea lice on coho and chinook salmon

These laboratory based studies will provide data on the effects of sea lice infestation on the health of coho and chinook, the most severely declining of all Pacific salmon species. To date, it is not known just how many sea lice are detrimental to the health of migrating juvenile Pacific salmon. These data in conjunction with the results of the BCARDC project will provide a benchmark that can be used to decipher the data collected by DFO sea lice surveys that record infection intensity. This will enable the ascertainment of the risks posed by sea lice to wild juvenile salmon. Field studies will show the impacts of sea lice on specific wild salmon stocks deemed to be at risk by stakeholders in the Broughton.

Research team: Kevin Butterworth, Scott McKinley, Fiona Cubitt, Bengt Finstad, Diane Morrison, Tony Farrell. For information contact Kevin Butterworth (Email: kevingb@interchange.ubc.ca ). Submitted by the Pacific Salmon Forum.

Apr. ’05-Mar. ’07

Does sea lice infestation increase predation risk?

SFU graduate student Paul Mages was awarded the Pacific Salmon Forum’s first directed research grant for student research into wild/farmed fish interactions with a focus on disease and/or parasite transfer. His study is entitled, Early Marine Survival of Pink Salmon: Effects of Sea Lice on Predation Risk. One of the unanswered questions about the impact of sea lice on pink salmon is whether sea lice infestations increase the chances of very young pinks being killed by predators (most commonly, juvenile coho salmon). Mages is going to test whether young pinks, once they are infested, are more prone to be killed by juvenile coho, either because the infestation affects their swimming speed or because it causes them to take greater risks getting food, which in turn makes them more vulnerable to predators.

Research team: Paul Mages. For information contact Paul Mages (Email: pmages@sfu.ca). Submitted by the Pacific Salmon Forum.

Evaluating the enumerators

This study will evaluate the use of DIDSON sonar on the Glendale main-stem to enumerate returning pink salmon and to provide an in-season calibration to the over-flight observations of pink salmon to that system.

Research team: Pieter Van Will, Dr. John Holmes, Dean Wyatt. For information contact Pieter Van will (Email: vanwillp@pac.dfo-mpo.gc.ca). Submitted by the Pacific Salmon Forum.

May ’06-Feb. ’07

Sea lice monitoring continued

Objectives of this study are to continue (and to harmonize) the annual monitoring of sea lice infection of juvenile pink and chum salmon in the Broughton and Knight Inlet; and to conduct more intensive sampling of juvenile pink and chum salmon in Tribune Channel and Knight Inlet to obtain additional information on the patterns of sea lice infection of wild salmon in these areas in 2006 and 2007

Research team: Brent Hargreaves, Simon Jones, Alexandra Morton. For information contact Brent Hargreaves (Email: hargreavesb@pac.dfo-mpo.gc.ca). Submitted by the Pacific Salmon Forum.

Mar. ’06-Nov. ’06