Farms, Sea Lice & Wild Salmon:

atershed A Watershed Watch Report on Risk, atch Responsibility and the Public Interest December 2001 WSALMONW SOCIETY CONTENTS Foreword ...... 1 Summary ...... 3 Introduction ...... 4 Summary of Life History and Pathology ...... 5 Outbreaks of Sea Lice Worldwide ...... 8 The Broughton Archipelago Outbreak ...... 10 Concluding Remarks ...... 11 References ...... 13 Appendix A: Historical context of Salmon in BC ...... 16 Appendix B: Biology and Natural History of salmonis ...... 17 Appendix C: Current Methods of Prevention and Treatment ...... 20 Appendix D: Glossary ...... 25 Figure 1. Locations of salmon aquaculture tenures in British Columbia ...... 4 Figure 2. Life cycle of Lepeophtheirus salmonis ...... 5 Figure 3. Locations of outbreaks of sea lice, Lepeophtheirus salmonis, on wild fish and farmed fish in the world ...... 8 Figure 4. Salmon aquaculture tenures in the Broughton Archipelago ...... 10

ACKNOWLEGEMENTS Watershed Watch thanks those scientists and conservationists who have reviewed and otherwise supported this report, Alexandra Morton for sharing unpublished data and photos of lice-infested chinook, and the David and Lucile Packard Foundation, Endswell Foundation, Tides Canada Foundation, and Henry P. Kendall Foundation for generous and timely support. Front cover photo: Craig Orr Back cover photo: Courtesy of David Suzuki Foundation Design & production: Eye Design Inc.

Printed in Canada on paper with 30% post-consumer fibre, elemental chlorine free and processed chlorine free. ii Salmon Farms, Sea Lice & Wild Salmon Foreword

ife in British Columbia is intimately tied to the province’s L Pacific salmon. Salmon are a source of employment, food, recreation, culture – even the nutrients that sustain our ecosystems.

Recent declines of BC’s wild salmon have As the matter now stands, the responsi- gravely affected coastal communities. bility for informing the public falls too Fewer fish mean fewer opportu- often on the shoulders of the environ- nities and fewer jobs. For communities mental and academic communities. A already reeling from downturns in other Watershed Watch co-sponsored work- resource-extracting industries, salmon shop in March, 2000 identified signifi- declines are particularly damaging. cant gaps in our knowledge of environ- IT’S TIME TO mental, genetic, ecological and disease Not surprisingly, many coastal inhabi- ACKNOWLEDGE risks to wild salmon (www.sfu.ca/coastal- tants now look toward salmon farming studies). Scientists from around the THAT THE PUBLIC for income. But for what gain? And at world said that we must learn much what price? Evidence suggests that open IS NOT BEING more before permitting the salmon-farm- net-cage aquaculture poses risks to the ing industry to expand. ADEQUATELY health of BC’s wild salmon, to marine INFORMED ABOUT ecosystems, and to humans. The workshop’s findings were echoed prominently in a subsequent report by THE PERILS THAT Watershed Watch believes that British Canada’s Auditor General, which was Columbians deserve to know much ACCOMPANY especially critical of a perceived conflict more about those risks – including how THE SALMON- present-day choices for FARMING employment and industry can influence our environ- INDUSTRY. ment and well being. It’s time to acknowledge that the public is not being ade- quately informed about the perils that accompany the salmon-farming industry.

Typical open net-cage salmon farm on the British Columbia coast.

Photo courtesy of David Suzuki Foundation

A Watershed Watch Report on Risk, Responsibility and the Public Interest 1 between and Oceans’ role as To explore these and other concerns, protector of wild salmon, and its promo- Watershed Watch commissioned tion of salmon farming. fisheries biologist Dr. Diane Urban to research the sea lice and salmon farming Ireland’s Paddy Gargan delivered a key connection. Dr. Urban examined the lecture at the SFU workshop. Though biology of lice, the link between salmon Dr. Gargan is mild-mannered, his farming and sea lice outbreaks in wild message was not. In describing the link salmon—here, and elsewhere across the between salmon farming and sea lice globe—and the transmissions between outbreaks in wild trout and salmon, wild and farmed fish that inevitably he underscored the fact that the salmon accompany farming of salmon in open farm sea lice threat “can be greater than net-cage structures. biological or genetic threats.” Watershed Watch has incorporated and That message came to British Columbia summarized Dr. Urban’s biological find- WATERSHED in no uncertain terms in the summer of ings into a broader assessment of the sea 2001, when juvenile wild WATCH BELIEVES lice threat. Clearly, understanding the of the Broughton Archipelago (northeast THE PUBLIC IS lice threat requires a basic understanding of Vancouver Island) were severely of the biology and ecology of salmon ENTITLED TO infested by sea lice. For good reason, and lice. But to avoid being bogged public and media scrutiny focused on KNOW MUCH down in detail, while still providing the probable link between the outbreak, detail for those wishing it, Dr. Urban’s MORE ABOUT THE and the area’s densely-clustered salmon- full findings are included in the report’s farming industry. CONNECTION appendices. BETWEEN OPEN Curiously, Fisheries and Oceans Canada This report’s findings raise serious spokesman Don Noakes dismissed fears NET-CAGE doubts about the federal and provincial of a farm-salmon-to-wild-salmon link. governments’ wild salmon management SALMON FARMS Sea lice outbreaks were “natural” and intentions and/or abilities. This much is the public “is getting quite a biased view AND LICE certain: never has the public more of what’s happening,” he declared. But OUTBREAKS IN needed to know whether or not its no details were provided. own governments (municipal, federal, WILD SALMON. Watershed Watch believes the public provincial) are serious about protecting is entitled to know much more about one of the world’s few remaining abun- “what’s happening,” and much more dances of wild Pacific salmon. about the connection between open Craig Orr, Ph.D., Executive Director net-cage salmon farms and lice Watershed Watch, Coquitlam, BC outbreaks in wild salmon. December 2001 www.watershed-watch.org

2 Salmon Farms, Sea Lice & Wild Salmon Summary

his paper focuses on an environmental issue associated Twith open net-cage salmon aquaculture: sea lice infestation on wild salmon, and its link to lice coming from sea farms. The evidence suggests that wild salmon are vulnerable to farm-source sea lice, Lepeophtheirus salmonis, a parasite native to BC marine waters.

The paper sketches the basic biology of stressed group of fishes. Juvenile salmon lice, the parasitic relationship of lice to are particularly vulnerable; five lice can salmon, the effects of infection, and the debilitate a fish of 15 grams or less, and JUVENILE recorded occurrences of lice epizootics. 11 or more will kill it outright. SALMON ARE It provides a detailed summary (Appen- Despite the evidence implicating fish dices B-C) of the biology and natural his- PARTICULARLY farms, and despite the precarious plight tory of the sea louse, and of the pros and of Pacific salmon, the federal and VULNERABLE; cons of current lice-prevention and provincial governments seem reluctant treatment tactics. FIVE LICE CAN —or unable—to apply the precautionary DEBILITATE A A recent and severe lice outbreak in principle to the aquaculture industry. wild pink salmon (Oncorhynchus This report makes the case that Canada FISH OF 15 gorbuscha), in one of BC’s heaviest and British Columbia should do their GRAMS OR LESS, concentrations of salmon aquaculture, utmost to protect Pacific salmon—for the Broughton Archipelago, emphasizes the people of Canada, for the people of AND 11 OR MORE the need to prevent salmon farms from the world, for the future, and for the WILL KILL IT becoming lethal reservoirs of lice. fish themselves. OUTRIGHT. Though BC’s wild salmon have co- The matter is urgent. evolved with lice, the advent of fish farms appears to impact an already

Infected (and dead) smolt, taken July 31, 2001, Broughton Archipelago.

Photo by Alexandra Morton

A Watershed Watch Report on Risk, Responsibility and the Public Interest 3 Introduction

any people view salmon farming as a solution to the Meconomic woes now besetting BC’s coastal communities. Many others view salmon farming as a direct and serious threat to wild salmon and salmon habitat. This much is certain: wild Pacific salmon are in trouble, and they will not survive unless they receive our best stewardship.

Each and every threat, including those occurrences of sea lice outbreaks, or posed by a proposed expansion of an epizootics, evaluates the pros and cons WILD PACIFIC already extensive salmon farming of various treatments, and makes several SALMON ARE industry (Figure 1), must be carefully recommendations. considered. IN TROUBLE, This paper examines AND THEY the risk of salmon FIGURE 1. WILL NOT farm-source sea lice Locations of the active SURVIVE UNLESS infesting wild salmon. salmon aquaculture tenures Two principal questions in British Columbia. THEY RECEIVE are considered: Source: BC Assets & Lands, OUR BEST ■ To what extent Oct. 2001. Map courtesy of Living Oceans Society STEWARDSHIP. do salmon-farm infestations of sea lice spread to wild salmon stocks? and ■ Is government dealing with those risks in an appropriate manner?

The paper sketches the biology and natural history of the sea louse, Lepeophtheirus salmonis, its parasitic relationship to salmonids and the N resulting effects of infection on salmon, summarizes the recorded

4 Salmon Farms, Sea Lice & Wild Salmon Summary of Life History & Pathology

detailed overview of the life history and pathology of sea A lice is provided in Appendix B. In summary, the sea louse is a small parasitic copepod that undergoes a series of 10 life history stages, each characterized by a moult that takes it from egg to adult (Johnson and Albright 1991a).

The egg hatches into the first stage of A louse is infective at the free-swimming nauplius, moults to the second nauplius copepodid stage. The life cycle varies stage, then develops into a copepodid, from six weeks in the wild to eight before going through four chalimus weeks in the laboratory. Increases in HOST stages, a first and second stage of pread- water temperature shorten development ults, and then a final adult stage. The time, which is therefore of particular RESPONSES moults are characterized by gradual concern when ocean temperatures are INCLUDE changes as the undergoes modifi- rising—as has recently been the case. cations that enable it to live as a free Development time also varies with the INCREASED roaming parasite, feeding and breeding species of host. For example, sea lice STRESS AND on the surface of mucous-covered fish. develop faster on REDUCED IMMUNE FUNCTION…

FIGURE 2. AND EVENTUAL Life cycle of Copepodid DEATH Lepeophtheirus Nauplius 1 stage, salmonis 2 stages, free-swimming, free-swimming, non-feeding Diagram non-feeding courtesy of Thomas Schram

Preadult Egg Chalimus strings 2 stages, feeding and mobile 4 stages, attached & feeding on fish, but non-mobile Adult (female) feeding and mobile Scale bars: nauplius & chalimus = 0.1mm, preadult & adult = 1mm

A Watershed Watch Report on Risk, Responsibility and the Public Interest 5 ( salar) than on chinook salmon ties generally observed in wild popula- (Oncorhynchus tshawytscha). tions, lice don’t usually pose a serious fish heath risk (Nolan et al. 1999). Lice survival at most stages is reduced in lower salinities; e.g., at < 20 parts per Although many species of salmon are thousand (‰). At typical sea tempera- known hosts of L. salmonis, different tures, copepodids survive only a few days species appear to have different degrees without a host. of susceptibility to infection (MacKin- non 1998). Among Pacific salmonids Most organisms, including salmon, can (Nagasawa et al. 1993), pink salmon normally coexist with disease, viral, carry the highest loads (5.8 adult bacterial, or parasitic agents. Among the lice/fish on average) and highest preva- various mechanisms enabling the co- lence (92%). (Note: these data are from existence are natural selection for resist- a single season (1991) of sampling.) ance, acquired immunities, behavioral LESIONS OFTEN avoidance, and maintaining good health Experimental studies also suggest that PENETRATE (avoiding immuno-suppression). certain hosts are more susceptible than others. Copepodids are better at attaching DEEP INTO THE As a disease agent, L. salmonis does not to and surviving on sea (brown) trout usually cause epizootics, or widespread FLESH AND (Salmo trutta) than on Atlantic salmon, mortality (Wooten et al. 1982). Though but as preadults, their survival rate is SOMETIMES the prevalence of sea lice is often high, lower on than on Atlantic the number on individual fish is usually TO THE BONE… salmon. In other words, though copepodids low. Severe pathological effects are rarely DOZENS OF LICE experience more difficulty attaching to reported (Wooten et al. 1982). Atlantic salmon, once they do, their MAY HANG This has important implications for wild chance of surviving to reproductive age FROM THE FISH. salmon. Experimental studies indeed is higher (Dawson et al. 1998). suggest that at the low parasite intensi

Although many species of salmon are known hosts of L. salmonis, different species appear to have different degrees of susceptibility to infection.

6 Salmon Farms, Sea Lice & Wild Salmon (O. kisutch) are less suscep- of the cortisol response, it is not surpris- tible than either chinook or Atlantic ing that the initial host reaction to the salmon, and the species has a lower corti- copepodid attachment is a good indicator sol (stress index) response to early stage of whether or not the host will success- attachment (Johnson and Albright 1992). fully fight off infection (Johnson and Albright 1992; Gonzalez et al. 2000). Descriptions of the pathology of severely infested fish are graphic. Lesions often Ultimately, the fish’s ability to survive penetrate deep into the flesh and some- depends on the severity of the infection; times to the bone. The heads and dorsal a heavy lice load will cause host death. regions of some infested salmon are grey An 11-lice-per-fish intensity kills to whitish—where the skin has been juvenile Atlantic salmon weighing 15 g removed, and where dozens of lice may or less (Finstad et al. 2000). hang from the fish. Significant pathological damage on Sea lice may cause two physiological Atlantic salmon may result from as few SIGNIFICANT changes in their hosts. The primary as five adult lice per fish (Wooten et al. PATHOLOGICAL response is increased stress (Bjorn and 1982). In infected sea trout and Atlantic DAMAGE ON Finstad 1997; Poole et al. 2000) and salmon, no mortality occurred while reduced immune function (decreased the fish were infested with chalimus ATLANTIC lymphocyte activity). stage sea lice, but mortality increased SALMON MAY exponentially once sea lice reached the The second is complete osmoregulatory preadult stage (Grimnes and Jakobsen RESULT FROM failure, and eventual death (Jones et al. 1996; Finstad et al. 2000). AS FEW AS 1990; Grimnes and Jakobsen 1996). Given the evidence for the importance FIVE ADULT LICE PER FISH.

Fish infected with sea lice. Photo by Alexandra Morton

A Watershed Watch Report on Risk, Responsibility and the Public Interest 7 Outbreaks of Sea Lice Worldwide

ccurrences of sea lice outbreaks in wild salmon have been Oreported since the inception of salmon aquaculture in Ireland, Norway, Scotland, New Brunswick, Chile, and British Columbia (Figure 3) (Tully and Whelan 1993; Gargan 2000; Hogans and Trudeau 1989; Haya et al. 2001; Carvájal et al. 1998; Johnson et al. 1996).

In each case, salmonids were heavily likely caused by migration delay and infested with sea lice, with more than unusually high water temperatures in 60 lice per fish common, and as many as Alberni Inlet. Additional stress from several hundred lice per fish (Finstad et delayed migration, high temperatures, ALL SEA LICE al. 2000). All outbreaks were in areas and crowding likely further increased OUTBREAKS with salmon aquaculture operations. susceptibility to infection. Two aquacul- ture farms were in or near the Alberni IN IRELAND, In a 1990 lice outbreak, the sockeye Inlet (Figure 1), with one recently NORWAY, salmon returning to BC’s Somass River decommissioned. were infected (on average) with 300 lice SCOTLAND, per fish (Johnson et al. 1996). Most fish By contrast, few studies detail the NEW BRUNSWICK, had severe lesions. Many also died. In prevalence or intensity of sea lice on CHILE, AND contrast, spawning fish in 1992 and salmonids in areas free of aquaculture. 1993 showed far lower prevalence and One study in England reported a high BRITISH intensity rates. The 1990 outbreak was prevalence (89 and 81%) but low COLUMBIA WERE IN AREAS WITH

SALMON Norway Scotland AQUACULTURE British Columbia Ireland OPERATIONS. New Brunswick

FIGURE 3. Locations of outbreaks of sea lice, Lepeophtheirus salmonis, on wild fish and farmed fish in the world Chile (in Chile, these outbreaks were of the related flexispina) Map by Peter Bromley 8 Salmon Farms, Sea Lice & Wild Salmon intensity (<5.5 lice/fish) on wild sea sibility that infestations originated from trout (Tingley et al. 1997). The maxi- wild salmon populations. mum number of lice per fish was 45. Similar patterns of sea lice infection and Importantly, only one chalimus stage sea wild salmonid declines have occurred lice was found on 34 fish sampled in near salmon farms in western Scotland 1992 and 1993, which suggests a low and Norway (Gargan 2000). High lice transmission rate in areas having no infestations are believed to cause high salmon farms (e.g. Appendix B). mortality and abnormal behavior in Patterns of lice epidemics indicate that postsmolt sea trout. Highly-infested outbreaks on salmon farms can cause trout returned to their natal rivers only epidemics on wild salmonids that weeks after leaving them, perhaps in an migrate close to infected farms. Patrick attempt to escape infestation. Gargan, speaking in March 2000 in In Norway, the mortality rate of sea trout British Columbia, described sea lice postsmolts was calculated at 48 to 86% IN A 1990 problems in Ireland, Scotland and in two fjords that had both heavy lice Norway, and the evidence linking them LICE OUTBREAK, infestations and salmon farming activity. to salmon aquaculture (Gargan 2000). THE SOCKEYE Samples from farm areas (< 3 km away During the 1970s and ‘80s, the catch of from migration routes) contained up to SALMON Irish sea trout declined only gradually. 400 lice/fish, while those caught in areas RETURNING TO By 1989, many populations of sea trout without farms (>20 km away) carried a had collapsed entirely. Gargan (2000) median of just 2 lice/fish. BC’S SOMASS examined 52 rivers and discovered a RIVER WERE Scientists at the 1996 International strong correlation between lice intensity Council for the Exploration of the Sea INFECTED in wild trout, and the proximity of meeting also concluded that sea lice on recently-sited salmon farms. (ON AVERAGE) wild Irish, Scottish, and Norwegian Heavy and lethal infestations (>30 salmonids were highest near salmon WITH 300 LICE lice/fish) occurred on wild sea trout aquaculture facilities (Gargan 2000). PER FISH. postsmolts only near salmon farms. Though data on sea lice occurrence and Postsmolts from rivers near farms were intensity on BC’s fish farms are not infested with predominantly chalimus available, the European experience and stages of lice, indicating recent infection. the recent outbreaks in BC point to an In contrast, wild trout from rivers free of obvious-yet-preventable connection salmon farms were never heavily infest- between salmon farms and sea lice ed, nor did these fish experience stock outbreaks in wild fish. collapses. Gargan also ruled out the pos

A Watershed Watch Report on Risk, Responsibility and the Public Interest 9 The Broughton Archipelago Outbreak

n the first week of June 2001, ocean-bound juvenile pink I salmon migrating from coastal rivers through the islands north- east of Vancouver Island (the Broughton Archipelago) were discovered infested with unprecedented loads of L. salmonis.

Local biologist Alexandra Morton imme- mation will be available once the sam- diately collected samples of infected ples are analysed (Morton, pers. comm.). salmon (A. Morton, pers. comm.). Morton contacted the Department of Fish- Morton ran three transects (starting eries and Oceans to request they investi- from the Ahta and Kingcome rivers, and NEAR EACH gate the apparent epizootic. Additional Embly Lagoon) near where the fish had requests for help came from aboriginal ACTIVE FARM, been spawned, and followed their leaders and local residents. No outbreak migration route out of the archipelago AVERAGE LICE had ever before been reported in pink to the sea. She collected more than 600 salmon on BC’s coast. However, follow-up LOAD ROSE TO juvenile pink salmon at 44 sites. investigation by DFO has been limited. 10 PER FISH, From where the salmon had emerged Moreover, DFO spokesmen claim it is very A LETHAL LOAD from the gravel in their natal stream to common for pink salmon to be infected, a point just short of a salmon farm, Mor- ESPECIALLY FOR refuted the suggestion that the fry were ton found that the pinks had from zero infected from outbreaks on nearby farms, YOUNG AND to six lice. Near each active farm, aver- and stated that wild stocks infect farmed SMALL FISH. age lice load rose to 10 per fish (Morton, fish, not vice-versa (CBC Radio, June 21, unpublished data), peaking (on average) 2001; Times Colonist, June 27, 2001). at 23 per fish in the “plume” seaward of salmon farms. These are lethal levels, especially for such young and small fish (approximately 3 cm in length).

Morton described the fish as ravaged and Queen Charlotte Strait emaciated, and covered in black pin- prick rash, with bleeding eyes; they were also raked with what appeared to be teeth marks (long, parallel trenches dug out of their flesh; Morton, pers. comm.). The source of infection by a copepodid can be deduced by using the backdating FIGURE 4. Salmon aquaculture tenures in technique based on known developmen- the Broughton Archipelago tal rates and place of capture. This infor- Map courtesy of Living Oceans Society

10 Salmon Farms, Sea Lice & Wild Salmon Concluding Remarks

ike wild salmon elsewhere, BC’s salmon, mainly the L juveniles, are at risk from sea lice infestations originating from open net-cage salmon farms. We know this to be true from the biology of the .

We also know this from research from are at substantial risk to lice infestations BC and around the world showing that emanating from salmon farms. As few as severity of infestation rates on wild five lice may debilitate a fish of 15 grams salmonids increases with proximity or less; 11 or more will kill it outright. to farms. Government must acknowledge and SINCE FISH Though parasites are always present address the lice risk. What’s needed is: FARMS ARE in BC’s coastal waters—and (in low ■ more science (including DNA tracking MADE OF NETS, numbers) on wild salmon—fish farms of lice); may offer ideal conditions for lice to ■ an effective risk management and THEY PERMIT flourish (stress, crowding, lights). Since response plan that considers variation VECTORS TO farms are made of nets, they permit in infestation susceptibility among vectors to pass freely to wild fish and PASS FREELY salmon species; marine ecosystems. ■ a transparent reporting and monitoring TO WILD FISH Migrating salmon frequently pass close program, and; AND MARINE to (and through) salmon farms. Such ■ an honest examination of the efficacy ECOSYSTEMS. close proximity exposure is bound to of currently-used lice prevention and increase with the anticipated expansion treatment methodology. of the industry. Clearly, juvenile salmon

Infected (and dead) Pink salmon smolt, taken in June 2001, Tribune Channel and Old Pass.

Photos by Alexandra Morton

A Watershed Watch Report on Risk, Responsibility and the Public Interest 11 To assist with this latter task, Watershed left to be determined is how to imple- Watch provides a review of current lice ment the policy, and still allow the prevention and treatment methodologies planned expansion of the aquaculture (Appendix C). If anything, the review industry. If Canada maintains that it is identifies major deficiencies in how committed to the precautionary princi- some jurisdictions attempt to prevent ple (Department of Fisheries and Oceans and/or deal with lice outbreaks. 2000), it must show more leadership in how it deals with the risks posed by Many of the available treatments are open net-cage aquaculture. It must learn either ineffective (e.g., peroxide), or from the experiences of other countries, severely damaging to fish and marine and not deny or trivialize the risks. It environments (e.g., should also weigh risks against the full and other neurotoxins). Whole bay value of wild salmon. fallowing, which breaks the lice life A GOVERNMENT cycle, and which lacks the baggage of A government that is truly concerned biocides, may offer the greatest promise with the public interest cannot support THAT IS TRULY of reducing lice risks. Fallowing by the expansion of salmon farming—until CONCERNED itself, however, will not eliminate the farming can be done without harm to problem. wild fish and fish habitat. Government WITH THE may also have to concede that wild and Canada is currently finalizing a much- PUBLIC INTEREST farmed salmon cannot coexist, unless we anticipated wild salmon policy. What’s CANNOT SUPPORT adopt closed-containment methodology. THE EXPANSION OF SALMON FARMING.

The 1996 Salmon Aquaculture Review lacks a mechanism for assessment of the risks posed to wild salmon of sea lice infestations emanating from salmon farms.

Photo by Kim Wright

12 Salmon Farms, Sea Lice & Wild Salmon References

Anonymous. 1998. Recommendations leading Carvájal, J., L. Gonzalez, M. George-Nascimen- to development of pest management plans to. 1998. Native sea lice (Copepoda: Caligi- for sustainable sea lice control in British dae) infestation in salmonids reared in net- Columbia. Prepared by BC Ministry of pen systems in southern Chile. Aquaculture Fisheries, Ministry of Environment, Lands 166: 241-246. and Parks, Health Canada, and BC Salmon Collier, L.M. and E.H. Pinn. 1998. An assess- Farmers Association. p. 23. ment of the acute impact of the sea lice treat- Barth, R. H. and R. E. Broshears. 1982. ment on a benthic community. The invertebrate world. Saunders College J. Exp. Mar. Biol. Ecol. 230: 131-147. Publishing. Philadelphia. Costelloe, M., J. Costelloe, and N. Roche. 1996. BC Fisheries. The 1999 British Columbia Planktonic dispersion of larval salmon-lice, industry in review. Victoria. p. 8. Lepeophtheirus salmonis, associated with cultured salmon, Salmo salar, in Western Birkeland, K. 1996. Consequences of premature Ireland. J. Mar. Biol. Ass. UK. 76: 141-149. return by sea trout (Salmo trutta) infested with the salmon louse (Lepeophtheirus salmo- Dawson, L.H.J., A.W. Pike, D.F. Houlihan, and nis Krøyer): migration, growth, and mortali- A.H. McVicar. 1997. Comparison of the ty. Can. J. Fish. Aquat. Sci. 53: 2808-2813. susceptibility of sea trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.) to sea Bjorn, P.A. and B. Finstad. 1997. The physiolog- lice (Lepeophtheirus salmonis (Krøyer, 1837)) ical effects of salmon lice infection on sea infections. ICES J. Mar. Sci. 54 (6): 1129- trout post smolts. Nord. J. Freshw. Res. 73: 1139. 60-72. Department of Fisheries and Oceans. 2000. Bjorn, P.A. and B. Finstad. 1998. The Wild salmon policy: A discussion paper. development of salmon lice (Lepeophtheirus Canada. salmonis) on artificially infected post smolts of sea trout (Salmo trutta). Can. J. Zool. 76: Finstad, B., P.A. Bjorn, A. Grimnes and N.A. 970-977. Huidsten. 2000. Laboratory and field investi- gations of salmon lice (Lepeophtheirus salmo- Brandal, P.O. and E. Egidius. 1977. Preliminary nis) infestation on Atlantic salmon (Salmo report on oral treatment against salmon lice, salar L) postsmolts. Aquat. Res. 31: 795-803. Lepeophtheirus salmonis, with Neguvon. Aquaculture 10: 177-178. Fraser, J. 2000. Opening remarks. In Proceed- ings of the Speaking for the Salmon work- British Columbia Environmental Assessment shop: Aquaculture and the protection of wild Office. 1999. Salmon Aquaculture Review: salmon. Edited by P. Gallaugher and Fish Health. C. Orr. Simon Fraser University, Burnaby, Bron, J.E., C. Sommerville and G.H. Rae. 1993. BC. p. 5-7. Aspects of the behaviour of copepodid larvae Gargan, P. 2000. The impact of the salmon of the salmon louse Lepeophtheirus salmon louse (Lepeophtheirus salmonis) on wild (Krøyer, 1837). In Pathogens of wild and salmonid stocks in Europe and recommen- farmed fish: sea lice. Edited by G.A. Boxshall dations for effective management of sea lice and D. Defaye. Ellis Horwood. London. on salmon farms. In Proceedings of the p. 125 – 142. Speaking for the Salmon workshop: Aqua- culture and the protection of wild salmon. Edited by P. Gallaugher and C. Orr. Simon Fraser University, Burnaby, BC. p. 37-45.

A Watershed Watch Report on Risk, Responsibility and the Public Interest 13 Gonzalez, L., J. Carvájal, M. George-Nascimen- Johnson, S.C. and L.J. Albright. 1992. Compar- to. 2000. Differential infectivity of Caligus ative susceptibility and histopathology of the flexispina (Copepoda, Caligidae) in three host response of naïve Atlantic, chinook, farmed salmonids in Chile. Aquaculture 183: and coho salmon to experimental infection 13-21. with Lepeophtheirus salmonis (Copepoda: Calgidae). Dis. Aquat. Org. 14: 179-193. Grant, A.N. and J.W. Treasurer. 1993. The effects of fallowing on caligid infestations on Johnson, S.C. 1992. A report on the sea lice farmed Atlantic salmon (Salmo salar L.) in symposium of the First European Confer- Scotland. In Pathogens of wild and farmed ence on Crustacea, Paris, France, August 31 fish: sea lice. Edited by G.A. Boxshall and D. to September 5, 1992. Prepared for BC Defaye. Ellis Horwood. London. p. 255-262. Ministry of Agriculture, Fisheries and Food. Victoria, BC. Pp. 45 + app. Grimnes, A. and P.J. Jakobsen. 1996. The physi- ological effects of salmon lice infection on Johnson, S.C. 1993. A comparison of develop- post-smolt of Atlantic salmon. J. Fish Biol. ment and growth rates of Lepeophtheirus 48: 1179-1194. salmonis (Copepoda: Caligidae) on naïve Atlantic (Salmo salar) and Chinook Haya, K., L.E. Burridge, B.D. Chang. 2001. (Oncorhynchus tshawytscha) salmon. In Environmental impact of chemical wastes Pathogens of wild and farmed fish: sea lice. produced by the salmon aquaculture indus- Edited by G.A. Boxshall and D. Defaye. Ellis try. ICES J. Mar. Sci. 58: 492-496. Horwood. London. Pp. 68-82. Heuch, P.A., A. Parsons, and K. Boxaspen. 1995. Johnson, S.C., R.B. Blaylock, J. Elphick, and : A possible K.D. Hyatt. 1996. Disease induced by the sea host-finding mechanism in salmon louse louse (Lepeophtheirus salmonis) (Copepoda: (Lepeophtheirus salmonis) copepodids? Caligidae) in wild Can. J. Fish. Aquat. Sci. 52: 681-689. (Oncorhynchus nerka) stocks of Alberni Inlet, Hogans, W.E. and D.J. Trudeau. 1989. Caligus British Columbia. Can. J. Fish. Aquat. Sci. elongates (Copepoda: Caligoida) from 53: 2888-2897. Atlantic salmon (Salmo salar) cultured in Jones, M.W., C. Sommerville, and J. Bron. 1990. marine waters of the Lower Bay of Fundy. The histopathology associated with the Can. J. Zool. 67: 1080-1082. juvenile stages of Lepeophtheirus salmonis Jackson, D., S. Deady, Y. Leahy, and D. Hassett. on the Atlantic salmon, Salmo salar L. J. Fish 1997. Variations in parasitic caligid infesta- Dis. 13: 303-310. tions on farmed salmonids and implications Kabata, Z. 1979. Parasitic Copepoda of British for their management. ICES J. Mar. Sci. 54: fishes. The Ray Society, London. 1104-1112. Kabata, Z. 1988. Copepoda and . Johnson, S. C. and L. J. Albright. 1991a. In Guide to the parasites of fishes of Canada. The developmental stages of Lepeophtheirus Part II. Crustacea. Edited by L. Margolis and salmonis (Krøyer, 1937) (Copepoda: Z. Kabata. Can. Spec. Publ. Fish. Aquat. Sci. Caligidae). Can. J. Zool. 69: 929-950. No. 101. p. 3-127. Johnson, S. C. and L. J. Albright. 1991b. MacKinnon, B.M. 1998. Host factors important Development, growth, and survival of in sea lice infections. ICES J. Mar. Sci. 55: Lepeophtheirus salmonis (Copepoda: 188-192. Caligidae) under laboratory conditions. J. Mar. Biol. Assoc. U.K. 71: 425-436.

14 Salmon Farms, Sea Lice & Wild Salmon Nagasawa, K., Y. Ishida, M. Ogura, K. Tadokoro Tingley, G.A., M.J. Inves, and I.C. Russell. 1997. and K. Hiramatsu. 1993. The abundance and The occurrence of lice on sea trout (Salmo distribution of Lepeophtheirus salmonis trutta L.) captured in the sea off the East (Copepoda: Caligidae) on six species of Anglian coast of England. ICES J. Mar. Sci. Pacific salmon in offshore waters of the 54: 1120-1128. North Pacific Ocean and Bering Sea. In Treasurer, J.W., S. Wadsworth, and A. Grant. Pathogens of wild and farmed fish: sea lice. 2000. Resistance of sea lice, Lepeophtheirus Edited by G.A. Boxshall and D. Defaye. Ellis salmonis (Krøyer), to to Horwood. London. p. 166-178. farmed Atlantic salmon, Salmo salar L. Nolan, D.T., P. Reilly, and S.E. Wendelaar Aquacult. Res. 31: 855-860. Bonga. 1999. Infection with low numbers of Tully, O. 1989. The succession of generations the sea louse Lepeophtheirus salmonis induces and growth of the Caligid Caligus stress-related effects in postsmolt Atlantic elongates and Lepeophtheirus salmonis salmon (Salmo salar). Can. J. Fish. Aquat. parasitising farmed Atlantic salmon smolts Sci. 56: 947-959. (Salmo salar L.). J. Mar. Biol. Ass. U.K. 69: Office of the Auditor General. 2000. 279-287. The Effects of Salmon Farming in British Tully, O. and K.F. Whelan. 1993. Production of Columbia on the Management of Wild nauplii of Lepeophtheirus salmonis (Krøyer) Salmon Stocks. Report of the Auditor Gener- (Copepoda: Caligidae) from farmed and wild al of Canada. December, 2000. salmon and its relation to the infestation of Poole, W.R., D. Nolan, and O. Tully. 2000. wild sea trout (Salmo trutta L.) off the west Modelling the effects of capture and sea lice coast of Ireland in 1991. Fisheries Research (Lepeophtheirus salmonis (Krøyer)) infesta- 17: 187-200. tion on the cortisol stress response in trout. Tully, O., W.R. Poole, K.F. Whelan and S. Aquacult. Res. 31: 835-841. Merigoux. 1993. Parameters and possible Raynard, R.S., J.A. King, A.L.S. Munro, I.R. causes of epizootics of Lepeophtheirus Bricknell, W. Melvin, C. Sommerville and salmonis (Krøyer) infesting sea trout (Salmo P. Reilly. 1995. The development of a vaccine trutta L.) off the west coast of Ireland. for the control of sea lice Lepeophtheirus In Pathogens of wild and farmed fish: sea salmonis and Caligus elongates in Atlantic lice. Edited by G.A. Boxshall and D. Defaye. salmon Salmo salar. Poster presented at the Ellis Horwood. London. p. 202-218. European Association of Fish Pathologists White, H. C. 1940. Sea Lice (Lepeophtheirus) 7th International Conference, Palma de and death of salmon. J. Fish. Res. Bd. Can. Mallorca, Spain, September, 1995. 5 (2): 172-175. Ritchie, G., A.J. Mordue, A.W. Pike, and G.H. White, H.C. 1942. Life history of Lepeophtheirus Rae. 1993. The reproductive output of salmonis. J. Fish. Res. Bd. Can. 6: 24-29. Lepeophtheirus salmonis adult females in relation to seasonal variability of temperature Wooten, R., J.W. Smith, and E.A. Needham. and photoperiod. In Pathogens of wild and 1982. Aspects of the biology of the parasitic farmed fish: sea lice. Edited by G.A. Boxshall copepods Lepeophtheirus salmonis and and D. Defaye. Ellis Horwood. London. Caligus elongatus on farmed salmonids, and p. 153-165. their treatment. Proc. Roy. Soc. Edin. 81B: 185-197. Spencer, R.J. 1992. The future for sea lice con- trol in cultured salmonids: a review. Prepared for the Marine Working Group of Scottish Wildlife and Countryside Link. p. 11.

A Watershed Watch Report on Risk, Responsibility and the Public Interest 15 Appendix A: HISTORICAL CONTEXT OF SALMON AQUACULTURE IN BC

The story of salmon in BC is inextricably As with many new industries, there were linked to BC’s history and culture. Salmon few regulations. The industry expanded sustained First Nations communities and from 10 farm tenures in 1984, to 135 in built an industry for four generations of 1989. Fifty companies were involved. settlers and their descendents. Communities By the late ‘80s, the public expressed serious arose and thrived on the abundance and concerns about potential impacts salmon richness of salmon. farms were having on the environment and But today—for many reasons well known to on wild salmon stocks. The public’s British Columbians—salmon are in trouble. concerns led to the formulation of the Declines in stocks have threatened the liveli- first industry regulations and management hood of many of BC’s inhabitants, especially practices. along the province’s still-rich coast. Throughout the 1990s, the plight of wild Recently, many coastal inhabitants have salmon worsened. Many stocks became sought another way to bolster employment threatened, and the public’s concern about and meet world demand for BC salmon: by the impacts of fish farms escalated. The culturing salmon in sea netpens. Salmon provincial government of the day imposed a aquaculture was first practised in BC in the moratorium on industry expansion. BC’s 1970s. It was, at first, a marginal enterprise Environmental Assessment Office appointed but, by the 1980s, government and others a technical and public committee to study viewed it as an economically viable alterna- and report on BC’s salmon aquaculture tive for an increasingly troubled commercial industry. The Salmon Aquaculture Review salmon . (SAR), produced in 1996, was subsequently The federal government’s Department of accepted by the BC government. The SAR’s Fisheries and Oceans, mandated with technical committee concluded that salmon protecting and conserving wild salmon, farming—as practised in BC and at current approved salmon farming in BC, originally (1997) levels—posed little environmental for coho and chinook salmon. When it risk, but nevertheless made 49 recommenda- became apparent that these wild BC species tions to reduce risks and to build public did not adapt particularly well to farming, confidence (Fraser 2000). the provincial government, now responsible The resulting policy framework had several for the management and development of the key elements, including: aquaculture industry, approved the importa- ■ Conventional salmon farms should be tion of Atlantic salmon. capped at 121; The Atlantic salmon is a species readily ■ Five new freshwater and five new adapted to domestication, and today, saltwater tenures should be made available Atlantics comprise over 75 percent of BC’s to stimulate the developing of “green” farmed salmon (http://www.bcfisheries.gov. and/or closed containment facilities; bc.ca/com/aqua/finfish.html).

16 Salmon Farms, Sea Lice & Wild Salmon ■ A new and strictly enforced waste manage- Today’s 121 marine salmon tenures are ment regime should be introduced; mostly located in and around the northeast ■ Farms should be required to implement and west coasts of Vancouver Island approved escape prevention and recovery (Figure 1). They are owned and operated by methods; 16 companies (http://www.bcfisheries.gov. bc.ca/com/aqua/finfish.html). ■ A two-year action plan to relocate poorly sited and inactive farms should BC is now the world’s fourth largest produc- be introduced; er of farmed salmon—after Norway, Chile, ■ The application and tenure referral and the UK. Seventy-five percent of BC processes should be streamlined; farmed salmon is exported, with 90 percent going to the US. In 1999, the salmon aqua- ■ A fish health code should be implemented; culture industry employed nearly 1800 and people and contributed 18 percent of the ■ The industry should be evaluated after two total weight of seafood harvested in the years, to determine how effectively it province (BC Fisheries 1999). That amount- meets environmental and technological ed to 48 percent of the total landed value. standards, and community expectations. The weight and value of the province’s Conspicuously lacking from the SAR was an commercial salmon harvest continues its assessment of the risks posed to wild salmon 10-year decline, and are now 6.5 percent of sea lice infestations emanating from and 4 percent, respectively. salmon farms. Appendix B: BIOLOGY & NATURAL HISTORY OF LEPEOPHTHEIRUS SALMONIS

The parasitic copepod, Lepeophtheirus SEA LICE DEVELOPMENT salmonis, is well known by invertebrate L. salmonis undergoes a series of ten life specialists and fisheries personnel (described history stages, each characterized by a moult in Kabata 1979, 1988). Commonly known that takes it from egg to adult (Johnson and as a sea louse, its marine distribution Albright 1991a). extends over the northern hemisphere. The egg hatches into the first stage of It favours salmonids, upon which it lodges nauplius, moults to the second nauplius and upon whose flesh it feeds. stage, then develops into a copepodid, before Reports from early in the 20th century going through four chalimus stages, a first describe infestations on wild salmon, but and second stage of preadults, and then a some of these reportings may have confused final adult stage. morphologically similar species, e.g., Caligus The moults are characterized by gradual clementis and C. elongatus (White 1940, changes as the animal undergoes modifica- 1942). Accurate identification has been tions that enable it to function as a free improved with the publication of the com- roaming parasite, feeding and breeding on plete description of the life history of the the surface of mucous-covered fish. species by Johnson and Albright (1991a).

A Watershed Watch Report on Risk, Responsibility and the Public Interest 17 L. salmonis is well adapted to life as an may be the case if the two are sharing the ectoparasite (Kabata 1979): the adaptations same stratum of the water column (Heuch include a flattened body covered by a shield, et. al. 1995). and the modification of swimming legs and Wooton et. al. (1982) observed that other appendages into grasping or feeding L. salmonis usually attaches to the dorsal or appendages. The reproduction segment pelvic fins, and around the anus, although in (genital complex) also becomes well devel- laboratory experiments, the most common oped, taking on larger size and different site of attachment was on the gills, with shape in the female, with the abdomen other areas of secondary importance reduced to one small segment. (Johnson and Albright 1991b). Throughout its development, the animal Once attached, the copepodid undergoes a also experiences a reduction in its armature moult to the first chalimus stage, where it (Johnson and Albright 1991a), since cope- attaches to the host through a filament pods attached to fish need fewer defensive emerging from the front (Wooten et al. structures than do free-swimming copepods. 1982). This filamental attachment remains No natural lice predators are known (John- throughout the four chalimus stages, and in son and Albright 1991b). males up to the first preadult stage, thereby One reason the species is well known is that limiting the parasite’s mobility (Johnson and it is so obvious on fish. Lice are relatively Albright 1991b). By the second preadult large parasites, and their movements can be stage, the filament is detached and the para- clearly observed. Females are the larger, site is fully mobile. Many preadult and adult averaging 9.96 ± 1.55 mm (1 SD) in length, lice are found on the head and dorsal while males average 5.4 ± 0.48 mm (Kabata regions of their hosts (Wooten et al. 1982; 1988). Bjorn and Finstad 1999). The sea louse is infective at the free-swim- Development times of each of the stages is ming copepodid stage, and this is when it known through laboratory experiments attaches to a host, if one is encountered. where eggs were incubated and allowed to How it finds and attaches itself to a host is develop under different temperature and not exactly known, but it may rely on a salinity regimes (Johnson and Albright combination of light and low pressure that 1991b). Average egg development time attract fish to surface waters, and on a (from egg extrusion to hatching) ranged mechanical vibration generated by a host from 17.5 d at 5ºC. to 5.5 d at 15ºC. (Bron et al. 1993). The average development time from hatch- The copepodids are positively phototactic ing to the infectious copepodid stage was and exhibit a daily vertical migration, rising 87.4 h at 10ºC to 44.8h at 15ºC. Field from the deeper waters to the surface during observations corroborate the hatching to the day, and sinking at night (Heuch et al. copepodid times on Atlantic salmon: 63 1995). It is possible that wild salmon, which hours at a temperature of 11ºC, but as little generally avoid the surface during the day, as 46 h at 12ºC (Wooton et. al. 1982). may pass through the layer of sea lice as The first adults to appear after an infection they slip into deeper waters with the advent are males, at about 40 days after egg of light. Tiny copepodids caught up in the extrusion in 10ºC water. The first adult vortices created from a moving fish may be females followed 12 days later (52 d post more likely to find opportunities to attach to egg extrusion). the host than if the host were resting, as

18 Salmon Farms, Sea Lice & Wild Salmon The total generation time of the life cycle The eggs mature in long external ovisacs, varies from 6 weeks (observed in the field) which protrude from the female’s genital to 7.5 to 8 weeks at 10ºC in the laboratory complex segment. Sea temperature has an (Wooten et. al. 1982). From May to October effect on the number of eggs produced and a succession of three or four generations can on egg size: at lower temperatures, such as occur with the population peaking at the in winter, more eggs are produced, but are end of the summer. Gravid (ovigerous) smaller than in warmer temperatures females may be found at any time in the (Ritchie et al. 1993). Egg numbers vary. year, but it is not known if they reproduce The average number of eggs per louse on year round (Wooten et al. 1982). Atlantic salmon is 344 eggs per female That increases in water temperature shorten (Johnson and Albright 1991b), but, the development time is a vital considera- occasionally, a female will have as many tion in periods of rising ocean temperatures. as 700 (Wooten et al. 1982). In general, this climate trend could increase Fecundity of female lice may also be influ- the production rates of sea lice. Tully et al. enced by the host species. For example, (1993) estimate that the elevated sea female sea lice on Atlantic salmon produced temperatures from 1989 to 1991 increased almost twice as many eggs as those on chi- the potential number of generations to nook salmon (Johnson 1993). Most of this almost seven generations per year from increase was correlated to the greater body 5.5 generations from 1985 to 1988. size achieved by female lice on Atlantic salmon (compared to chinook salmon). INFLUENCE OF HOST SPECIES Researchers suspect these differences are ON SEA LICE DEVELOPMENT attributable to nutritional or non-specific Sea lice develop faster on Atlantic salmon host mechanisms (Johnson 1993). than on chinook salmon: adult males appear on Atlantic salmon up to 25 days post Survival infection, while taking about 15 days longer The mortality rates sea lice suffer through- to appear on chinook salmon (Johnson out their development stages can be quite 1993). Sea lice development is also slower high. Mortality from chalimus stage to pre- on sea trout compared to Atlantic salmon adult has been reported at 37% on sea trout (Bjorn and Finstad 1999). and 43% on Atlantic salmon (Bjorn and Finstad 1998; Grimnes and Jakobsen 1996). Reproduction Bjorn and Finstad (1998) note a density- Reproduction in L. salmonis follows the dependent effect on lice survival. Lice general pattern of (described in parasitizing more heavily infected hosts Barth and Broshears 1982): males grasp had lower survival rates than those on less females and transfer their spermatophore to infected hosts. the female’s seminal receptacles through Lice survival at most stages is reduced in their gonadal pores. Sperm enter the female lower salinities, e.g., at < 20‰ (Johnson reproductive tract and fertilize eggs posi- and Albright 1991b). In laboratory tests, tioned in the oviducts. Males mate with both copepodids generally did not develop in stages of pre-adult females, as well as with salinities of less than 30‰. Survival upon adult females (Johnson and Albright 1991b). entering freshwater (attached to their spawning hosts) is a few days (Kabata 1979), though there are reports of sea lice

A Watershed Watch Report on Risk, Responsibility and the Public Interest 19 surviving for up to 21 days (Wooten et al. after several weeks in freshwater, and return 1982). In marine water, copepodids are short to sea either completely free of lice, or lived if they do not find a host: in experi- bearing greatly reduced numbers (Birkeland ments and in the field, free swimming cope- 1996). Infested pink salmon fry have been podids survived up to 8 d at favorable tem- observed in BC’s coastal waters pooling peratures and salinity, but only 2 and 4 days underneath a waterfall (A. Morton, pers. at a water temperature of 12ºC (Wooton comm.), possibly for the same purpose. 1982; Johnson and Albright 1991b). At least The life span of adults is not known, but one species of salmonid may be able to adult males of the congeneric L. pectoralis exploit the lice’s intolerance to low salinity: were found to live up to 101 days (Tully et some heavily infested sea trout postsmolts in al. 1993). Europe return to rivers, lose their lice loads Appendix C: CURRENT METHODS OF PREVENTION AND TREATMENT

PREVENTION single generation sites (Jackson et al. 1997). The time-honored saying, “an ounce of Monitoring data have allowed scientists to prevention is worth a pound of cure,” is investigate the success of different manage- certainly true for sea lice infestations. Once ment strategies. In 1994, after farm man- lice are attached to fish, disease quickly agers began practising prevention and treat- invades; in six weeks there may be wide ment, lice levels on farms declined (Jackson spread mortality of salmonids. In many et al. 1997), infections in wild salmon cases, especially if a farm is unprepared for declined, and wild salmon stocks recovered, the occurrence, treatment is not readily although not to pre-1980s numbers (Gargan available and the operator suffers high loss- 2000). es. In BC this may be particularly relevant if A recent BC, federal government and salmon sea lice on salmon farms is not perceived as industry report recommended the need for a a serious risk: as late as 1998, there were sea lice management plan that includes less than five reports of serious outbreaks on preventative techniques: clean nets, fallow- BC sea farms (Anon. 1998). ing (at least 3 months), single-year-class net There are ways of minimizing the risk of sea pens, appropriate siting (avoiding pink lice propagation in sea pens. Commencing salmon migration routes), healthy smolts, in 1991, salmon farm managers in Ireland lower fish densities, and vaccines (Anon. were required to sample for lice 14 times per 1998). The methods that will be discussed year (Jackson et al. 1997). When monitoring here include fallowing, single bay manage- showed high lice levels, husbandry practices ment, lower host densities, siting, and sin- were implemented aimed at reducing the lat- gle-year-class management. It should be eral and vertical transmission of sea lice noted that any of these techniques are most infection, through single bay management, a effective if they are practised simultaneously, production cycle of 14 to 18 months, and by all farms operating in the bay or channel.

20 Salmon Farms, Sea Lice & Wild Salmon Single Bay Management should cover the life cycle of the parasite Where more than one company operates from the egg stage to the maximum time of within a bay, information on infections and survival of copepodids (at least 30 days management must be shared, or control during winter months; Grant and Treasurer efforts will be ineffective. Recommendations 2000). In Europe, where sea lice infections on monitoring, information sharing, and have been severe, fallowing is recommended coordinating and synchronizing treatments because it reduces the need for expensive have been made by provincial officials and and environmentally questionable treat- industry. Costs, and concerns over confiden- ments. In BC, the salmon aquaculture tiality, remain stumbling blocks. Manage- industry is concerned about the reduction ment tactics such as fallowing must also be in profits potentially suffered by loss of on a bay-to-bay basis, as the larvae from one production for those months, and uses these farm has the potential to infect a nearby potential losses to argue for expansion of farm, rendering the efforts of one farm’s licenses (Anon. 1998). management less effective. Siting Fallowing The question of whether farm fish are infec- Fallowing once per year for at least six tive reservoirs or victims of infection by wild months improves wild sea trout survival salmon is immaterial to the question of (Gargan 2000). Copepodids have up to eight where farms should be sited: not within or days in which to find a host (Wooton et al. near wild salmon migration routes. Other 1982; Johnson and Albright 1991b). Leaving known factors affecting sea lice biology a site fallow allows the sea lice cycle to be should be considered when choosing a site, broken (Grant and Treasurer 1993). The including the known effect of decreased infective stage dies out, before new hosts water temperature and decreased salinity on can be infected; as a consequence, the sea growth, development and survival (Wooten lice population must start anew with each et al. 1982; Johnson and Albright 1991b). production cycle. The strength of this Stratified water, such as found in channels management tool depends on the density or , may afford relief to fish that of larvae dispersed in the area, which are swim up through the fresh water and are presumably diminished by eliminating the able to delouse themselves (Spencer 1992). source at the farm. Dispersal patterns of larvae are best predict- Examples from elsewhere show the positive ed by current patterns, and to minimize the effects of fallowing on lice levels and aggregation of larvae into a densely packed salmonid survival (Grant and Treasurer area, siting decisions must consider the 1993; Gargan 2000). In both Scotland and hydrography of a bay (Costelloe et al. 1996). Ireland, sea trout in rivers next to sea farms survived better in years when the farms were Density fallowed (Gargan 2000). In New Brunswick, Disease rates are correlated to stocking a fallowing program was introduced in 2000 densities (Spencer 1992). Mobile stages of to combat recent outbreaks of the closely L. salmonis are able to transfer to other fish related but more prevalent Caligus clemensis within and between pens, with transfer like- (Haya et al. 2001). lihood greatly enhanced by high densities (Johnson 1992). Industry argues that restric- Recommended duration of fallowing fre- tions on expansion within the industry force quency and duration vary, but at a minimum companies to maximize fish densities in

A Watershed Watch Report on Risk, Responsibility and the Public Interest 21 pens (Anon. 1998). If outbreaks on farms Most chemical therapeutants are adminis- follow patterns elsewhere, industry may tered in a bath treatment form, although have no choice but to adopt new strategies. some, such as the ivermectin, are given oral- ly. A bath treatment reduces the volume of Single Age Class the net pen with an underlying tarp that is The principle of raising single age classes of drawn up around the netpen. Dosages often fish in net pens is based on the observation have a narrow margin of error, and estimat- that newly introduced smolts are more sus- ing the dosage requires accurate estimation ceptible to infection by sea lice than other of the volume of the bag containing the net age classes of fish. In a Scottish farm where pen, knowing the temperature dependencies smolts were stocked alongside pens with of the chemicals, and knowing how long to older year class fish carrying lice, smolts continue the bath treatment, before releasing were heavily infested with copepodids within it into the environment. Other concerns three days (Grant and Treasurer 1993). include resistance of lice to chemical Comparisons of lice levels from fish raised therapeutants, and the logistical difficulties in single generation farms with those from involved; both are also labour intensive and multi-generation farms confirm this is an expensive (Grant and Treasurer 1993). appropriate technique (Jackson et al. 1997). Hydrogen Peroxide Experimental evidence supporting rearing one age class as a lice control technique is Hydrogen peroxide is pumped into the sea found in Bron et al (reported in Johnson cage to a known concentration based on 1992) where infection levels at single year calculated volume of water held in a tarp class sites were lower than those at multiple enveloping the netpen. Although hydrogen year class sites. However, the site numbers peroxide is a recognized household product, were low (n = one for multiple year sites), it is potentially lethal to fish (Johnson and by the second year, even single year 1992); recommended concentration must class sites had heavy infestations. thus be adhered to. In Scotland, where peroxide has been applied extensively since Vaccines 1992, the recommended dosage is 1500 ppm for 20 minutes, depending on water temper- The genetics of L. salmonis is the subject of ature (Treasurer et al. 2000). current research to isolate and produce cloned antigens for vaccines (Spencer 1992). Hydrogen peroxide is believed to kill sea lice The appeal of a vaccine is that it is clean (Treasurer et al. 2000) when gas bubbles relative to chemical therapeutics, vis a vis, cause mechanical paralysis; dead lice float to residues in tissue or other species. the surface where they can be skimmed off. Not all lice are killed, and some recover, No vaccine has yet been developed, but requiring repeated treatments, opening an research in this direction is continuing (e.g., avenue for the development of resistance. Raynard et al. 1995, Anon. 1998) Treasurer et al. (2000) showed that sea lice TREATMENT build resistance over repeated treatments. Once an outbreak has occurred there are Egg bearing female lice that had never been several options available to sea farm opera- exposed to hydrogen peroxide were reduced tors: hydrogen pyroxide, organophosphates by about 90% after initial treatment. Sea lice (e.g., and ), on fish from a farm that had been treated ivermectin, pyrethrins, and . many times were reduced by only 25%. The

22 Salmon Farms, Sea Lice & Wild Salmon growing resistance often prompts increased dichlorvos persists up to three weeks in the treatment frequency and dosages, and collat- liver and brain. If a repeat treatment is eral increases in fish mortality (Treasurer et required—and it is recommended (Johnson al. 2000). 1992)—there may be a risk of increased Hydrogen peroxide has a narrow margin fish mortality (Spencer 1992). between safe and lethal doses to fish. At At too high a concentration of dichlorvos, 2350 ppm for 23 minutes, there is no fish fish also become narcotized, and sink to mortality. Increasing the duration by an the bottom of the net, where they can be additional four minutes increases the mor- suffocated by other narcotized fish (Spencer tality of fish to nine percent (Treasurer et al. 1992). Other side effects include reduced 2000). Thus, there is a large risk that fish growth and increased stress, manifested as are inadvertently overexposed. This risk is secondary outbreaks of disease (Johnson further compounded because it is difficult to 1992). Its apparent risks are becoming an achieve an even distribution of peroxide increasing liability and there is pressure in within the bath treatment. Effectiveness also Europe, where it is widely used, to phase it depends on temperature. Below 10ºC, fish out. are especially sensitive to the chemical Azamethiphos is even more toxic than (Johnson 1992). A peroxide treatment is dichlorvos, and is used as an alternative least effective on adult females (ovigerous once sea lice populations develop resistance females have the lowest mortality rate of all to dichlorvos. At one ppm, 60% of Atlantic the mobile lice stages). Peroxide does have salmon were killed in trials. The recom- one advantage: it is easy to dispose of, since mended dose for sea lice treatment is 0.1 to its breakdown products are oxygen and 0.2 ppm. hydrogen. Trichlorfon, another , has Organophosphates been used in Norway under the trade name Neguvon®. The limitations on other orally This family of compounds inhibits acetyl- administered treatments apply to this cholinesterase, thereby interfering with the chemical, but one of the sub-lethal effects cholinergic nervous system (a neurotoxin). is blindness, which occurs from too high a Various compounds used for sea lice dose (Brandal and Egidius 1977). treatment are dichlorvos, marketed as Aquagard® or Nuvan®; trichlorfon, Ivermectin marketed as Neguvon®; and azamethiphos. Ivermectin is derived from the fungi Strepto- Azamethiphos is the only organophosphate myces avermitilis, and has been widely used approved for use in Canada by Health to combat parasites in farm mammals Canada (Haya et al. 2001). The use of these (Spencer 1992). This chemical has a high chemicals as treatments for sea lice is efficiency and works by inhibiting nerve reviewed in Spencer (1992). pulse transmission at the neuromuscular Organophosphates are effective only against junctions in crustacea. It was widely used in preadult and adult stages, and do not kill Europe by salmon farm operators, long chalimus larvae. They are temperature before it was licensed. It is given orally, dependent, have a narrow therapeutic which while easier to administer than baths, margin, leave residue in fish tissues, and has its own set of problems. Most particular- pose risks to fish (and consumers). The ly, it is difficult to regulate the dosage, since nervous system inhibition caused by it is almost impossible to ensure that fish are

A Watershed Watch Report on Risk, Responsibility and the Public Interest 23 getting similar amounts of feed. This is a target species. Sensitivity to the effects of concern, given a narrow safety margin. dichlorvos has been demonstrated in lobster Another limitation is that it takes up to larvae, the common mussel, and the amphi- three weeks to kill lice. It is also poorly pod Hyale nilsonni (reported in Spencer assimilated in the fish gut, and much is 1992). Haya et al. (2001) studied the effects excreted, with the excrement retaining its of chemical wastes produced by salmon toxic effect (i.e., on the ocean floor; Haya et aquaculture on the marine benthic environ- al. 2001). ment. The authors argue that most of the guidelines for chemicals used to treat infec- Experimental doses fed orally to smolts for tions were developed for land-based use, 19 weeks led to significant reductions in and for levels safe for mammals. Chemicals mobile lice stages, compared to controls. are also being used without sufficient avail- able information on lethal and sub-lethal Pyrethrum effect on marine invertebrates. Tests showed The insecticide pyrethrum is a derivative lethal effects to lobster larvae exposed to from the flowers of a chrysanthemum, azamethiphos, pyrethrins, and cyperme- Chrysanthemum cinerariaefolium. Widely thrin. Ivermectin, in the form of undigested used against parasites in humans and food, was also lethal to sand shrimp. , it has also been used in treating sea Collier and Pinn (1998), investigating the lice (Spencer 1992). It is mixed with paraf- effects of ivermectin on a benthic communi- fin oil that floats on the surface of the water ty, demonstrated that ivermectin accumu- in the net pen, allowing it to be absorbed by lates on the substrate in an active form that the lipid-soluble cuticle of the lice, while has a detrimental effect on the benthic being repelled by the impermeable, mucous community. surface of the fish. The oily layer has a limit- ed period of effectiveness, and the active CLEANER FISH () ingredient, pyrethrum, is oxidized by sun- light; wave action further disperses the layer. In some farms in Europe, three indigenous As long as the pyrethrum coats the water wrasse (cleaner fish) have been tested for surface, salmon infected with sea lice may effectiveness in removing sea lice from jump to the surface, and delouse themselves. salmon (as an alternative to chemicals). Experimental trials have resulted in 43% to Unfortunately, wrasse are not well adapted 80% reduction in the number of adult lice to net pens; they prefer lurking among pro- (reported in Johnson 1992). Resistance to its tective vegetation or outcroppings, require lethal effects has been detected in sea lice acclimatization, and only about one out of (Treasurer et al. 2000). 30 actually eat lice (reported in Johnson 1992). Wrasse also target larger lice, ignor- SECONDARY ENVIRONMENTAL ing the chalimus stage and early preadults. EFFECTS OF THERAPEUTICS Concerns are also being raised in the UK Because the chemical baths are emptied into that the local wrasse populations are being the marine environment, there is concern depleted, as demand for these species that their active ingredients may affect non- increases.

24 Salmon Farms, Sea Lice & Wild Salmon Appendix D: GLOSSARY

Biocide: an agent that destroys life Osmoregulation: the technique by which fish regulate and maintain their internal water Copepod: a major group of small crustaceans; and salt concentrations against those in some are free-swimming, while others are the surrounding environment, i.e., parasitic on the skin and gills of saltwater or freshwater. fishes. Osmoregulatory: ability to control the salt Disease: organisms suffer from disease when and water content of the body their normal function is impaired by some genetic disorder, or more often from the Outbreak: a sudden appearance of disease activity of a parasite or other organism in a population occurring with high living within them. A disease is when prevalence. alteration of the body or one of its organs so disturbs normal physiological function. Parasitic: living and feeding in or on another organism to the detriment of Ectoparasite: external parasite that organism

Enzootic: a disease agent that is native to Phototactic: movement in response to light an area. Postsmolt: a juvenile salmon that has adapted Epidemic: an occurrence of disease that is to saltwater. temporarily of high prevalence. Sea lice: a term that commonly includes Fallowing: leaving a fish farm site empty of several species of parasitic copepods in cultured fish for a specific time. the family Caligidae. Two genera found in BC coastal waters are Caligus and Fecundity: reproductive fertility Lepeoptheirus. The term ‘sea lice’ as used Immuno suppression: to suppress or weaken in this report refers to Lepeophtheirus the immune system salmonis unless otherwise noted.

Intensity: number of parasites infecting an Smolt: a juvenile salmon that has recently individual host. entered the saltwater stage from freshwater. Lymphocyte: a leucocyte (white blood cell) inhabiting both the blood and lymph Transmission: mode of transfer of disease to a new host, typically water borne (e.g., Mortality rate: measure of the frequency of fish to fish) or ingestion of agent or of deaths over a period of time in the total an infected aquatic organism. Vertical population. transmission: from parent to offspring, and lateral transmission: from one Narcotized: use of a narcotic or other drug to member of a population to another. induce sleep or sleepiness

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