Scientific research on sea lice

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Alternative control methods for managing sea lice

Alternative Control Methods for Managing Sea Lice Video

Science is the key to an environmentally sustainable aquaculture industry. Fisheries and Oceans Canada (DFO) scientists and researchers work diligently to build understanding and knowledge about sea lice, their relationship to the marine environment and fish, and the treatments and methods used to reduce their abundance near wild and farmed species. Some research activities are conducted within the Department, while other activities are collaborations with scientists and researchers from universities in Canada, other levels of government, industry, and international partners.

Innovation

Scientists and researchers are looking at innovative methods to control sea lice that are both effective and environmentally responsible:

Researchers are exploring the use of physical light traps and biological filters to monitor and control sea lice in a commercial setting to assess the effectiveness of these methods to attract and remove adult and planktonic sea lice from a cage culture environment.

Investigations into the potential use of cunners, also known as ‘cleaner’ fish, to remove sea lice from Atlantic salmon in farm cages could provide an alternative method of sea lice control in Canada, and Newfoundland in particular.

Integrated multi-trophic aquaculture (IMTA)

From January 2010 to December 2014, researchers are studying the effects of Slice® on a sediment dweller (Clam Worm) commonly found in the Bay of Fundy at fish farms where the chemical is used in New Brunswick. Ongoing toxicity studies are assessing acute and chronic effects of the therapeutant on the worm to assess the feasibility of culturing worms under salmon farms as a means to ‘process’ the organic solids that settle out from the farms.

Researchers are examining the ability of filter-feeding shellfish species, such as blue mussel, Pacific Oyster, and Japanese Scallop, to consume the planktonic nauplii/copepodids of sea lice under laboratory conditions. If a species is identified, the research will conduct a related field experiment to determine whether bivalves grown by salmon farms could potentially reduce the abundance of sea lice on caged salmon.

Genomics in lice and salmon (GiLS)

A multi-disciplinary research team in British Columbia initiated GiLS in 2008 to achieve four key objectives: 1) clarify the genetic responses of Pacific and Atlantic salmon to L. salmonis sea lice using microarray technology to predict defense responses by both salmon; 2) uncover the genetic responses of sea lice in order to develop effective parasite treatment targets; 3) confirm and define the Pacific population of L. salmonis sea lice; and 4) analyze the use of science in understanding, and moving towards the resolution of sea lice/salmon controversy.

  • Canadian Aquaculture R&D Review articles: 2009, 2011

Treatments

To inform farm location and management practices in Knight Inlet and the Broughton Archipelago, researchers gathered information on: where sea lice larvae were located; how far and fast they spread from farm sources of adult sea lice and eggs; and how long the larvae remained present and infective after farm sources were reduced by treatment or harvest. (June 2010 – March 2011)

Laboratory and field-based research to fill the knowledge gaps concerning Slice® residues in salmon in water warmer than 5°C took place between July 2006 and March 2007 (Slice® is an in-feed sea lice treatment). This study sought to alleviate problems linked to the 68-day withdrawal period before the salmon could be cultivated that was required at the time when using the therapeutant.

An evaluation of the concentration of emamectin benzoate, the active compound in Slice®, in localized sediments and the water column as well as its effect on resident Pacific Spot Prawn populations, was undertaken in two phases. Research took place under laboratory and field conditions using a wide range of genomics-based methodologies. The study also sought to use the measured emamectin benzoate concentrations to test, calibrate and implement the DEPOMOD model to predict the behaviour of the compound in relevant aquatic ecosystems for the purpose of informing future policy regarding the use of Slice®.

Using a scale model circular cage system in the world’s largest laminar flume tank, researchers studied how rapidly therapeutants diluted/dispersed following treatment and the implications for non-target organisms within tarps and well boats. The results showed rapid dilution/dispersion of bath therapeutants in the top layers of the water column representing various grow-out conditions in Atlantic Canada, indicating that therapeutants are not expected to reach non-target organisms on the sea bed during normal treatment operating conditions.

  • Canadian Aquaculture R&D Review article: 2011

The transport and dispersal of effluents from bath and well boat treatments at multiple cage sites are being tracked using fluorescent dyes in order to estimate the volume of exposure to the marine environment, including the area of benthic exposure, followed by research on effects.

Potential effects of farmed salmon sea lice bath treatments on non-target organisms are being studied in southwest New Brunswick. Researchers will look at the effect of AlphaMax® and Salmosan® (chemicals used to treat sea lice on salmon) on larval and adult lobster and sand shrimp and will seek to understand the response of adult lobsters to repeated short-term exposures to AlphaMax® as well as to long-term exposure to low concentrations of the pesticide.  In conjunction with dye dispersion studies, water samples will be collected in the field for toxicity testing with crustaceans.  As a continuation of this project, oxidative stress biomarkers will be used to assess the sublethal and cumulative impacts of sea lice treatments (AlphaMax® and Salmosan®) on these non-target organisms. Research results could provide guidance for the development of integrated pest management plans for the salmon aquaculture industry.

Research to assess cumulative impacts of sea lice treatments (AlphaMax® [deltamethrin] and Salmosan® [azamethiphos]) on non-target organisms such as shrimp and lobster. Studies will assess the rate at which the chemicals accumulate and how much is retained in shrimp and lobster tissue. New technology allows researchers to take thin slices (cryosections) of an entire animal in order to study bioaccumulation and assess any impacts at the cellular level.

Sea lice on wild salmon

A multi-disciplinary research team is investigating the potential of sea lice as a transmitter of bacterial and/or viral pathogens to salmon hosts. The research includes a genetic examination of the salmon immune response to sea lice feeding to determine whether sea lice feeding activities promote small, localized patches of reduced immune response, which could potentially act as portals of pathogen entry.

  • Canadian Aquaculture R&D Review article: 2011

Research partners in the Broughton Archipelago Monitoring Plan seek to improve understanding of sea lice levels on juvenile wild pink and chum salmon and the interactions between sea lice, wild salmon and farmed salmon in the broader geographic area. Participants in the plan are also working to evaluate the effectiveness of different salmon farm management approaches to reduce the potential for sea lice from farmed salmon to infect juvenile Pink and Chum Salmon.

In 2007 and 2008, researchers investigated the overall health of juvenile Pink Salmon during their out-migration in the Broughton Archipelago. The fish were evaluated for physiological condition, sea lice, other parasites, bacteria, viruses and microscopic lesions. The findings suggested that the condition factor was not significantly associated with sea lice.

  • Canadian Aquaculture R&D Review article: 2009

Studies involving modeling of sea lice dispersion and encounter rates with juvenile pacific salmon, during early seawater residency and migration in the Broughton Archipelago and Discovery Islands

DFO surveillance for sea lice on wild juvenile Pink and Chum Salmon between 2003 and 2008 revealed a decline in sea lice prevalence and abundance on the salmon.

  • Canadian Aquaculture R&D Review article: 2009

Research conducted between 2007 and 2008 indicated that juvenile Pink Salmon needed to reach critical weight of 0.7 g to withstand sea lice.

To better understand the susceptibility of juvenile pacific salmon to sea lice, researchers tested the hypotheses that: 1) juvenile Pink and Chum Salmon are equally susceptible to L. salmonis sea lice; and 2) that a nutrient-deficient diet is associated with more sever L. salmonis infections. Among the findings, healthy juvenile Pink Salmon had a relatively enhanced innate resistance to this sea lice species.

  • Other findings are profiled in the Canadian Aquaculture R&D Review article: 2007
  • Related research: susceptibility to sea lice comparison between juvenile Pink and Chum Salmon to juvenile farmed Atlantic Salmon (Canadian Aquaculture R&D Review 2007).

A multi-year research project examines the effects of single and repeat sea lice (Lepeophtheirus salmonis)  infections on the health of juvenile pacific salmon of various species under laboratory conditions. Researchers are looking at the susceptibility and lethal infection level of juvenile Sockeye, Coho, and Chum Salmon to sea lice as well astheir immune responses.

The abundance of juvenile Pink and Chum Salmon in the Broughton Archipelago in July 2006 was estimated to determine if the area around salmon farms was a migration corridor or rearing area. The study also undertook to determine the health of the juvenile salmon reared in the Broughton area during that time.

  • Canadian Aquaculture R&D Review article: 2007

Discovering how and when sea lice infections develop on pacific juvenile wild salmonids following their entry into sea water is necessary in order to assess what, if any, role salmon farms play as a source of sea lice or other pathogens on the infection of juvenile wild salmon. From 2010-2013, researchers will be looking at the development of sea lice infections on juvenile Pink salmon, Chum salmon and non-salmonid hosts within the Strait of Georgia and Johnstone Strait. Levels of sea lice will be monitored from early seawater entry until the time that the fish enter Queen Charlotte Sound.

Research was undertaken between August 2004 and May 2006 to identify the sources and cycles of natural L. salmonis sea lice production in the Pacific Ocean in order to relate these cycles to the development of sea lice on salmon in net pens, and facilitate effective management of the parasite. A second, complementary study was undertaken between May 2005 and June 2007 to monitor the sea lice development on Stickleback and other possible hosts during the two months just prior to and during Pink and Chum Salmon entry into the ocean.

Examination and enumeration of sea lice on troll caught Pacific salmon in QueenCharlotteStrait.
Examination and enumeration of sea lice on troll caught Pacific salmon in Queen Charlotte Strait.
Examination and enumeration of sea lice on hook and line caught Atlantic salmon on salmon net pen site.
Examination and enumeration of sea lice on hook and line caught Atlantic salmon on salmon net pen site.

Research technologies

The feasibility of using Scottish sentinel cage technology to quantify the abundance of planktonic L. salmonis sea lice larvae during the winter months in the Broughton Archipelago (particularly during the weeks and months prior to the out-migration of juvenile Pink and Chum Salmon) was studied between December 2007 and 2009.

Modeling in support of sea lice management

Field programs and numerical circulation models developed through Fisheries and Oceans Canada research significantly increased the knowledge and understanding of the circulation of the Broughton region of British Columbia. Scientists have used particle tracking software and the numerical model currents to simulate the movement of pathogens, toxic algal blooms and planktonic larval stage of sea lice from different source locations. Researchers used the models to investigate the life history of sea lice.

Two computer models were developed for the Broughton Archipelago to be able to hindcast copepodid concentrations for 2009 to 2013. The first is a three-dimensional model capable of simulating velocity, salinity and temperature fields, and the second is a coupled model of sea lice dispersal and development/behaviour.

  • Research abstract (project 1, project 2), Canadian Aquaculture R&D Review articles: 2009, 2011
  • Fact Sheet: Modeling in Support of a Coordinated Area Management Production (CAMP) Plan for Sea Lice in British Columbia

Beginning in 2012, a predictive model is being developed of the distribution of sea lice originating from fish farms, to estimate the number of encounters of out-migrating salmon with sea lice.

Related initiatives and links

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