Utilization of the Cunner (Tautogolabrus adspersus), a Wrasse, as a Means of Sea Lice Removal in Commercial Salmon Farms

Final Report

Kelly Cove Salmon Ltd.

AIMAP 2011-M03

Executive Summary

With the global demand for seafood rising and wild fish populations either leveling off or declining, aquaculture, including salmon farming, is becoming an increasingly important part of the world's food supply. Salmon farmers in Atlantic Canada and Maine can be important contributors. However, those farmers and their veterinarians need access to adequate management tools to protect the health and welfare of the animals in their care.

Sea lice (Lepeoptherius salmonis) are naturally-occurring ectoparasites that can, if left unchecked, have a serious impact on farmed salmon. Farmers in Atlantic Canada and Maine have struggled since the late 1990s to manage naturally-occurring sea lice on their farms without the same treatment tools that are approved in other countries. In spite of the development of Integrated Pest Management Plans (IPMP), both in Canada and the US, farmers are not able to implement these plans because they lack treatment options. IPMPs combine farm management practices with access to a variety of approved treatments that farmers can use strategically to target various life stages of sea lice while considering complex environmental factors, including local conditions, water temperature and size of fish. Effective IPMPs allow farmers to use the right product at the right time, thus reducing the overall amount of treatment used while keeping lice numbers at an acceptable low level.

An important aspect of an Integrated Pest Management Plan is the deployment of cleaner fish –natural predators of sea lice that can co-exist with salmon and help reduce sea lice numbers.

The rationale for this project therefore, is to investigate the effectiveness of a wrasse or cleaner fish as an alternative, non-chemical technique of removing sea lice from farmed Atlantic salmon.

The goal of this project was to determine the usefulness of the cunner as a commercial means of controlling sea lice in commercial salmon farms in Atlantic Canada. The objectives were 1. To study (observe and document) the behaviour of cunners and their interactions with salmon and vice versa, and to determine if cunners will consume formulated feed pellets (feed preference tests) through tank trials and 2. To test the effectiveness of cunners as a cleaner fish through field trials using commercial sea cages.

In repeated feed preference trials conducted under Objective 1, cunners showed no interest in formulated feed pellets of any size utilized in all stages of the salmon life cycle and neither salmon nor cunners showed any adverse reaction to the presence of the other.

In field trials using commercial sea cages under Objective 2, three stages of sea lice (Chalimus, Pre-adult and Gravids) were monitored through weekly counts throughout the trials and cunners showed the greatest impact in reducing the levels of gravid stages (when compared to the other two life stages), thus demonstrating that cunners are effective at removing at least one (critical) life stage of the sea lice from salmon in sea cages. Removing the gravids is critical because it represents a vital break in the life cycle of the sea lice. It is also the larger adult stages that cause damage to the salmon and these are selected by the cunners as preferential feed.

The next step in developing the cunner as a commercially-viable cleaner fish component of an IPMP will be to develop a breeding program so the farmed salmon industry will not have to rely on a supply of wild cunner for sea lice control.

1. Introduction/Background

Control of sea lice among populations of farmed Atlantic salmon has been an issue for the industry since its inception in Norway about 30 years ago. Sea lice are ectoparasites commonly found among wild Atlantic salmon but generally do not appear to harm the fish due to the low abundance of wild salmon relative to the ocean migration zones. To date the reservoir for sea lice is unknown, although they have been reported to occur on other fish, including species of clupeids. The likelihood of heavier infections is increased in an aquaculture setting. This type of increased rate of infection is not isolated to salmon farming but also occurs in plants, birds and mammals that are grown intensively.

With growth in the salmon farming industry, and the more recent increases in coastal water temperatures, the frequency and severity of sea lice infections has increased to a point where companies need to use an array of therapeutants in combination with improved management techniques (e.g., rotational Bay Management Areas and fallowing) to control infections. Traditionally, most sea lice therapeutants have been applied either as an in-feed product or through bath treatments where a tarpaulin is utilized in order to control dosage, or the fish were pumped into the hold of a well boat where the dosage could also be controlled.

Competing salmon farming nations including Norway, Scotland and Chile have access to a broad array of approved sea lice therapeutants but Canada as yet, has access to very few, and some of those only through Emergency Registration as pharmaceutical companies work towards gaining full registration for these products. Moreover, with limited treatment options, some of the therapeutants are becoming less effective the more they are used. Salmon farmers believe sea lice can be controlled without impacting the marine environment if they have access to the most effective tools.

While gaining access to an expanded array of approved products is an important initiative of Canada's salmon farming industry, there are also other initiatives aimed at developing non- therapeutant means of controlling sea lice. All of these means taken together comprise the Integrated Pest Management Plan (IPMP) being developed and implemented by industry-government working groups.

Researchers at Kelly Cove Salmon Ltd. (KCS) have been investigating alternate and novel approaches to sea lice control as a means to complement the in-feed and bath treatments currently available. Our company believes that an IPMP approach represents the way forward so that the industry has a multi-pronged strategy of treatment options.

The rationale for this project therefore, is to investigate the effectiveness of a wrasse or cleaner fish as a possible technique to remove sea lice from farmed Atlantic salmon. Research and use of wrasse in the Norwegian salmon farming industry has been ongoing for the past 20 years, but recently there has been increased interest in further developing this approach because of the reduced efficacy of the in-feed treatment emamectin benzoate, commonly known by the brand name Slice®. The species of wrasse in Norway that are being researched and/or used by the industry are the Goldsinny, Corkwing, Cuckoo, Rock Cook and the Ballan Wrasse. Each of these has different merits making them all interesting candidates to the Norwegian industry. Kvenseth et al (2002) demonstrated the effectiveness of wrasse at a commercial farm owned by Villa Organic with 450,000 salmon and wrasse stocked at 4%. During the course of the trial the farm experienced repeated infestations with sea lice but every time the wrasse kept the sea lice numbers under control not allowing the lice to reach sexual maturity. One advantage of using wrasse is the fact that they can maintain “continuous control” of the lice while they are in cages rather than the periodic control seen with other types of treatments. It is estimated that 20% of the salmon farms in Norway are now using some wrasse for sea lice control.

Unfortunately, none of the wrasse species used in Norway is native to Atlantic Canada. This required us to consider a different species - the cunner (Tautogolabrus adspersus). Although a different species from those used in Norway, it is important to note that the cunner is from the same family as the Norwegian cleaner fish: Labridae (the wrasses). The cunner is often seen around wharf pilings in shallow water areas in Atlantic Canada and is known to be a scavenger fish, feeding on a variety of organisms including molluscs, crustaceans, sea urchins, marine worms, fish eggs, and eel grass. Cunners are known to mature at sizes of 8-11 cm in length and may live for 7 years reaching maximum sizes of ~ 40 cm. Studies in Norway with different wrasse species suggest ratios of approximately 3 - 4% but this will need to be established for the cunners in Atlantic Canada.

Preliminary work on the efficacy of the cunner in a laboratory environment completed by KCS during the summer of 2010 verified that cunners are effective at removing sea lice from infected salmon. This work was carried out in tank trials with wild-caught cunners and salmon infected with sea lice. Video footage of the cunner-salmon interaction was taken over multiple days. The cleaning or grazing ability of the cunners was determined by counting the number of lice on the salmon before introducing cunners and counting the number of lice on the salmon after 24hr, 48hr, 72hr etc. after introduction of the cunners. An earlier trial with cunners by MacKinnon (1995) also established the fact that cunners consumed sea lice from infected salmon under experimental conditions in tanks. With this positive outcome established by the proof of concept studies conducted at the Huntsman Marine Sciences Laboratory, KCS proceeded to the next phase of research to determine whether cunners are a viable option as a cleaner fish in a commercial salmon cage site setting and to determine if cunners would show any preference for formulated feed when fed to the salmon in sea cages.

2. Objectives and Deliverables

The following are the objectives and deliverables of the project:

1. Tank Trials:
   
   To conduct tank trials designed as a follow-up to experiments conducted by KCS in 2010, this time to study (observe and document) the behaviour of cunners and their interactions with salmon and vice versa, and to determine if cunners would consume feed pellets, moist feed and/or fouling organisms typically found on sea cage nets (feed preference tests).
   
   
2. Field trials in Sea Cages:
   
   To conduct field trials with cunners in sea cages to determine if cunners are effective at removing sea lice under commercial salmon farming conditions and to determine the optimum ratio of cunners to salmon for effective sea lice control.

3. Methodology

i) Tank Trials

Cunners were transferred via truck from the L & J cage site (spare cage) into 1,600L tanks at the Huntsman Marine Science Center (HMSC) on Dec 5, 2011. Four High Definition (HD) underwater cameras were purchased and fitted into the four 1,600L experimental tanks on Dec 2, 2011. Cunners were initially placed in holding tanks at the BioCenter building at the HMSC and allowed to acclimate for three days before they were transferred to the experimental tanks. In order to ensure that the protocol developed for these feed preference and behaviour trials will be feasible, a "dry run" was completed on Nov 10, 2011. As a result, some modifications were made to the protocol which included selecting a specific feed size and repeating the trials five times to get a reasonable number of sample size (n). Actual feed preference and behaviour trials were completed over two days from Dec 13 to 14, 2011 with participation of Dr. Shawn Robinson of the St. Andrews Biological Station (SABS, DFO) on Day 1 of the two days.

Two experimental tanks held 10 cunners (4 small, 3 medium and 3 large fish) each with no salmon and another two experimental tanks held 10 cunners (mixed sizes) and 10 salmon (~1.6 kg each). Cunners were visually graded into the three size groups based on relative sizes of available fish prior to the trials. The types of food tested were as follows:

1. A 1 m section of rope heavily fouled with typical fouling organisms on cage sites including significant amount of mussels (to represent grazing on net foulants) obtained by Dr. S. Robinson's technical group,
2. Shucked whole mussel meat,
3. Salmon feed pellet sizes that would potentially be used to feed salmon in sea cages i.e., 3.5 mm, 5.0 mm, 6.5 mm and 10.0 mm.

The rope with foulants and mussels was placed in each tank just prior to offering feed pellets to the fish. Two pellets at a time were presented to the fish, waiting till the pellets reach the bottom of the tank before dropping the next two pellets for a total of 20 pellets, then left for 2-3 minutes before siphoning off the uneaten pellets. This feed preference and behaviour trials were completed over two days from Dec 13 to Dec 14, 2011 and all trials were recorded on HD PVR (video recorder).

To make sure that the cunners showed no interest in the feed pellet because they were not hungry, we substituted pellets on the fourth trial with mussel meat and in every substitution with mussels; all the cunners attacked and consumed all the mussels vigorously.

ii) Field trials

Sea cage trials at L & J marine site were late getting started so data on low to medium infestation timeline was not collectable. The project was, therefore, extended to Oct 2012 with data and results reported as Part I and Part II.

Field trial Part I (Sept 1, 2011 to Mar 31, 2012)

The original plan was to have the project started in June or July 2011 while sea lice levels were relatively low and water temperatures were rising. This would give the best opportunity for the cunner effectiveness to be tested as they encounter low sea lice levels in the beginning, giving them a chance to “learn” to graze on the sea lice. This would likely give the cunners an opportunity to keep ahead of the increasing sea lice levels. However, by the time the project commenced, sea lice numbers on fish at the site had reached a very high level resulting in the need to treat the salmon with Salmosan (azamethiphos) and Interox Paramove 50 (hydrogen peroxide) prior to cunner stocking. The first treatment was done on Sept 19, 2011 with Salmosan. This was followed approximately one month later by another treatment with Interox and then a third treatment on Dec 11, 2011 also with Interox.

A total of 36,800 salmon of approximately 2 kg were transferred to the 20 experimental cages at L&J site in Aug 2011, evenly stocked at 4,800 salmon per cage. Smolt nets measuring 12 m x 12 m x 7 m deep were installed in a two-row steel cage system. Salmon were initially fed 5 mm Signature Salmon feed with size increases to 6.5 mm in Sept 2011, 7.5 mm in Mar 2012 and finally 10 mm in June 2012, fed to satiation twice daily while waiting for permits to collect and transfer cunners were approved.

Evergreen Fisheries Inc. (Evergreen Fisheries), a commercial fishing company from Digby, Nova Scotia was contracted for the collection of wild cunners and samples of cunners were taken for health testing in Sept 2011. Test results were obtained, submitted and approved by the New Brunswick Department of Agriculture, Aquaculture and Fisheries (NBDAAF), which subsequently gave approval to commence collection on Oct 17, 2011. As per DFO requirement, Javitech/GTA was contracted to provide scientific training to Evergreen Fisheries personnel with regards to data collection before Evergreen Fisheries could commence fishing. Data on catch and by-catch, GPS locations, haul times, etc. were collected by Evergreen Fisheries and submitted to Javitech/GT to be entered into a DFO database.

Cunners were successfully caught in traps by Evergreen Fisheries from the Bay of Fundy and transferred to the L & J marine cage site on Oct 23, 2011. Cunners were stocked into respective cages (eight 12m x 12 m x 7m cages; stocked with ~4,600 salmon; two replicates per treatment condition i.e., two cages at 0% cunners (Control cages), 3% cunners, 6% cunners and 9% cunners in relation to salmon) and the trial commenced in early Nov 2011.

Mort dives were conducted weekly with two divers taking approximately one hour to complete the work. Salmon weights were usually projected by computer program but were occasionally sampled using Vicass to more accurately revise projections. Weights were also obtained during lice treatments.

Sea lice counts on the salmon began prior to introduction of the cunners in order to establish baseline levels and this counting was continued on a weekly basis through the late summer and fall seasons. Salmon and cunners were monitored with respect to mortalities on a weekly basis and entered into KCS database software called Farm Control (now known as Fish Talk). All data would be compiled and reported in the final project report (Oct 2012). Lice counts were done every Tuesday, primarily by Atlantic Veterinary College (AVC) technicians. Counts were usually done by two counters and one data transcriber with each session taking about two hours. A total of ten fish from each cage was randomly sampled.

Approximately 200 cunners (the replacement cunners) were kept in a spare cage to be used to replace any mortality suffered by any cunners in the trial cages and were fed crushed mussels on a weekly basis. They were also observed to feed on biofoulants on the net. The low mortality rate (<1%) during Part 1 of this trial and the relatively small number of cunners employed per cage meant replacing them was infrequent and was usually achieved by divers catching them in bags and then transporting the appropriate number to any cage that needed replacements for mortalities.

Field trial Part 2 (Apr 1, 2012 to Oct 31, 2012)

Given the late start in 2011, cunners in the trial cages were held over through the winter in order to continue the trial through the summer of 2012, extending the AIMAP project to Sept 30, 2012. This would provide a more complete data set and permit making a more realistic assessment of the efficacy of the cunners at removing sea lice from salmon. The cunners survived the winter well in the trial cages at L&J but all mortalities had to be replaced to make sure that the per cent inclusion rates remained true to the original ratios at the start of this trial.

The following protocols were included in Part 2 of the project during the extension:

1. To replace any mortality suffered by cunners, more cunners were added to “top up” the cages on July 27, 2012.
2. The ratio of cunners to salmon in the two cages that had 6% cunners were also changed to 12% to determine if putting a higher percentage of cunners in sea cages would make any difference in efficacy of cunners at removing sea lice from salmon.

There was no interruption of activities associated with this extended phase of the trials from the original start date till fish were harvested. For the period from Apr 1, 2012 to Sept 20,
2012 when fish were harvested, lice counts were done by one technician from the KCS Fish Health team which took about three hours, although counters from AVC continued to do pre and post treatment counts.

As in the original period of this project (Part 1), the salmon also had to be treated, this time probably influenced by an influx of sea lice from a salmon farm that was owned by a different salmon farming company and located 300-400 m away from L&J where no apparent remedial action had been taken to treat the sea lice infestation at the site perhaps because fish were of market size and may have been actively harvested during most of the experimental period. It was therefore, necessary for KCS to treat all experimental fish at L&J on multiple occasions as follows: May 10 and 30, 2012 (treatment was split ½ site each time because of availability of well boat); July 16 to 17 2012; and Aug 18 to 19, 2012 (all with Interox). Prior to treatments with Salmosan and Interox during this field trial, the potential impacts of these treatments on cunners were tested in the laboratory by DFO senior scientist, Dr. Les Burridge. Dr. Burridge's results showed no negative impact of Salmosan and Interox (at commercial treatment concentrations) on the cunners.

Daily activities, other than the twice daily feedings, consisted of general site maintenance, observing biosecurity protocols and data collection (temperature, dissolved oxygen level, etc.) plus weekly activities such as feed reception and distribution, mort dives and lice counts. Nets had to be kept free of biofoulants to make sure that cunners do not feed on them instead of sea lice. This was achieved by divers washing the nets with pressure washers and by changing nets when necessary.

4. Analysis and Discussions of Results

i) Tank trials

Results from the tank trials (feed preference trials) were as follows:

1. Observations made by teams from both KCS (Dr. K.P. Ang, Mindy Harrison, RJ Wilson and Christie Nelson) and DFO (Dr. S. Robinson) indicated that neither the cunners nor salmon showed any irritability or aversion/avoidance signs when placed together in the same experimental tanks.
2. In fact, cunners behaved positively in the presence of salmon, choosing to swim underneath individual salmon as they move in unison (at times) and alternating between the salmon, the underwater cameras and sections of the PVC pipe as shelters.
3. In trials conducted over two days at the HMSC, the cunners showed no interest (0 positive response) toward any size of commercial formulated feed pellet offered to them whether in the presence of salmon or not so no statistical tests were necessary at this point.
4. None of the salmon showed much interest in the feed either so we offered the same pellets to a different group of salmon in another tank and fish in those tanks readily consumed the pellets (for all sizes of pellets tested). Technicians for this project confirmed that the salmon used in these trials have not been feeding well even prior to their transfer to these experimental tanks.

ii) Field Trials

Part 1

The late start date in 2011 did not allow for a full assessment of cunner effectiveness as sea lice levels were very high at project start and the decreasing late fall water temperatures likely impacted cunner activity. As mentioned, the high levels of sea lice prior to the introduction of cunners unfortunately, meant that we had to treat with both Salmosan and Interox prior to cunner stocking.

An evaluation of the performance of cunners as a cleaner fish has been made for periods from Nov 10 to Nov 30, 2011 and again for a shorter period of Nov 30 to Dec 7, 2011. Data on percent increase or decrease in lice levels of all stages were variable in all cages (both treatment and control). However, it is encouraging to see that for the period from Nov 10 to Nov 30, 2012, fish in several of the cages that included cunners actually had reductions in pre-adult lice levels ranging from -4% to -37% while both control cages saw increase in pre-adult levels of 6% and 56%. Also, despite the fact that fish in all experimental cages at L&J had increased levels of gravids, this increase in number of gravids was much less for fish in cages with cunners (with the exception of cage 23) than the increases for fish in the control cages (365% and 315%). The levels of gravids would be a better criterion for determining the effectiveness of cunners because the cunners would feed more easily on adults/gravids due to the larger particle size but both the chalimus and pre-adults levels would be consequences of gravid removal (or recruitment).

For the second period (Nov 30 to Dec 7, 2011), fish in all experimental cages still had similar variability in lice levels but overall, lice levels had not changed much (with the exception of a couple of cages) from the start to end of this shorter period in most of the control and treatment cages. This can probably be explained by the decrease in cunner activity due to the lower water temperature for this period and/or little change in lice levels as the infestation rate naturally slows down with the drop in water temperatures (any pronounced increase or decrease in levels could also be an artifact of sampling accuracy for such a short period). In general, most of the cunners survived through the winter and there have been no adverse effects of the cunners on the salmon population.

Part 2 (Extension)

For Part 2, with more data points obtained during the extended trial period, the analyses could be simplified by reviewing the trends in the levels of different life stages of sea lice and could be described in the following statements. The trial ended when the level of sea lice on the experimental fish was determined to be potentially detrimental to the health/welfare of the salmon as determined by NBDAAF on Sept 13, 2012 following their site inspection and review.

The results are summarized below, based on the level of the three stages of sea lice recorded at each lice count, namely, the Chalimus stage, the Pre-adult stage and the Gravid stage:

1. There was no apparent effectiveness of cunners in affecting the levels of the chalimus stage of the sea lice on salmon because the particle size of chalimus is physically too small for cunners to consume. It is unclear why the levels of chalimus on salmon in treatment cages were higher than those on salmon in control cages but tidal flow patterns and cage location may have some influence.
2. There was no difference in the trends for the pre-adult stages of sea lice on salmon in both treatment and control cages, increasing and decreasing almost in unison. The particle size for the pre-adult stages are starting to be large enough for cunners to consume but this rate of removal is probably lower than the overwhelming rate of chalimus recruitment from external sources which then develops into pre-adults, thus masking any apparent difference in infestation levels.
3. The most pronounced difference in trends seen during this phase of the trials can be found in the gravid stages. Without the influence of cunners, pre-adults develop into gravids and numbers stay unchecked on salmon in the control cages (reaching more than twice the levels on salmon in treatment cages) while gravids that develop from pre-adults on salmon in the treatment cages were controlled or consumed by cunners keeping the numbers lower than on salmon in the controls. This trend also supports earlier observations in the laboratory where cunners were seen to readily consume the larger size pre-adults and gravids.

This trend should probably be reviewed in association with the following:

• The gravids are the most easily consumed stage of the lice (being the largest particle size and from personal observation, there seem to be a preference by cunners for egg strings).
• The removal of gravids in an environment where there is no pronounced or reduced influx of sea lice from outside sources should have resulted in a corresponding drop in chalimus and therefore, pre-adult stages because the level of one stage of the life-cycle of the lice (gravids) have been drastically reduced i.e. reduced amount/level of eggs should result in reduced level of larva and therefore, result in reduced level of chalimus stages, etc. (although under normal circumstances, there will always be some level of recruitment from external sources). Unfortunately, during this trial, there was a constant recruitment of motile lice stages from an untreated lice infected farm located 300-400m away. This result probably best demonstrates the need to have a protocol requiring that all sites in the same Bay Management Area (or tidal influence) be treated at the same time.
• The fact that the cunners were able to remove gravid lice despite the constant recruitment of lice probably attests to or confirms the high efficiency of the cunners at removing sea lice from salmon.
• The decrease in levels of gravids (and pre-adult stages) in both the treatment and control cages seemingly prior to each treatment is explained by the protocol of counting lice before and after treatment.

4. Finally, it is not apparent which ratio of cunners to salmon (3%, 6%, 9% or 12%) worked best or was optimum because of the highly variable data which could have been a result of interference/recruitment from external sources of lice, etc. but putting 9% or 12% of cunners in a cage may not be economically viable or sustainable.

5. Communication

KCS plans to communicate the results of this research in the following manner:

1. Publishing the results of this project in the next issue of the Cooke Aquaculture newsletter (Spring, 2013) which is distributed widely among industry peers, university and government personnel.
2. In the annual Canadian Aquaculture R&D Review.
3. Presentation at the AAC 2013 in Guelph in June 2013.
4. Internal workshops in Chile in 2013.

6. Benefits

The success of the cunners as a cleaner fish will have a significant regional impact in Atlantic Canada and Maine in terms of a new, sustainable measure for combating sea lice infections because it is a native species in all these waters from NL to Massachusetts and the protocols developed are easily transferable to the entire region and possibly to the West Coast of Canada. Although there are no cunners on the West Coast of Canada there are other species of fish such as the three spine stickleback which have been shown to actively graze on sea lice attached to salmon. It is probable that practices developed here on the East Coast will be easily transferrable to “new” wrasse species on the West Coast.

KCS is hopeful that cunners will be approved as a commercial means for controlling sea lice in salmon farms and thus be added to the set of existing tools in our Integrated Pest Management Plan (IPMP) toolbox for the treatment and control of sea lice in our salmon farms in New Brunswick and eventually for the rest of Canada.

Industry-government working groups are developing and implementing an Integrated Pest Management Plan (IPMP) to control the frequency and intensity of infections. The IPMP includes in-feed and bath treatments with various classes of therapeutants. The IPMP also includes non-medicinal treatment methods, one of which is the use of “cleaner fish” which feed on the sea lice (biological). This project demonstrated the strong potential for a local species of cleaner fish, the cunner (Tautogolabrus adspersus), to remove sea lice from farmed Atlantic salmon.

7. Conclusions and next steps

1. Tank trials:
2. Cunners tested at the HMSC showed no preference whatsoever to commercial formulated feeds (of any size) that are normally used to feed salmon in sea cages (0 positive response to pellets offered) and
3. Cunners behaved positively to the presence of salmon and showed no signs of aversion or avoidance to salmon, choosing instead to swim underneath individual salmon as they move in unison (at times) in between using the cameras and the stand pipe as shelters.

1. Field Trials:

Part 1. Original AIMAP project schedule (Sept 1, 2011 to Mar 31, 2012)

1. Results from the original sea cage trials while promising, were inconclusive so the project was extended to Oct 31, 2012.

Part 2. Project extension period (Apr 1, 2012 to Oct 31, 2012)

1. Cunners were effective at removing the gravid stage of the lice from salmon.
2. The cunners preferred to stay deep and hide among the artificial kelp made from strips of heavy plastic sheets placed in the cages, so were seldom seen at the surface but have been observed both with the naked eye and through cameras to actively feed on the sea lice infecting the salmon (personal observations by site manager and crew of L&J).

The next step in the development of cunners as a relatively new (to Canada), non-chemical sea lice treatment technology will be to develop a breeding program to produce cunners from captivity for the farms so that the need for wild sources can be reduced well before it starts to impact the sustainability of using this species from the wild (and potential threat of over-fishing).

8. Acknowledgements

This project was partially funded by DFO-AIMAP program (regional Maritimes assistance from C. Webster, C. Dale, C. Reynolds) and NBDAAF (B. Hill). We are most grateful for these funding support and for the support we have received from DFO for the transfer permits (J. Cline), scientific licences (C. Farr, V. Docherty, P. Hurley); to NBDAAF for the disease screening (Dr. M. Beattie) and amendments to the site licence to include cunners (K. Coombs, G. Smith); to DFO SABS for participating in the feed preference tank trials (Dr. S. Robinson) and for conducting laboratory trials to investigate the potential impacts of Salmosan and Interox on cunners (Dr. L. Burridge); to the dedicated lice counters of Atlantic Veterinary College; to F. Powell (project team member at start); to S. McGrattan for coordinating the well boat treatments and to the KCS fish health team (Dr. L. Hawkins, Dr. S. Fielding, E. Gagne) for conducting and coordinating the fish health testing requirements; to the Manager and crew of L&J (L. Dickinson -site manager); to our Research Technicians in the lab/hatchery (M. Harrison, R.J. Wilson and C. Nelson); to Evergreen Fisheries Inc. (S. and B. Newman) for collecting the cunners and to our communication team (N. Halse and C. Brown) for reviewing this manuscript.

9. References

Kvenseth, P.G., Andreassen, J., og Bergh, Ø. 2002. Leppefisk – liten rensefisk kan berge stor laks!.I: Glette, J., van der Meeren,T., Olsen, R.E. og Skilbrei, O. (red), 2002 Havbruksrapport
2002. Fisken og havet, særnr. 3-2002.

MacKinnon, B.M., 1995. The poor potential of cunner, Tautogolabrus adspersus, to act as a cleaner fish in removing sea lice (Caligus elongates) from farmed salmon in Eastern Canada. CJFAS 52-1 175-177.