Caligus5

A newsletter on the biology and control of sea lice distributed free to researchers,aquaculture and fisheries industry, educators, consultants, and managementauthorities.
This fifth issue of
4th International Conference on Sea Lice
Caligus includes:
28th-30th June 1998, Trinity College, Dublin, Ireland Articles
Theme
The 3rd international conference held in Amsterdam in 1998 focused on
sea lice biology. This meeting will thus focus on applied aspects of • progress and future options for vaccines • Integrated Lice Management strategies • lice population dynamics, including production, dispersal, Research Projects
transmission between farms and between farms and wild fish.
Deadlines
Submission of abstracts
Accomodation
A limited number of rooms has been booked in good quality accomodation in Trinity College, Dublin. This is the most convenientplace to stay for the conference, is in the city centre and is half the price of hotels and guesthouses. When these rooms are full, delegates will have to make their own arrangements for accommodation. Rooms will only be reserved for named persons on payment of costs.
Reports and News
*All rooms have access to a kitchen if people want to make their own Abstract Submission
Offers of papers must be submitted by 26th February 1999. Final versions of abstracts are required by 31st March 1999. All peoplepresenting papers must pre-pay their registration fee.
Standard guidelines for the presentation of posters and talks and Conference website:http://www.ecoserve.ie/projects/sealice/meetings.html Wrasse – do they transfer diseases to salmon?
Department of Fisheries and Marine Biology, University of Bergen, Norway INTRODUCTION
Being in close contact with salmon in netpens, feeding partly from their mucus layer or on lice filledwith salmon blood, as well as on the carcasses of dead salmon, wrasse would be likely to contractpathogens present in the salmon population. Given the wrasses ability to escape from salmon pens,diseases could be spread to wild wrasse populations, or to new salmon farms with subsequent capture ofescaped wrasse.
Likewise the possibility of introducing new pathogens to salmon farming, by stocking wild wrasse with an unknown history of disease, has been a concern of the salmon farming industry. In some areasthis has hindered the commercial use of wrasse as delousers.
This article summarizes the results from a three-year project on wrasse health, including screening of wild wrasse populations, the role of wrasse as a vector for diseases, and the prevention and treatment ofdiseases in wrasse. The goldsinny (Ctenolabrus rupestris) was chosen as a model, as it is the speciesmost frequently used as a delouser in salmon farms.
DISEASES OF WILD WRASSE
Parasites
A goldsinny population from the western part of Only parasites with a direct life cycle, which Norway was sampled every second month from might be transferred from wrasse to salmon February to November. Simultaneously fish from potential problem in salmon farming. In this transferred to a salmon farm was sampled. For each population and sample date 30 fish were trichodinids on the gills of the goldsinny. The examined immediately after transfer to the trichodinids did not cause any pathogenicity, even laboratory, and another 30 were put into a latent in the most heavily infected goldsinnys, and carrier test. The goldsinny was screened for seemed to be species specific for wrasse. The presence of bacterial diseases, IPN-virus and screening of the parasite fauna was done as a Solberg (Dept. of Fisheries and Marine Biology, goldsinny gave no cytopatic effect on CHSE- WRASSE AS A POSSIBLE VECTOR OF
cells. The CHSE-cells, however, will only DISEASES
sustain growth of a limited number of viruses, so Infectious Salmon Anemia (ISA)
the presence of “new” viruses in goldsinny can This viral disease causes mortality and clinical not be ruled out by this screening. There is no signs of disease mainly in farmed Atlantic salmon evidence from the literature that wild wrasse (Salmo salar), but sea trout (Salmo trutta) carry viruses, but experiments have shown that (Nylund and Jacobsen, 1995), rainbow trout goldsinny are susceptible to IPNV (Gibson and (Oncorhynchus mykiss) (Nylund et al., 1997) and herring (Clupea harengus) (Nylund, unpublished) Bacteria
have proved to be asymptomatic carriers with the Examination of freshly caught goldsinny from the ability to transfer ISA to healthy salmon. To wild revealed no external or internal signs of either confirm or rule out the wrasse as a possible bacterial diseases, and pathogenic bacteria could not be isolated from the kidney. After the Latent Carrier test the picture was completely altered. In Blood from salmon positive for ISA, from natural one particular sample a maximum of 33 % of the outbreaks and from earlier transmission trials, goldsinny were found to have covert infections of an atypical Aeromonas salmonicida (June-96), while the common incidence was 6-10%.
2 x 30 goldsinny cohabiting with 5 ISA-injected Atypical and classical furunculosis
As wild wrasse may carry an atypical variant of 2 x 30 salmon cohabiting with 5 ISA-injected Aeromonas salmonicida it is of great importance to find out if this bacteria may be transmitted to, 30 goldsinny injected with HBSS (negative and cause disease in, salmon. Earlier work have demonstrated that wrasse are susceptible to 30 untreated salmon kept with 5 untreated classical furunculosis from salmon, both in laboratory experiments (Bricknell et al., 1996) 30 salmon injected with ISA (positive control).
and in a farming situation (Hjeltnes et al., 1992).
From all treatment groups, and from goldsinny In a laboratory experiment, groups of 2 x 30 negative control, five fish were taken out for goldsinny wrasse and Atlantic salmon were examination every fifth day from day five until intraperitonally injected with “high” day forty after infection. Moribund fish were (107CFU/fish) and “low” (105CFU/fish) doses of taken out for examination on a daily basis. All Aeromonas salmonicida subsp. salmonicida from fish were examined externally and internally for salmon or atypical Aeromonas salmonicida from clinical signs of disease. Blood samples were taken for determination of hematocrit. Tissue In salmon injected with a “low” dose of samples from several organs was fixed for Aeromonas salmonicida subsp. salmonicida examination in light and electron microscope, and mortality started at day three and reached 100 % frozen for later immunohistology. From the ISA- within day eight post-injection. In the salmon injected goldsinny blood and tissue was frozen groups injected with the atypical variant there for later re-infection experiments with salmon.
was no mortality, and sequential examination of While mortality started on day 17 and ceased fish showed no signs of disease. The experiment on day 28 (90% mortality) in the ISA injected gave no indications that the atypical furunculosis salmon, there were no mortality in the goldsinny from wrasse could be transmitted to salmon, injected with ISA, in goldsinny cohabiting with which corresponds to the findings of Costello et injected salmon, or in salmon cohabiting with injected goldsinny. Neither were there any In the goldsinny groups injected with “high clinical signs of disease or drop in hematocrit in doses” the mortalities for both isolates reached these groups. Samples of tissue processed for about 80 % within 15 days. In thewhile in the light microscopy or for immunohistology did not “low dose” groups mortalities were a bit higher in show any signs of tissue damage, or positive the atypical group (45 %) than in the classical reaction for the presence of ISA Virus.
group (35 %). When given an intraperitoneal In the re-infection experiment blood and tissue taken from the ISA-injected goldsinny (day 5, 10, susceptible to classical furunculosis from salmon 15, 20, 25, 30, 35 and 40) was prepared and as to atypical furunculosis from wrasse. This intraperitoneal injected into eight groups of implies that under farming situations with healthy salmon. There were no mortality in any classical furunculosis present in the salmon groups of salmon, neither clinical signs of disease population the use of goldsinny as cleaner fish or drop in hematocrit in salmon sampled from should be avoided, because of the risk of these groups. In a positive control group of mortalities in the wrasse and spreading the The conclusion from the experiments must be Prevention and treatment of atypical
that it is highly unlikely that goldsinny will be furunculosis in wrasse
able to transfer ISA to or between salmon groups Vaccine trials
under natural conditions. The virus does not Preliminary trials with vaccination of freshly seem to be able to establish an infection in caught goldsinny in April-May demonstrated the goldsinny, and through the cohabitation trials the problems with vaccinating a carrier population.
role of goldsinny as a possible passive vector The stress of handling was sufficient to cause an At present all material from the experimental goldsinny, and from 400 fish ip injected with an groups, frozen and stored in liquid nitrogen, are commercial oil-based triple-vaccine only 50% being screened by the use of PCR, to examine survived the five-week long immunization period.
clearance rate and possible traces of ISA- virus inthe samples.
A following challenge with atypical and classical furunculosis proved to be rather inconclusive.
chemotherapeutics to wild-caught goldsinny via the oral route, but even though ip. injection is vaccinated in December with an oil-based trial quite labor-intensive it will reduce the amount of vaccine made of formaldehyde-killed atypical antibiotics used and thereby spare both costs and Aeromonas salmonicida bacteria. As goldsinny are scarcely available in early spring, when the 100,000 smolts using 5,000 goldsinny (1: 20) will salmon smolts are put to sea, trials with winter- need 250 ml Aquacycline ¨ vet., or 12.5 g storage of goldsinny have been conducted.
Oxytetracycline. Further investigation will Simultaneous vaccination would give several probably show that the dose could be further advantages with the possibility of disease outbreaks being lower during the winter months, CONCLUSIONS
lower social interactions between the goldsinny, The screening of a goldsinny population from the and a much longer immunization period (5-6 pathogens that should pose an threat to salmon reaction caused by low water temperatures.
farming, neither were the goldsinny able to transmit ISA or atypical furunculosis to salmon.
promising results as mortalities in vaccinated The main problem seems to be the mortality in group receiving subsequent handling-stress was the goldsinny, caused by stress-induced outbreaks significantly lower than in unvaccinated groups.
of atypical furunculosis, after transfer to netpens.
Challenge experiments with ip injection of This disease may be treated efficaciously by atypical Aeromonas salmonicida however failed injection of Oxytetracycline. Vaccination of to demonstrate any effect of vaccination, but this goldsinny is difficult when the population method for challenge may be unsuitable.
contains carriers with covert infections, but Treatment with antibiotics
vaccination combined with winter-storage has Given the high mortality caused by stress-induced outbreaks of atypical furunculosis and the REFERENCES
difficulties in vaccinating the fish, a more Bricknell, I.R., Bruno, D.W. and Stone, J., 1996. Aeromonas applicable approach to reduce mortality could be salmonicida infectivity studies in goldsinny wrasse,Ctenolabrus rupestris. Journal of Fish Diseases, 19: 469- treatment with antibiotics. An experiment using three different antibiotics to treat a natural Costello, M., Deady, S., Pike, A. and Fives, J., 1994.
outbreak of atypical furunculosis was therefore Parasites and diseases of wrasse (Labridae) being used as conducted in the laboratory. Three antibiotics cleaner-fish on salmon farms in Ireland and Scotland. In were chosen on the basis of sensitivity studies of Wrasse –Biology and use in Aquaculture, Sayer, M.D.J.,Treasurer, J.W. Costello, M.J. (Eds.), pp: 211 – Gibson, D.R. and Sommerville, C., 1996. The potential for caused by atypical furunculosis started. For each viral problems related to the use of wrasse (Labridae) in treatment 2x55 fish was used. Fish in two groups the farming of Atlantic salmon. In Wrasse –Biology anduse in Aquaculture (Sayer, M.D.J., Treasurer, J.W. and were ip. injected with 0.5 ml Tribrissen ¨vet. (400 Costello, M.J., eds.), pp: 240 - 246. Oxford: Fishing mg/ml Sulfadiazine – 80 mg/ml Trimethoprim), and two with 0.5 ml Aquacycline ¨ vet. (50 mg/ml Hjeltnes, B., Bergh, O., Holm, J.C. and Wergeland, H., Oxytetracycline). Two groups were bath treated 1995. The possibility of transmission of furunculosis with Flumequine (0.5 g/l) for three hours, and from farmed salmon to marine fish. Diseases of AquaticOrganisms, 23: 25-31.
two groups kept as control. Dead and moribund Nylund, A. and Jacobsen, P., 1995. Sea trout as a carrier of infectious salmon anaemia virus. Journal of Fish At the termination of the experiment, 28 days after treatment, the cumulative mortality was 47.5 Nylund, A., Kvenseth, A.M., Kross¿y, B. and Hodneland, % both in control groups and Tribrissen injected K., 1997. Replication of the infectios salmon anaemiavirus (ISAV) in rainbow trout, Oncorhynchus mykiss (Walbaum). Journal of Fish Diseases, 20: 275-27 mortality reached 34% while in the Aquacyclin-treated groups mortality was only 14%.
Summary of the Irish sea trout problem
Salmon Research Agency, Co. Mayo, Ireland This article was circulated on the sealice e-mail discussion group in August 1998 In reply to those requests for information on the sea trout collapse in the west of Ireland and whether sea lice were the cause of the collapse, it was clear from the uninformed statements and ordinated a broadly based research programme questions that have appeared recently on e-mail which, it was hoped, would identify the extent of that it is necessary to restate the problem and the problem and define a possible cause or causes.
where it has occurred. There is a substantial body of published reports and papers which are implicating sea lice as the major component of the collapse, are summarised in Whelan (1992).
During the following two years the research species, there has been increasing evidence during programme concentrated on five principal areas: the past two decades of a slow decline in some • Monitoring of sea trout survival in a range of stocks and this was largely attributed to poaching with fine mesh monofilament and a range of • Further investigations into the role of sea lice environmental problems such as: field drainage,stream drainage and maintenance fertilization of • A physiological profile of sea trout smolts to the hillsides, afforestation and more recently study their state of fitness when entering hillside erosion, due to overgrazing by sheep Whelan (1991, 1992, 1993) and Poole et al.
• The development of practical sea trout (1996), described the appearance of a more serious decline which appeared in many fisheries In 1991 the Department of the Marine established along the western seaboard in 1986 which, by a Sea Trout Working Group and the results of the 1989, resulted in a population collapse in most sea trout research programme were examined by mid-western sea trout fisheries. Subsequent this group at the end of each year (Anon, 1991, research programmes (Anon 1990, 1992, 1993, 1992, 1993, 1994). The "sea trout problem" in 1994) confirmed that the declining rod catches the Irish context was defined as the following: reflected an actual spawning stock collapse,approximately 90-98% reduction in ova deposition rates in one catchment studied.
severe infestations of juvenile (chalimus)stages of lice, Lepeophtheirus salmonis.
The major collapse occurred in 1989 when, the presence of larger badly emaciated fish tragically, there was little sea trout research a severe reduction in spawning stock, across taking place and only some anecdotal information is available on the sequence of events which tookplace during the May/June period of 1989.
However, the following details are known: The most severe collapse in sea trout stock levels occurred in the area from Clew Bay in some mending kelts appeared in the estuaries the north to Galway Bay in the south.
Of the 60+ rivers sampled around the coast of Ireland between 1991 and 1996, no exception has been found to the observation that the sea available showing the level of lice damage trout problem, as defined above, has been to the skin and fins of the more seriously recorded only in areas where salmon farming In some fisheries, appreciable numbers of • No evidence of a disease was found which In the latter half of the 1980's, farm salmon was consistent with the stock collapse. A production in the bays of the mid-west of Ireland range of internal parasites were identified but expanded to an unprecedented extent. Sea lice none that provided an explanation for the consequence juvenile lice production soared. No Holland & Poole 1993; Anon. 1991).
observed data exist for juvenile lice production • There was no evidence of sea trout feeding during this period but extrapolation from the lice regularly in the vicinity of cages, where it was production figures indicates the massive release claimed pollack and coalfish were eating the of larvae which took place at this time. It has also fish, or that sea trout smolts were straying been shown that increasing sea temperatures in the late 1980's were directly linked with faster • From the stomachs of the sea fish caught, generation times in the louse life cycle (Tully & while sampling for sea trout, there was no evidence of reduced food availability at sea or a lack of specific food items (e.g. sandeels).
shown; the sea trout smolts, and adults where The collapse in the elver (young eel) stocks present, are consistently infested by juvenile lice and predation by seals were also discounted.
and that in the mid-west of Ireland during 1991, • While acid flushes or chronic acidification 95% of the total nauplius larval production of Lepeophtheirus salmonis, the louse causing the problem, was of fish farm origin. It has also been direct evidence to identify a causal link.
shown that sea trout were infested with juvenile lice within two to three weeks of migrating to sea environmental changes have taken place and and that morphological and physiological impact these undoubtedly affect stocks in specific of the lice on the trout was sufficient to cause catchments. The sea trout stock collapse, correlations have also been found between both individually or collectively to these changes.
abundance and intensity of lice on sea trout with • No global failure of osmoregulatory ability of distance from neighbouring fish farms. While sea trout, which could explain the premature these correlations are by their very nature return of sea trout smolts to rivers, was relatively crude, they have provided the impetus for further detailed in-bay research into themechanisms governing sea lice infestation from The only consistent factors to emerge from the research carried out to date are the early return of In 1996 the Salmon Research Agency attended both smolts and kelts to the estuaries in early to the ICES Working Group in Edinburgh and the main conclusions of this group were as follows: infestations of juvenile salmon lice (Anon. 1991, • Highest numbers of lice on wild sea trout 1993a, 1993b, 1994; Tully & Whelan 1993, Tully post-smolts in Ireland, Scotland and Norway et al. 1993a, Tully et al. 1993b). The sea trout comparable levels of infestation have not observed in areas adjacent to intensive salmon been recorded outside farming areas (also farming. The problem is therefore geographically note ref. Tingley et al. 1997, ICES J. Mar.
distinct and any valid hypothesis must be able to • The phenomenon of sea lice related early returning sea trout post-smolts and related promoted as having been involved but results to date, particularly the high survival rates of stocked parr, would indicate that it is a marine • In Norway, sea trout post-smolts do not return based mortality of trout and no common factor, or early except where they are infested with sea suite of factors, have been identified as having lice. These infestations are dominated by caused the sea trout stock collapses in the west of juvenile stages, as also observed in Scotland Ireland. The "building of dams, roads, gravel digging, silage etc" (Kvenseth, Caligus 20/7/98) do not have any connection with the current sea It is now known that salmon lice cause stress, trout situation in the west of Ireland.
mortality to host fish such as sea trout, salmon Poole, W.R., Whelan, K.F., Dillane, M.G., Cooke, D.J. and Matthews, M. 1996. The performance of sea trout, Salmo trutta l., stocks from the Burrishoole system western Ireland, 1970-1994. Fisheries Management & infestation on early returns of sea trout post- Poole, W.R. & Whelan, K.F. (1996). The sea trout stock in salmon lice significantly shorten sea trout's the Burrishoole catchment and a review of the symptoms of the west of Ireland sea trout collapse. Paper presented to: ICES Workshop on the Interactions between Salmon Data relating to the proximity of fish farms Lice and Salmonids, ICES CM 1997/M:4.
and the lice infestations in sea trout from Tully. O., 1991. Assessment of the impact of sea lice Scotland indicate that a similar correlation to (Lepeophtheirus salmonis) infestation on sea trout smolts Ireland may have been present in 1994 - the on the west coast of Ireland during 1990 and 1991. The only year considered in detail by the ICES Salmon Research Agency of Ireland Inc. Internal Report.
(unpubl.) 37pp.
Tully, O., Poole, W.R. and Whelan, K.F. 1993a. Infestation • The data suggest that lice emanating from fish parameters for Lepeophtheirus salmonis (Kroyer) farms may transfer to wild trout populations (Copepoda:Caligidae) parasitic on sea trout (Salmo trutta but this has as yet not been quantified.
L) post smolts on the west coast of Ireland during 1990 and 1991. Aquaculture and Fisheries Management, 24 Tully, O., Poole, W.R. and Whelan K.F. and Merigoux • The scarcity of wild salmonids inshore in 1993b. Parameters and possible causes of epizootics of Lepeophtheirus salmonis (Kroyer) parasitic on sea trout February to April reduces the possibility that (Salmo trutta L) on the west coast of Ireland.
Proceedings of the First European Crustacea Conference.
the spring pulse of larval lice was derived Paris, August 31 - September 5, 1992 Pathogens of wild from wild sea going salmonids present at or and Farmed Fish, Sea Lice (ed. by G.A. Boxshall). Ellis Tully, O. and Mulloy, S. 1993c. Infestation of sea trout The commisioned report examining the 1992 - (Salmo trutta L.) by the salmon louse (Lepeophtheirus 1996 sea trout sampling programme, undertaken salmonis (Kroyer) in Ireland during 1993. ICES CM by Dr Ian Cowx, identified a number of perceived and actual inaccuracies in the programme. These Tully, O., Gargan, P. and Whelan, K.F. 1993d. Infestation were fully addressed in the 1997 programme. The of sea trout (Salmo trutta L.) by sea lice (Lepeophtheirus inaccuracies identified were found to have not salmonis (Kroyer)) in systems close to and distant fromsalmon farms in Ireland. ICES CM 1993/M:56.
significantly altered either the database or the Tully, O. and Whelan, K.F. 1993e. Production of nauplii of conclusions drawn from it and the 1997 modified Lepeophtheirus salmonis Kroyer) (copepoda:caligdae) programme completely corroborated the 1992- from farmed and wild Atlantic salmon (Salmo salar L) on the west coast of Ireland during 1991 and its relation to Hopefully this description of the current status infestation levels on wild sea trout (Salmo trutta L).
Fisheries Research 17. 187-200.
Whelan, K.F. 1991. Disappearing sea trout - decline or population collapses in the west of Ireland will collapse? The Salmon Net No. 23. 24-31.
help to inform those looking for such information.
Whelan, K.F. 1992. Management of salmon and sea trout stocks. Environment and Development in Ireland.
Bibliography
Proceedings of a Conference held at University College Anon., 1990. Declining sea trout stocks in the Galway / Dublin. The Environmental Institute, University college south Mayo region - A scientific appraisal. The Salmon Research Agency of Ireland Inc. Internal Report.
Whelan, K.F. 1993. Historic overview of the sea trout collapse in the west of Ireland. In: Aquaculture in Anon., 1991-94. Reports of the Sea Trout Working Group.
Ireland - towards sustainability. Ed. J. Meldon.
Fisheries Research Centre, Department of the Marine, Proceedings of a Conference held at Furbo, Co. Galway.
30th April - 1 May. 1993. 51-53. An Taisce, Dublin.
Mulloy, S., Holland, C. and Poole, R. 1993. Helminth Whelan, K.F. 1993. Decline of sea trout in the west of parasites of brown and sea trout Salmo trutta L. from the Ireland: an indication of forthcoming marine problems west coast of Ireland. Biology and Environment: Proc.
for salmon? Proceedings of the Fourth International Roy. Ir. Acad., Vol. 93b no. 3. 137-142.
Atlantic Salmon Symposium, St. Andrews, N.B. Canada, Murphy, T., Drinnan, E.H., Poole, W.R. and Whelan, K.F.
June 1992. Salmon in the Sea and New Enhancement 1993. Histological and virological investigations into the Strategies - (Ed. D. Mills) Fishing News Books, Chapter collapse of sea trout populations in the west coast of Sea lice management methods in Scotland
Marine Harvest McConnell, Lochailort, Inverness-shire PH38 4LZ, U.K.
This paper was presented at the workshop on sea lice control on fish farms in Trondheim, November1997. Introduction
(a) sea lice infestation patterns on farms in Scotland investigating whether the source of infection isexternal or is generated from within the farms; (b) factors governing infestation cycles and the pattern of infection; (c) methods to prevent and treat sea lice and (d) the choice of medicine, the timing of the treatment and how frequently the fish should be treated.
Internal or external infection patterns?
sites and it is difficult to conclude whetherCaligus are an increasing problem. Annual Smolts (1992 year class) stocked on a production fluctuations in settlement of Caligus on salmon farm in west Scotland with one sea winter were evident on a farm in Loch Sunart over four production fish already present (1991 year class) year classes (Fig 2). Treatment with Aquagard- were rapidly infected with Lepeophtheirus Novartis (dichlorvos 50% w/v) is normally very salmonis and copepodids were found on the effective in removing Caligus, and there is no newly stocked fish within 3 days (Fig. 1). Up to 8 indication of reduced sensitivity to this mobile L. salmonis were recorded 4 weeks after stocking and the fish were treated with Aquagard(dichlorvos) at regular intervals through the first In farms that have been fallowed the recruitment summer. In the following year the farm was of lice in late spring in the second year is a fallowed for several weeks and this subsequent critical period in sea lice control (Fig. 3). In this year class remained relatively uninfested with lice example there was an initial infestation with through the first year and only one treatment with Caligus and this declined naturally without Aquagard was required during this period. In many farms where fallowing is applied, lice numbers of chalimi of L. salmonis increased treatment is not required for up to 15 months rapidly followed by a rise in weeks 18 to 20 of following transfer to sea and this treatment can be mobile L. salmonis to an average of 12 per fish.
then solely for Caligus elongatus rather than L. At this point fish were treated with Aquagard.
salmonis. This was also the conclusion from an One further treatment was required at the intensive study of four Scottish salmon farms that beginning of August. The increase in lice established that recruitment of lice was initially slow following fallowing and emanated from logarithmic. Several factors may be involved in wild fish (Bron et al., 1993). Thereafter the build this rapid increase in sea lice infestation in weeks up of lice was largely internally generated within 16-20, including increasing day length, rising water temperatures and increasing salinity(allowing greater larval survival). In addition, The pattern of infestation with Caligus follows a copepodids may be less viable in winter due to well established direct route of transfer from wild smaller egg size and a reduced nutrient reserve, although larger numbers of smaller eggs are therefore fallowing has little effect on controlling produced. In late spring fewer larger eggs are this species. Caligus numbers on salmon often produced, and larger eggs may give more viable decline naturally with the onset of colder weather in November or an influx of freshwater. Therecruitment of Caligus varies greatly between Estuarine plankton are adapted to prevent wash been used to give protection in cages. On one out including mechanisms for vertical movement farm used as an example (Fig. 5) smolts were in seawater. Nauplii and copepodids of sea lice stocked with larger fish, as this was a broodstock are likely to behave in the same way as other site. In 1994 smolts were treated with Aquagard zooplankton. Bron et al. (1993) indicated the on three occasions but no treatment was required average survival time of copepodids at 10°C as 7 in 1995 after wrasse were stocked on a group of 8 days but it could be as much as 21 days in a farm situation in a confined bay area. Two tides each Wrasse have been found to be less effective in day, each with flow and ebb movements, provides the second year of the production cycle. I have four opportunities per day for copepodids to pass carried out a trials with larger corkwing wrasse through a farm. Over a week this is 28 occasions, on 2 cages but with little effect. An alternative and over 3 weeks 84 opportunities. Together with would be to try ballan wrasse as good results high egg production this can explain the rapid using ballan have been reported from Norway.
increase in lice numbers from a relatively small Ballan are relatively uncommon in Scotland (Treasurer, 1996b), about 1% of the catch, and Lice control methods in Scotland
culture of ballan would be required.
Part of the ineffectiveness of wrasse in the management is being followed and this may second year is the disappearance of wrasse over the first winter. Special hides have been companies in certain sea loch areas.
developed by Martin Sayer of the DunstaffnageMarine laboratory, Oban providing a buffer to sudden changes in salinity and temperature.
These have been trialled on farms but with no companies operating in Loch Sunart included conclusive results; although survival of wrasse specifying a fallow period, on stocking a single improved, they continued to be lost from the year class, and on exchanging information on the cages. Wrasse were not found dead and therefore health of the fish. Prior to this, in the 1989 year it was assumed that they have escaped through class, lice infested fish rapidly following stocking and remained high through the production cycle Another problem has been the occurrence of an (Fig. 4). The first treatment with Aquagard was in atypical furunculosis, Aeromonas salmonicida, in September of the first year and a total of 22 wrasse following capture, transfer and stocking in treatments was required in this year class. In 1991 cages. Wrasse should be vaccinated although the when a fallow period of 8 weeks was used, induction period is too short and there would numbers of L. salmonis were low through the first year with only Caligus present in any numbers and not sufficiently high to require treatment. Itwas 15 months before the first treatment was required. Fallowing was therefore very effective There are only three licensed medicines for with a 50% reduction in the number of treatments treatment of salmon infested with sea lice in compared with the 1991 year class. The option to Scotland. Dichlorvos (Aquagard-Novartis) as 1 fallow may not be available to small companies ppm active is applied as a bath treatment with the who have a limited number of farms or only one cage enclosed with a tarpaulin. The discharge of farm and where fish of various sizes are required this medicine is regulated by the Scottish Environmental Protection Agency and the volume of dichlorvos that can be discharged has beenreduced in many cases in line with the Paris In 1994 a questionnaire was sent to fish farming Convention 1974 for the protection of the North companies in Scotland asking about their use of wrasse (Treasurer, 1996a). Wrasse were stocked requirement to reduce the use of various toxic widely with the smolt input, 150,000 wrasse in and persistent chemicals including dichlorvos.
1994 representing 33% of farms and 39% of fish put to sea that year. Wrasse have been effective available to treat a farm once per annum. Also in the first year of the production cycle where many lice populations are resistant to the use of wrasse have been treated carefully and hides have LEGEND FOR FIGURESFig. 1. Comparison of numbers of mobile L. salmonis in 1991 on a farm in west Scotland with mixed yearclasses with 1992 after fallowing (single year class). Arrows indicate dates of treatment in 1991. Time is shownas the weeks of the year (i.e. 1-52 from January to December).
Fig. 2. Mean numbers of mobile Caligus elongatus in the first year of the production cycle in 1991, 1993, 1995and 1997Fig. 3. A typical pattern of infestation with L. salmonis showing the increase in lice numbers in the second year.
The reduction in numbers corresponds to 2 treatments with Aquagard.
Fig. 4. Comparison of numbers of mobile L. salmonis in 1989 when there was no management agreement with1991 when the sea loch system was fallowed.
Fig. 5. Comparison of numbers of L. salmonis in 1995 when wrasse were stocked with 1994.
Fig. 6. An example of the efficacy of hydrogen peroxide as a treatment for sea lice in spring of the second year ofthe production cycle. Arrows indicate treatment dates.
Fig. 7. A comparison of chalimus numbers in 1996 on a farm in west Scotland following 3 winter treatments(treatment dates indicated with an arrow) with 1994 when this policy was not applied.
Fig. 8. A comparison of numbers of mobile L. salmonis following winter treatments (compare Fig. 7).
this organophosphate, particularly at lower water medicine has to have a marketing authorisation in temperatures, and treatments can be ineffective (Jones et al. 1992). Azamethiphos (Salmosan, authorisation are submitted to the Veterinary Novartis) has recently been granted a marketing Medicines Directorate (VMD) and are assessed authorisation and discharge consents have been on the quality, efficacy and safety of the product.
The VMD is advised by the independentVeterinary Products Committee. Obtaining a The third medicine is hydrogen peroxide, supplied as Paramove by Solvay Interox and consuming and expensive process, e.g.
Salartect by Brenntag. This is also applied as a azamethiphos took 6 years from the beginning of bath treatment and can be very effective (Fig. 6).
the Animal Test Certificate (ATC) trials.
Although up to 80% of lice recovered fromtreated cages were active after an hour (Treasurer Un-licensed medicines can be prescribed by a & Grant, 1997), there have been no reported veterinarian where treatment is necessary on cases of significant resettlement on salmon. The main problem with hydrogen peroxide is toxicity alternatives are considered as being ineffective.
at water temperatures in excess of 14°C. In The veterinarian makes a series of decisions addition, chalimi are unaffected, effectiveness against mobile lice may not be complete, and egg In addition, the medicine has to be granted a bearing females are more difficult to remove.
discharge consent by the Scottish Environmental These medicines are both applied as a bath Protection Agency (SEPA). Under section 23 of treatment and there can be variations in enclosed the Water Act 1989 fish farms are classified as volume compared with target volume. When the trade premises and any wastes are classified as tarpaulin has not been filled adequately a higher trade effluent and require a discharge consent.
more toxic concentration is achieved and with a An application for a consent has to made for each large fill the target concentration is not attained, individual farm and depending on the size of the farm extensive hydrographic data are required to applications are labour intensive, may stress fish, predict the scale of discharge that can be made and licensed medicines do not kill the larval without breaching short term Environmental stages. Furthermore, the appetite of fish is Quality Standards. An application for a discharge frequently affected by treatment and fish are consent is advertised in the local press.
starved on the day before and during treatment.
Following extensive laboratory and field trialsand environmental impact studies, SEPA gave alimited issue of restrictive consents for Alternative treatments
ivermectin for a trial period. Efficacy has been Within the terms of the Medicines Act 1968, any good but there have been political issues in substance intended to be used as a veterinary national strategy was launched by the Scottish Pharmaceuticals) has been trialled under an Animal Test Certificate and this medicine will planned sealice treatments throughout designated shortly receive a marketing authorisation. The areas in spring to coincide with the time of year product is very effective against mobile and to a when copepodid survival has been shown to be lesser extent larval stages. Discharge consents lowest (Wadsworth et al., 1998). The results of the strategy have not been published but havebeen reported to be favourable and further No in-feed treatment is licensed (but see improvement will be possible if more effective ivermectin), although three possibilities have medicines such as cypermethrin are more widely been used in limited trials under ATC. Onions and garlic have been tried in bags and in feed butwere ineffective. Neither have light luresdemonstrated efficacy.
References
The development of a successful vaccine is notimminent. While immune stimulants have given Bron, J. E., Sommerville, C., Wootten, R. & Rae, G.
good laboratory results (Simon Wadsworth, pers.
(1993). Fallowing of marine Atlantic salmon, comm.), they have not been found to be effective Salmo salar L. farms as a method for the control of sea lice, Lepeophtheirus salmonis (Kroyer, 1837).
Journal of Fish Diseases 16, 487-493.
Immediate assistance would be the provision ofother more effective medicines but at present the Jones, M.W., Sommerville, C. & Wootten, R. (1992).
most effective use of current medicines must be Reduced sensitivity of the salmon louse, considered, particularly hydrogen peroxide. This Lepeophtheirus salmonis to the organophosphate involves strategic or winter treatments; treating dichlorvos. Journal of Fish Diseases 15, 197-202.
fish when sea lice numbers are low and stable at Ritchie, G., Mordue, A.J., Pike, A.W. & Rae, G.H.
the beginning of the year. Ritchie et al. (1993) (1993). The reproductive output of Lepeophtheirus showed that many small eggs are produced at this salmonis adult females in relation to seasonal time and survival of copepodids is poor because variability of temperature and photoperiod. In : of a low nutrient reserve. In an example from Pathogens of wild and farmed fish: sea lice.
Boxshall, G.A. & Defaye, D. Ellis Horwood, Loch Sunart fish were treated with hydrogen peroxide on 3 occasions from March atapproximately 6 weekly intervals, weeks 10, 17 Treasurer, J.W. (1996a). Wrasse (Labridae) as cleaner- and 23 (Fig. 7). This had the effect of reducing fish of sea lice on farmed Atlantic salmon in west the spring increase in sea lice numbers. A Scotland. In: Wrasse: biology and use inaquaculture. Sayer, M.D.J., Treasurer, J.W. & comparison is made of the 1993 with the 1995 Costello, M.J. Fishing News Books, Oxford, 185- year class in the second year of the production cycle. Chalimus numbers in 1996 weresignificantly less (ANOVA on log transformed Treasurer, J.W. (1996b). Capture techniques for data, P<0.05), 5.5 on average compared with 21.8 wrasse in inshore waters of west Scotland. In:Wrasse: biology and use in aquaculture. Sayer, in 1994 (Fig. 7). Numbers of mobile L. salmonis M.D.J., Treasurer, J.W. & Costello, M.J. Fishing were also less, 13.4 weekly average for the second year compared with 31.1 in 1994 (Fig 8).
The number of treatments in the second year was Treasurer, J.W. & Grant, A. (1997). The efficacy of reduced by up to 46%, the length of time between hydrogen peroxide for the treatment of farmedAtlantic salmon, Salmo salar L. infested with sea treatments was extended, damage to fish was lice (Copepoda: Caligidae). Aquaculture 148, 265- reduced, there were fewer mortalities and improved fish quality (Wadsworth et al., 1998).
Wadsworth, S., Grant, A. & Treasurer, J.W. (1998). A This policy and procedure should be allied to strategic approach to lice control. Fish Farmer 21 coordinating treatments between farms in a prescribed area and followed up with subsequenttreatments based on a lice surveillance system.
The availability of more effective medicines willenhance the success of this initiative. Recently a Vaccine against salmon lice
Dr Rob Raynard
FRS, Marine Laboratory, Victoria Road, PO Box 101, Aberdeen AB11 9DB, Scotland, U.K.
Summary of a project funded under the EC FAIR Research programme: AIR2-CT93-1079 The immune system of fish, as in human, reacts against invading foreign substances. Faced with adisease, the immune system will try to eliminate the infectious agent or substance, for example infectiousbacteria, as soon as it has been identified. However, the infection may be too advanced by the time theimmune system is fully reacting. Vaccines can accelerate this process. During vaccination, specificportions of the infectious agent (antigens) are injected to stimulate a specific reaction of the immunesystem (build up of antibodies) to prevent recurrence of the disease. The risk of infection is limited, asonly antigens and not the disease agent are injected. During future infections, the immune system willreact quicker to the already known disease and consequently improve the chances of survival of theanimal.
This common method of vaccination can not be developed against lice as only the exoskeleton and mouthparts of the lice are in contact with the fish. The immune system does not recognise any foreignsubstances in the blood stream and the active defence mechanisms are not being triggered. However, licefeed on skin and mucus of salmon and thereby take blood meals. As the antibody, which recognise thetarget, and the white cells, which destroy it, are present in the blood, it was suggested that fish mightfight against lice externally through the action of their blood’s defence mechanisms ingested by the lice.
Indeed, if the immune system is prepared to react against gut cells of lice, it will be triggered within thelice gut and against it. Therefore, lice could be eradicated by the action of the fish immune systemfollowing a blood meal. Such vaccination techniques have been used to fight bloodsucker parasites ofcows and sheep.
The partners of this project managed to design several vaccines aimed to be used as described above.
However, tests on salmon challenged with lice showed only a limited efficacy of the vaccination. Severalreasons may explain this poor success. Firstly, lice, unlike bloodsuckers, only ingest a limited amount ofblood. Secondly, there is still room for some improvements of the vaccine. Nevertheless, this newapproach for treatment of parasites in fish is of great interest and research efforts are being continued toimprove the present vaccine. Further development may be expected in a near future.
Cloning and characterisation of Lepeophtheirus salmonis microsatellite genetic elements as useful
tools for the study of sea lice ecology.
Brief description of project
A two-year research project funded under the Operational Programme for Fisheries (1994-1999) andadministered by the Marine Institute (Dublin) seeks to develop DNA profiling techniques and examinetheir usefulness in improving our knowledge of the ecology of the sea louse Lepeophtheirus salmonis.
The method being developed is based on examining repetitive DNA elements termed microsatellites, andis used in conjunction with the polymerase chain reaction (PCR) allowing the genetic profile ofindividual sea-lice to be determined. This type of DNA fingerprinting has proved useful in the researchof other species including areas such as identity testing, pedigree analysis, disease diagnosis, andpopulation genetics. Once described, the DNA profiling tools will be tested and assessed for theirability to detect genetic variation in sea-lice recovered from both farmed and wild fish. The researchaim is to describe the genetic variation within identified single populations of L. salmonis and alsobetween different populations of L. salmonis.
The work is being conducted by Dr Richard Powell (Department of Microbiology) and Dr Sam Martin,(National Diagnostics Centre, BioResearch Ireland) of the National University of Ireland, Galway. Theyare currently at the half-way mark, and have cloned and determined the DNA sequence of forty sea-licemicrosatellites, and developed ten microsatellite-PCR assays. The final year of the project will now bespent examining whether these new DNA profiling tests have the potential to provide new informationon the monitoring and movement of sea-lice populations.
Semiochemicals for sea lice control
Zoology Department, Aberdeen University, Tillydrone Avenue, Aberdeen AB24 2TZ.
Semiochemicals are naturally occurring chemicals As a result of these studies, we now have unequivocal evidence that male and female salmon organisms. Some of these compounds have been lice exhibit behavioural responses to a variety of exploited in order to regulate insect behaviour. For fish-derived stimuli, and that the molecules example, sex pheromones are used to lure, trap involved are quite stable in seawater. These and disrupt the behaviour of some moth pests1 and responses are directional and kinetic, and provide the compounds that attract some veterinary pests the first evidence that L. salmonis exhibits a to their mammalian hosts have also been used in positive rheotaxis to fish-conditioned water.
traps2. Such approaches now form important semiochemical sources elicit the greatest attractant response, we will extract the organic components The theory, methodologies and technologies that have given rise to such strategies are now electrophysiological techniques to record the being applied to the problem of Lepeophtheirus sensory responses of lice to these compounds. The salmonis. We are in the process of identifying the aim of this is to show a clear relationship between semiochemicals which attract salmon lice to their hosts and male lice to their mates*. It has long chemoreceptors and the triggering of host-finding been suggested that parasitic copepods use fish- behaviour. At this point we can embark on derived odours, at least in part, to identify their detailed studies of the particular molecules hosts3,4 and preliminary work has shown that lice eliciting this chain of events. It is these we hope to do have a behavioural response to these stimuli5.
investigate for their potential in trapping and The successful identification of such compounds will allow us to investigate the possibilities ofdesigning lice traps or of creating disruptive *Link Aquaculture (SAL 11). Aberdeen University - AJ Mordue, AW Pike, W Mordue; Nottingham University - I Currently, our research focuses on host-finding Duce; IACR-Rothamsted - JA Pickett, L Wadhams. Fundedby Natural Environment Research Council, the Scottish behaviour by adult lice. Significant numbers of Salmon Growers Association and the Shetland Salmon lice transfer between hosts in sea cages, and host- Farmers Association. In collaboration with Marine-Harvest finding may be important in the reattachment of lice dislodged from their hosts, and for the (1) Howse P, Stevens I, Jones O (1996) Insect Pheromones redistribution of males searching for unmated and Their Use in Pest Management. Chapman and Hall,London 256pp.
females6. It may also prove possible to encourage (2) Torr SJ, Mangwiro TC (1996) Upwind flight of tsetse lice to leave their host given sufficiently strong (Glossina spp) in response to natural and synthetic host odour in the field. Physiological Entomology 21 (2) 143-150.
In this initial phase, the project centres on the (3) Fasten N (1913) The behaviour of a parasitic copepod design and use of simple flow chambers allowing Lernaepoda edwardsii Olsson. J Anim Behav 3 36-60.
different stimuli, present in host–conditioned (4) Boxshall GA (1976) The host specificity of seawater, to be proffered to lice. The copepods are Lepeophtheirus pectoralis (Muller1776)(Copepoda:Caligidae). J Nat. Hist 8 681-700.
(5) Hull MQ (1997) The Role of Semiochemicals in the behavioural responses. Using a digital tracking Behaviour and Biology of Lepeophtheirus salmonis (Kroyer system, the relative strength of these responses can 1837): Potential for Control? PhD Thesis. University of be assessed by measuring the speed and direction of movement. Other assays, which allow the lice (6) Hull MQ, AJ Mordue, AW Pike, G Rae (1998) Patterns of to exhibit preference for one stimulus over pair formation and mating in an ectoparasitic caligid copepodLepeophtheirus salmonis (Kroyer 1837); implications for its another, are used to gauge whether a stimulus is an sensory and mating biology. Phil.Trans.R.Soc.Lond.B. 353 attractant. By making a choice of odours available to the lice, we can discern which are the moreeffective.
Aqua TT – European Aquaculture Network
Aqua TT is a European Network of co-operative Universities and Industries involved in the aquaculturesector with the following main aim: "To support the strategic goals of the aquaculture industry by facilitating collaborative university/industry action in education, training, technology transfer, research and development." Aqua TT was founded in 1992 under the EU COMETT programme as the University Enterprise TrainingPartnership (UETP) for the European aquaculture industry. The initial proposal arose from theidentification of a clear need to systematize, coordinate and develop the training requirements of theindustry through a single body.
AQUAFLOW- European Network for the
dissemination of Aquaculture RTD information
participation in a number of EUprogrammes such as COMETT,LINGUA, FORCE, TEMPUS, FAIR, The European Aquaculture Society (EAS), Aqua TT and the Federation of European Aquaculture Producers (FEAP) are jointly promoting a new EU • Transnational exchanges of staff from Known as AQUAFLOW, the project aims to establish a wider and more rapid circulation of information concerning the results and progress of EU funded(and, eventually, relevant non-EU funded) programmes for research, technological development and demonstration (RTD) in aquaculture. The target is the potential end user in Europe and will include farmers, technicians, vets and other professionalpeople who are active within the aquaculture sector.
The project works in a simple manner- each month a number of single-page sheets will be prepared. Thesetechnical sheets will provide a concise summary of the research project, together with the main findings and conclusions. The sheets will then be widely distributed, reaching aquaculture interests across Europe. In addition a series of workshops are planned over the 3 year period, the first being scheduled for"Aquaculture Europe" to be held in Bordeaux, France network of almost 600 membersthroughout the European aquaculture Aquaflow will also collect feedback from the small and medium aquaculture enterprises (SMEs) to be able to identify further the needs for aquaculture research institutes, governmental laboratories and & technology and associate information services as well as being able to respond to problems and bottlenecks encountered in the project.
for the European aquaculture sector.
Further information on the project available from: Frederic Luizi, EAS Secretariat, Slijkensesteenweg 4, 8400 Oostende, Belgium Tel: +32 59 32 38 59 Fax: Report on the 1998 sealice conference in Amsterdam
About 70 persons attended the sealice sessions at the Fourth International Crustacean Congress, July 20-24,Amsterdam. Delegates were from industry (43%) universities (41%), government (14%) and non-governmental(2%) organisations. Many of these papers have been submitted for publication and are currently undergoing peerreview. The proceedings will be published in the journal Contributions to Zoology (formerly Bijdragen tot deDierkunde). The following papers were presented at the sealice workshop sessions. Note that the titles andauthorships of papers submitted for publication in the proceedings do not necessarily match those presented at theconference.
Banks, B.A., A.P. Shinn, J.E. Bron & C. Sommerville. The having implications for inter-host transfer of use of RAPDs to establish the interspecific relationships of the ectoparasitic caligid, Lepeophtheirus salmonis (Krøyer, Ibrahim, A., B.M. MacKinnon & M.D.B. Burt. The influence of sub-lethal levels of zinc on smoltifying Bashirullah, A.K. Non-interactive coexistence of two Atlantic salmon Salmo salar L. and on their subsequent parasitic copepods of Caranx hippos in eastern Venezuela.
susceptibility to infection with Lepeophtheirus salmonis Bell, S., J.E. Bron, & C. Sommerville. The distribution of exocrine glands in Lepeophtheirus salmonis (Krøyer, 1837) Jackson, D., S. Deady, D. Hassett & Y. Leahy. Population and Caligus elongatus Nordmann, 1832.
dynamics of sea lice on wild sea trout post smoults.
Boxaspen, K. & T. Næss. Development of eggs and Jackson, D., S. Deady, D. Hassett & Y. Leahy. Caligus planktonic early life stages of salmon lice (Lepeophtheirus elongatus Nordmann as parasites of farmed salmon in salmonis) at low temperatures.
Braidwood, J.C. The use of Crangon Crangon to investigate Jackson, D., D. Hassett, S. Deady & Y. Leahy.
the potential environmental impact of Excis sea lice Lepeophtheirus salmonis (Krøyer) (Copepoda: Caligidae) Bron, J.E., A.P. Shinn & C. Sommerville. Ultrastructure of McAndrew, K., R. Wootten & C. Sommerville. Survival and the cuticle of the chalimus larva of the salmon louse egg production of Lepeophtheirus salmonis in experimental Lepeophtheirus salmonis (Krøyer, 1837) (Copepoda: infections of Atlantic salmon (Salmo salar).
Nordhagen, J.R., P.A. Heuch & T.A. Schram. Size as Bron, J.E., A.P. Shinn & C. Sommerville. A description of indicator of origin of salmon lice Lepeophtheirus salmonis moulting in the chalimus larva of the salmon louse Lepeophtheirus salmonis (Krøyer, 1837) (Copepoda: Roth, M. The availability and use of chemotherapeutic sea Bron, J.E., G. Wainwright, R.P. Smullen & C. Sommerville.
Schram, T.A. The egg string attachment mechanism in The cuticle and ecdysis in larval stages of Lepeophtheirus Lepeophtheirus salmonis (Copepoda: salmonis (Krøyer, 1837) (Copepoda: Caligidae).
Costello, M.J. & A.W. Pike. Towards a quantification of Shinn, A.P., B.A. Banks, N. Tange, J.E. Bron, C.
salmon lice population dynamics and infestation potential.
Sommerville, T. Aoki & R. Wootten. Comparison of 18S Dawson, L.J., A.W. Pike, D.F. Houlihan & A.H. McVicar.
and 1TS sequences obtained from Lepeophtheirus salmonis Effects of Sea Lice, Lepeophtheirus salmonis, on Sea parasitising Atlantic salmon (Salmo salar) in Scotland.
Trout, Salmo trutta, at different times after seawater Shinn, A.P., Bron, J.E., Gray, D.J. & C. Sommerville.
Elemental analysis of Scottish populations of the El-Rashidy, H. & G.A. Boxshall. Coevolution of the ectoparasitic copepod Lepeophtheirus salmonis (Krøyer, parasitic copepods of the family Ergasilidae (Poecilostomatoida) and host fishes of the family Treasurer, J.W., A. Grant & P.J. Davies. Physical constraints of bath treatments of Atlantic salmon (Salmo salar) infested Firth, K.J., S.C. Johnson & N.W. Ross. Investigation on the with sea lice (Copepoda: Caligidae).
role of skin mucus proteases of Atlantic salmon during Tully, O., W.R. Poole, K.F. Whelan. Temporal variability in Lepeophtheirus salmonis infestation.
physiological conditions of sea Trout in the marine Grimnes, A., B. Finstad & P.J. Jacobsen. Salmon lice: environment: Implications for the impact of Sea Lice on Haji Hamin, H.L., J.E. Bron, A.P. Shinn & C. Sommerville.
Tully, O., P. Gargan, W.R. Poole, K.F. Whelan. Spatial and The occurrence of blood feeding in Lepeophtheirus temporal variation in Sea Lice infestation of Sea Trout in Hull, M.Q., A.W. Pike, A.J. Mordue & G.H. Rae. Should I Vikeså, V. & K. Boxaspen. The effects of salinity and stay or should I go? New on- and off- host parasite data temperature on early life stages of salmon lice,Lepeophtheirus salmonis.
Recent publications on sealice
Collier, L. M. and Pinn, E. H. 1998. An assessment of the and field studies of effects of dichlorvos exposure on acute impact of the sea lice treatment ivermectin on a acetylcholinesterase activity in the gills of the mussels, benthic community. Journal of Experimental Marine Mytilus edulis L. Aquatic Toxicology 38, 125-143.
Biology and Ecology, 230(1), 131-147.
McVicar, A. H. 1997. Disease and parasite implications of Costelloe, M., Costelloe, J., Coghlan, N., O'Donohoe, G.
the coexistence of wild and cultured Atlantic salmon and O'Connor, B. 1998. Distribution of the larval populations. ICES Journal of Marine Science, stages of Lepeophtheirus salmonis in three bays on the west coast of Ireland. ICES Journal of Marine Science Murison, D. J., Moore, D. C., McHenery, J. G., Robertson, N. A. and Davies, I. M. 1997. Epiphytic invertebrate Davies, I. M, Gillibrand, P. A., McHenery, J. G. and Rae, assemblages and dichlorvos usage at salmon farms.
G. H. 1998. Environmental risk of ivermectin to sediment-dwelling organisms. Aquaculture, 163, 29-46.
Thain, J E, Davies I M and G H Rae, 1997. Acute toxicity Dawson, L. H. J. 1998. The physiological effects of of ivermectin to the lugworm, Arenicola marina.
salmon lice (Lepeophtheirus salmonis) infections on returning post-smolt sea trout (Salmo trutta L.) inwestern Ireland. ICES Journal of Marine Science 55(2)193-200.
Grant, A. and Briggs, A. D. 1998. Toxicity of ivermectin Events Calendar
to estuarine and marine invertebrates. Marine PollutionBulletin, 36, 540-541.
Grant, A. and Briggs, A. D. 1998. Use of ivermectin in Aquaculture America ’99.
marine fish farms: some concerns. Marine Pollution Hull, M. Q., Pike, A. W., Mordue, A. J. and Rae, G. H.
1998. Patterns of pair formation and mating in anectoparasitic caligid copepod Lepeophtheirus salmonis(Kroyer 1837): implications for its sensory and mating Fifth Central American Symposium on
biology. Philosophical Transactions of the Royal Aquaculture.
Society of London B 353, 753-764.
MacKenzie, K., Longshaw, M., Begg, G. S. and McVicar, A. H. 1998. Sea lice (Copepoda: Caligidae) on wild sea trout (Salmo trutta L.) in Scotland. ICES Journalof Marine Science 55(2) 151-162.
World Aquaculture ’99
MacKinnon, B. M. 1998. Host factors important in sea lice infections. ICES Journal of Marine Science 55(2) 188- Exposition of the World Aquaculture Society.
Mo, T. A. and Heuch, P. A. 1998. Occurrence of Sydney, Australia, 26 April - 2 May 1999.
Lepeophtheirus salmonis (Copepoda: Caligidae) on sea trout (Salmo trutta) in the inner Oslo Fjord, south- http://ag.ansc.purdue.edu/aquanic/was/was.html eastern Norway. ICES Journal of Marine Science55(2) 176-180.
7th International Conference On Copepoda,
O'Donoghue, G., Costelloe, M. and Costelloe J. 1998.
Development of a management strategy for the Curitiba, Brazil, from 25 to 31 July 1999 reduction/elimination of sea lice larvae, Lepeophtheirus salmonis, parasites of farmed salmon and trout. Marine Resources Series No. 6, 51 pp.
Rolland, J. B. and Nylund, A. 1998. Infectiousness of organic materials originating in ISA-infected fish and 4th International Conference on SeaLice
transmission via salmon lice (Lepeophtheirus salmonis). Bulletin of the European Association ofFish Pathologists, 18(5), 173-180.
Schram, T. A., Knutsen, J. A., Heuch, P. A. and Mo, T. A.
Website: www.ecoserve.ie/projects/sealice 1998. Seasonal occurrence of Lepeophtheirus salmonisand Caligus elongatus (Copepoda: Caligidae) on sea 17th International Conference of the World
trout (Salmo trutta), off southern Norway. ICES Association for the Advancement of
Journal of Marine Science 55(2) 163-175.
Veterinary Parasitology, Copenhagen, 5-19
Davies, I. M., McHenery, J. G. and Rae, G. H. 1997.
Environmental risk of dissolved ivermectin to marineorganisms. Aquaculture 158, 263-275.
McHenery, J. G., Linley-Adams, G. E., Moore, D. C., Rodger, G. K. and Davies, I. M. 1997. Experimental Best current strategies for the control of lice on salmon farms
This document arose from the discussions at the Trondheim workshop on sea lice control on fish farms,as part of the EU Concerted Action on ”Lice control in Fish Farms”, under the FAIR programme, andwas drafted by Kjell Maroni, KPMG Management Consulting, Flatanger, Norway The following report is made as a pointed list, to avoid maturing females (keep the numbers and not as an in depth advice. This is done as a below 1 per fish, preferably zero!).
consequence of the fast development of new • A winter treatment (November - February), methods for lice treatment, and also is the most region, has given very promising results (see article by Treasurer in this issue).
• It is important to document past experience at Prevention of infestation
a farm so as future staff can consider this inplanning further treatments.
• Use single generations sites, or if not possible, fallow at least one month betweengenerations.
Treatment
• Avoid sites found to have persistently high biological method, using cleaner-fish (wrasse).
• Use cleaner-fish (wrasse) if possible.
The advantage is that they clean the fishcontinuously, and pick off the lice with egg These precautionary methods will also reduce the strings first. The disadvantage is their low transfer of other diseases within and between activity at low temperatures (< 6 °C), and the method is only partly developed for big salmon (>2 kg). However, Ballan wrasse seem very Monitoring
promising on such big fish (see Kvenseth article, Caligus, Issue 2). It is necessary to avoid heavily fouled nets, because the wrasse will feed on the when to treat if you don’t monitor lice.
fouling rather than the lice. It is also possible to • Motivation for lice sampling is important - capture lice released when moving or grading teaching about lice and “standard protocol for Chemical treatment can be used if preventive • Use monitoring results to get information methods or cleaner-fish do not do the job. The about the population structure and infection application of chemotherapeutants by spray or dip when grading is effective and uses and releases less chemicals. It was agreed that in-feed Exchange counting results between farms in methods seem very promising, but documentation and practical results are still scarce. For example the time between dose and effect on lice and • The initiatives of EwosAS and Skretting relative impacts on chalimus, mobile and egg (Nutreco) in distributing laminated A4 colour Chemical methods should be chosen so that the life cycle of the lice is broken. Bath methodseffective against juveniles should be chosen whentreating early in the life of the salmon, while Action level
methods killing the adult lice only can be used • The action level will depend on time of year.
Low numbers must be attained especially in • Short term methods: Chemical treatment the spring. The most important goal must be • Long term methods: Cleaner-fish (wrasse) and the consumer. However there is inadequate co-ordination between different regulations forchemotherapeutants both within and between Authorities
countries, including the EU and EEA countries.
It is important to have cooperation between the fish farmers and the authorities. The authorities permitted to be released into the sea or may not should go for a preventive strategy, and help the have maximum residue limits established for salmon farming industry to quantify benefits from lice control (economic, less lice pressure on wildfish, market image).
Future Research
It is felt that some countries (apart from Norway)have an over-protective strategy when it comes to Farmers need to have the methods and best legislation of new treatment methods. This can advice on how to treat lice now. The priority for result in resistance problems, and also leaves the action here is to improve management and co- farmers fewer methods to use under different ordination of regulations. A longer term view conditions. The authorities must use their “law- identified novel areas of research which may power” to force fish farmers who do not follow produce more effective treatments. This includes the agreed (co-ordinated) treatments in a region.
research into how lice find their host, if it is Both “carrot” and “stick” are necessary! possible to upset the digestive system of lice (e.g.
through a vaccine), and to improve techniques forthe use of different species of cleaner-fish to Regulations
control lice. Another priority is for moresophisticated and quantitative models of lice Most chemotherapeutants used against lice have population dynamics including their host location been developed for other animals so considerable behaviour and hydrographic conditions.
information already exists on their risk to staff New delousing compound, ALPHA MAX Tmvet, from ALPHARMA successfully in use in
Pelle Kvenseth reports the following news on a new lice control compound, from talking toAlpharma, fish vets and farmers. ALPHARMA has under general exemption from licensing, been given permission to sell a newlydeveloped delousing compound in Norway. ALPHARMA has been working with the developmentand testing of this new formula for the last four years. The new compound is a pyrethroid and is soldunder the trade name ALPHA MAX TMvet. As with all other treatment on farmed fish in Norway,both treatment and medicine must be prescribed by a veterinarian. Before permission is given by theNorwegian Medicine Control Authorities (SLK), corresponding to VMD in Great Britain, for a newdelousing compound, it has to be extensively tested. Many tests are necessary to establishconcentrations, effect on treated fish, effect on different life-stages of lice and effect on non targetorganisms and effect on the environment.
The active ingredient in ALPHA MAX is deltamethrin. The method of treatment is the traditionaluse of closed tarpaulin to surround the infected fish in a ‘bath’. Treatment concentration is 3 ppbduring 30 minutes in closed tarpaulin. The withdrawal period before slaughtering is 3 days. Thetreatment is reported to be effective against all stages of sealice, both sessile and mobile, and hasbecome very popular, especially in Western Norway and Trøndelag. According to veterinarians andfarmers, ALPHA MAX is an efficacious treatment, and it has largely replaced other bath treatmentsin several regions.
Internet e-mail discussion group for
Sealice Web site
lice biology and control
A World Wide Web site has beenestablished at The Caligus listserver is an e-mail discussion to host the Concerted Action Homepage.
interested in lice biology and control to provide and request information from others in the group. The group relies on people voluntarily workshops and conferences, the registerof persons interested in lice biology and control, a bibliography of sealiceliterature as well as contact details and (a) send an email to <[email protected]>, (b) leave the ‘subject’ line blank, and (c) type in the following command in the main CALIGUS first-name surname”. Do not include To leave the list, send the message “SIGNOFFCALIGUS” to <[email protected]>.
Contributions
<[email protected]> will send the message to all subscribers to the group. If you research projects, viewpoints, letters and whether it is more appropriate to send it back to newsletter. Please send details to Ms J.
everybody, or only to the individual who sent the message. The latter may avoid annoying Acknowledgement
This newsletter is funded under the European Union FAIR (aquaculture) research programme as part of a project
entitled ‘Biology and management in the control of lice on fish farms’ (contract number CT96-1615). The project is a
‘Concerted Action’ and so does not involve new research but rather facilitates the communication of information related to
the control of lice on fish farms. This is being achieved through providing a World Wide Web site and e-mail network,
hosting of meetings (workshops and conferences), establishment of a list of researchers, farmers and authorities interested
in lice control, producing a computerised bibliography, and publishing the bibliography, newsletter, and proceedings of
meetings.
The project is co-ordinated by Dr Mark J. Costello (EcoServe, Dublin) in partnership with Dr Geoffrey A. Boxshall
(Natural History Museum, London), Mr Kjell Maroni (KPMG, Lauvnes), Mr Per Gunnar Kvenseth (Norsk Hydro a/s), and
Dr Carmel Mothersill (Dublin Institute of Technology). Enquires about the project should be sent to:
[email protected]; Dr M. J. Costello, Ecological Consultancy Services Ltd, 17 Rathfarnham Rd, Terenure, Dublin
6W, Ireland; or any of the project’s partners.
Copyright statement. The information in Caligus may be published elsewhere without prior permission for non-profiting making purposes provided its source is clearly acknowledged. Recommended acknowledgement is“From Caligus, a newsletter funded under the EU FAIR programme”. EcoServe, December 1998 This newsletter is printed on recycled paper

Source: http://www.ecoserve.ie/projects/sealice/caligus5.pdf