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1.
The efficacy of emamectin benzoate (SLICE) against sea lice infestations of Atlantic salmon, Salmo salar L., is typically assessed using untreated fish, or fish treated with alternative therapeutants, as controls. The State of Maine, USA, is currently under active management for the OIE-notifiable pathogen, infectious salmon anaemia virus (ISAV); consequently, neither control group is feasible in this region. Untreated salmon risk extensive damage from the ectoparasites, and threaten to increase vector-borne exposure or susceptibility of farms to ISAV; and the only treatment presently available in Maine is SLICE. However, because sea lice infestations are unlikely to resolve spontaneously, and response to treatment occurs within weeks, use of a pretreatment baseline is a reasonable alternative for confirmatory studies. We evaluated SLICE efficacy on Atlantic salmon farms in Cobscook Bay 2002-2005, in the absence of untreated controls, using pretreatment lice loads as a reference for calculation. Maximum efficacy ranged from 68% to 100% reduction from initial levels. Time-to-maximum efficacy ranged from 1 to 8 weeks after treatment initiation. Efficacy duration, measured between first reduction and first progressive rise in counts, ranged from 4 to 16 weeks.  相似文献   

2.
A monitoring program for the prevalence and intensity of sea lice infestations of wild and escaped farmed salmon has been underway on the Magaguadavic River since 1992. Fish are screened in a fish ladder trap located in freshwater a short distance above the head of tide. No trends with time were evident in observed sea lice burdens, and in all years the majority of salmon, both wild and escapees, had no or low levels of infestation with sea lice. In the spring of 2002, 23 landlocked salmon moving to sea from the Magaguadavic River were acoustically tagged. Two fish returned to the river after a brief period of residence in Passamaquoddy Bay, with significant dermal damage from sea lice. These fish were tracked to areas close to commercial salmon farms.  相似文献   

3.
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4.
The relationship between aquaculture and infestations of sea lice on sea trout, Salmo trutta L., is controversial. Here, the association between sea lice infestations on wild sea trout and characteristics of local Atlantic salmon, Salmo salar L., farms were investigated using data collected on the Scottish west coast. The proportion of sea trout with louse burdens above a critical level was positively related to the fork length of the sea trout and the mean weight of salmon on the nearest fish farm, and negatively related to the distance to that farm. The distance to the nearest fish farm did not influence the probability of infestations above the critical level beyond 31 km although there was considerable uncertainty around this cut‐off distance (95% limits: 13–149 km). The results support a link between Atlantic salmon farms and sea lice burdens on sea trout in the west of Scotland and provide the type of information required for marine spatial planning.  相似文献   

5.
We examine sea lice, Lepeophtheirus salmonis , on juvenile and adult salmon from the north coast of British Columbia between 2004 and 2006 in an area that does not at present contain salmon farms. There is a pronounced zonation in the abundance of L. salmonis on juvenile pink salmon, Oncorhynchus gorbuscha , in the Skeena and Nass estuaries. Abundances in the proximal and distal zones of these estuaries are 0.01 and 0.05 respectively. The outer zones serve as feeding and staging areas for the pink salmon smolts. Returning Chinook, Oncorhynchus tshawytscha , and coho salmon, Oncorhynchus kisutch , concentrate in these areas. We collected data in 2006 to examine whether L. salmonis on returning adult salmon are an important source of the sea lice that appear on juvenile pink salmon. Nearly all (99%) of the sea lice on returning Chinook and over 80% on coho salmon were L. salmonis. Most of the L. salmonis were motile stages including many ovigerous females. There was a sharp increase in the abundance of sea lice on juvenile pink salmon smolts between May and July 2006 near the sites of adult captures. As there are no salmon farms on the north coast, few sticklebacks, Gasterosteus aculeatus , and very few resident salmonids until later in the summer, it seems that the most important reservoir of L. salmonis under natural conditions is returning adult salmon. This natural source of sea lice results in levels of abundance that are one or two orders of magnitude lower than those observed on juvenile pink salmon in areas with salmon farms such as the Broughton Archipelago.  相似文献   

6.
Sea lice are a persistent problem for farmed and wild salmonid populations. Control can be achieved through the use of veterinary medicines. A model was developed to describe the patterns of sea lice infection on salmon farms in Scotland and to predict the likely effect of various treatment strategies. This model takes into account development rates and mortality using compartments representing life history stages and external infection pressure. The national sea lice infection pattern was described using parameters representing stage survival, background infection levels and egg viability rates. The patterns observed across farms varied greatly and the model gave broad agreement to observed trends with different parameters being required in the model for sites using hydrogen peroxide and cypermethrin treatments. The parameter estimates suggest that the background infection pressure on sites where cypermethrin was administered was higher than for those using hydrogen peroxide. Both models had comparable magnitudes of sensitivity with survival from one stage to another being the most sensitive parameter, followed by feedback rates at which gravid females produce eggs, with background infection levels the least sensitive. The effect of different cypermethrin treatment strategies was assessed using the model. Increasing treatments in a production cycle gave more effective control. However, the model showed that timing of treatments is most important if sea lice are to be effectively controlled.  相似文献   

7.
Salmon farming began in British Columbia (BC) in the 1970s and in 2006, aquaculture represented BC's largest agricultural export. Along with this growth in production has been a growth in controversy, including the concern that sea lice originating from Atlantic salmon farms negatively impact wild juvenile pink salmon in the Broughton Archipelago. To understand the dynamic interaction between wild and farmed fish, data for on‐farm abundance of sea lice are required. In this study, 33 000 Atlantic salmon from 20 active farms were examined over 3 years. Two species of lice were found: Lepeophtheirus salmonis and Caligus clemensi. Inter‐annual and seasonal variations in abundance levels occurred with lower levels of L. salmonis in 2003 compared with 2004 and 2005, while C. clemensi levels were highest in 2003. The abundance of L. salmonis was greater on older farmed fish. The findings are compared with European and eastern Canadian sea lice reports, and possible sources of sea lice on farmed salmon are discussed.  相似文献   

8.
This study examines the relative density of sea lice, Lepeophtheirus salmonis (Krøyer), larvae in the inter‐tidal areas of Loch Torridon, a fjordic sea loch in Western Scotland and the site of several commercial salmon farms. Samples of planktonic sea lice were collected in each spring from 1999 to 2003 near the mouth of the River Shieldaig, where sea trout have been shown to congregate in the first few days after going to sea, and from 2001 to 2003 near the mouth of the River Balgy. No larval sea lice were found near the mouth of the River Shieldaig in spring 2000 or 2002, when gravid female sea lice were absent on local fish farms. The same finding was observed in 2002 at the mouth of the River Balgy. In springs of 1999, 2001 and 2003, peak densities of larval sea lice of 33, 94 and 143 m?3, respectively, were observed at the mouth of the river Shieldaig. At the mouth of the River Balgy, peak densities of 74 and 78 lice m?3 were observed in 2001 and 2003 respectively. At the time these samples were collected, the two local salmon farms were in the second year of their production cycle and gravid female sea lice were present. Samples of larval sea lice were also obtained year round, at approximately weekly intervals, from a 50‐m transect at the mouth of the River Shieldaig, from March 2001 to June 2003, and compared with frequencies of gravid female sea lice on the two local salmon farms. High levels were found in the winter. No planktonic sea lice were found in this transect when gravid females were not present on the local fish farms.  相似文献   

9.
Sea trout (Salmo trutta L.) stocks on the West Coast of Scotland and Ireland have decreased due to reduced survival during the marine phase of their life cycle. Lice‐infested sea trout returning to rivers could indicate that parasite burdens are contributing to the decline. Salmon farms represent a potential source of substantial quantities of sea lice, leading to a conjectured link between parasites on salmon fish farms and infestations on wild sea trout. To investigate the potential infective pressure on sea trout in Loch Shieldaig, offshore and sub‐littoral plankton samples were collected and analysed for sea lice nauplius and copepodid stages. During the plankton survey, numbers of sea lice on a fish farm in the loch reached a maximum in November 2001. Soon after, numbers of sea lice larvae peaked in open‐water samples and then in sub‐littoral samples. Nauplii were found adjacent to the farm and occurred less elsewhere. This study reports a concentration of sea lice larvae at the head of Loch Shieldaig and indicates a possible relationship between sea lice numbers on the fish farm and lice larvae densities in the open‐water of the loch and in the sub‐littoral zone.  相似文献   

10.
ABSTRACT

This article describes the sea lice control methods that are currently applicable to salmon farming in Canada. Three commercial chemical products are approved for use against sea lice in Canada: Slice®, Interox® Paramove® 50, and Calicide®. Physical control methods include photoperiod and cage-depth manipulations, desiccation of farm equipment, and the use of electric fences. Biological control measures include the polyculture of salmon with wrasse or mussel. Nutraceuticals and immunostimulants shown to reduce sea lice infestations in salmon include unmethylated DNA, yeast fermentation extract-Brewer’s yeast compound, AllBrew and NuPro, MacroGard®, and Optimûn®. Salmon farmers are recommended to use site-specific integrated approaches, by properly adapting a combination of chemical, physical, biological, and nutritional measures to the environmental and financial characteristics of their farm. In the future, development of vaccines against sea lice and of salmon lines resistant to sea lice will play a pivotal role in fighting against this parasite.  相似文献   

11.
Analyses of a unique database containing sea lice records over an 11 year period provide evidence of changing infestation patterns in Scotland. The data, collected from more than 50 commercial Atlantic salmon farms, indicate that both species of sea lice commonly found in Scotland, Lepeophtheirus salmonis and Caligus elongatus, have declined on farms over the past decade. Reductions for both species have been particularly marked since 2001 when more effective veterinary medicines became available. Treatment data were also available in the database and these show a growing trend towards the use of the in-feed medication emamectin benzoate (Slice), particularly in the first year of the salmon production cycle. However, this trend towards single product use has not been sustained in 2006, the latest year for which data are available. There is some evidence of region to region variation within Scotland with the Western Isles experiencing higher levels of infestation. However, compared to the levels observed between 1996 and 2000, all regions have benefited from reduced lice infestation, with the overall pattern showing a particular reduction in the second and third quarters of the second year of production.  相似文献   

12.
A plankton survey investigated spatial and temporal distributions of larval sea lice in a sea loch on the north-west coast of Scotland. Plankton tows were collected approximately weekly at two depths (0 and 5 m) at five sample stations over a 2-year period. The survey began in March 2002 when Atlantic salmon, Salmo salar L., farms in the study area stocked with fish and finished in March 2004, after farms completed harvesting. Over 90% of lice recovered were Lepeophtheirus salmonis (Kr?yer); therefore, the results of this paper refer largely to that species. The data were analysed using generalized additive models with explanatory variables for time, depth and station. Greatest densities of nauplii were recovered at stations adjacent to farms indicating that the local salmon farms were a likely source of larvae at times during the production cycle. There were significant temporal trends in larval densities and the stocking and harvesting of farms can possibly account for these increases and decreases, particularly at the start and at the end of the production cycle. The distribution of copepodids was more widespread than that of nauplii, indicating that the larvae can be transported several kilometres from the point of release.  相似文献   

13.
Sea lice data collected from Atlantic salmon farms in the Broughton Archipelago between 2003 and 2005 were examined for inter-regional differences in mobile Lepeophtheirus salmonis (Krøyer) abundance using the generalized linear model procedure. Factors such as age of the salmon populations, location of farms and time of year had a significant effect on the abundance of the mobile stages of L. salmonis whereas water temperature and salinity did not. Separate evaluation of SLICE® treatment data found no significant difference in treatment frequency among the areas but did show that there were significantly lower numbers of farm treatments during the summer months when compared with other seasons. The role of environment and wild fish in influencing sea lice abundance on the farmed salmon is discussed. The findings suggest that effective management programmes for sea lice should not only be based on geographical location but should take into account other factors which could influence lice abundance levels.  相似文献   

14.
Although Caligus elongatus is one of two major species of sea lice that parasitize farmed salmon, its epidemiology has not been extensively studied. In this communication, the abundances of the adult stage of C. elongatus in salmon populations from 33 farms in the West of Scotland between 1997 and 2000 have been analysed for evidence of seasonal and annual patterns. The findings indicate that the pattern of C. elongatus is remarkably consistent from year to year, and directly opposed to that reported for Lepeophtheirus salmonis, the other major caligid species. In particular, adult infestations rapidly increase from the start of July each year, and are more prevalent on salmon in the first year of production than the second year. Treatment is seen to have an effect on levels of infestation but it is not clear why this species should have significantly lower levels of abundance in the second year of production. There is also evidence that fallowing has no effect on abundance. Strategic management programmes for the control of sea lice on salmon farms, which are increasingly effective in controlling L. salmonis , may also have to give greater consideration to C. elongatus .  相似文献   

15.
Sea lice, Caligus rogercresseyi, are ectoparasitic copepods, which severely affect the salmon farming industry in southern Chile, reducing the health status of fish and producing both direct and indirect economic losses. Local farmers have reported increasing infestation levels since 2004, reaching a peak in 2007. In response to this situation, the Chilean Fisheries Service (Sernapesca) developed a surveillance programme; the first step of which consisted of a general survey of salmon farms. This survey included documenting counts of parasite burdens on fish and measurements of several husbandry and environmental factors providing an evaluation of risk factors for the observed infestation levels. The information collected was analysed using a linear mixed model technique, which takes into account the clustered structure of data, decomposing the unexplained variation and assigning it to different aggregation levels of the productive system. Geographical zones, fish species, treatment against sea lice performed 1 month before sampling, stocking density, fish weight and water salinity were the variables significantly associated with sea lice burdens. In contrast, treatments performed 2-3 months before sampling, use of photoperiod in sea cages and water temperature, were not significant. There was significant unexplained variation at all aggregation levels, i.e. sub-zone, fish farm and cage level, with the fish farm level showing the greatest variation.  相似文献   

16.
Epidemiological investigations into the pancreas disease (PD) of farmed salmon were conducted on populations of Atlantic salmon reared in Ireland during 2003 and 2004. The investigations surveyed all marine salmon farms operating in Ireland through a detailed questionnaire with follow-up farm visits. Information was gathered on 21 populations of fish in 2003 and 14 populations in 2004. Thirteen of the 21 populations suffered PD in 2003 and 12 of the 14 in 2004. The mean mortality due to PD on affected farms was 18.8% in 2003 and 14.8% in 2004 and the loss of growth due to PD was estimated at 11.4% over the 2-year period. The highest risk periods for outbreaks of PD were early summer and early autumn and the farms most seriously affected by PD mortality were in the western counties of Ireland. Factors which showed an indication of association with a PD outbreak or high mortality during a PD outbreak were: livestock movement to another sea site, high feeding rate prior to any PD outbreak, the presence of another PD positive farm in the same water body, greater than 250000 fish on a site, a previous history of PD on a site, a high sea lice burden, and sites located in the western regions of Ireland which reared a specific strain of salmon.  相似文献   

17.
Health diets for Atlantic salmon have become an important component of the integrated pest management strategies targeting sea lice. A challenge trial was performed to examine the effect of supplementing salmon diets with either immunostimulants or essential oils. One control and four experimental diets containing immunostimulants or natural identical extracts were fed to Atlantic salmon in triplicate tanks for 4 weeks before challenging the fish with the sea lice copepodids. Prevalence of infection was 100%, and the mean abundance of infection was 21.2. The lowest mean lice count of 17 per fish (P < 0.05) was found in the group fed a mix of natural identical plant extracts (PX I). This represents a 20% reduction in infection, showing the potential for health diets to be employed as a tool to help control sea lice. To gain an understanding of the mechanisms of action underlying this protection, fish fed the control diet and fish fed the PX I diet were compared using quantitative histology of the epidermis and proteomic analysis of epidermal mucus. No significant differences were seen in the thickness of the epidermis or mucous cell percentage area, but differences in expression were seen for a number of proteins, including heat shock proteins, in epidermal mucus.  相似文献   

18.
The efficacy of teflubenzuron (Calicide®) for the treatment of farmed Atlantic salmon (Salmo salar L.) infested with sea lice [Lepeophtheirus salmonis (Krøyer)] was investigated on two commercial salmon farms. Teflubenzuron (Calicide®) coated onto commercial feed pellets was administered orally at 10 mg per kg body weight per day for seven consecutive days. Fish were randomly sampled and lice numbers recorded from both treated and control groups on four sampling occasions post‐medication. Statistically significant reductions in the number of L. salmonis per fish were recorded. Maximum efficacy was observed toward chalimus and preadult stages of L. salmonis, and was achieved about 7 days post‐medication. No apparent effect was observed on adult lice. No adverse drug reactions or palatability problems were associated with the treatments.  相似文献   

19.
The sea louse, Lepeophtheirus salmonis , is an ectoparasitic copepod of Atlantic salmon, Salmo salar L., capable of causing severe damage. This study was conducted to examine the physiological response of salmon to the stress of sea lice infestation. Smoltified salmon were acclimatized in 30‰ saltwater and exposed to high levels of lice infestation. The number of copepods per fish ranged from 15 to 285, with a mean of 106. The infested salmon were sampled six times over the 29-d experimental duration and examined for alterations in the primary and secondary stress indicators, including plasma concentrations of cortisol, glucose, electrolytes, thyroid hormones T3 and T4, as well as the haematocrit level. The results were examined for correlations between the stress indicators, the number of copepods per fish and the life stage of the copepods. The presence of L. salmonis elevated stress indicators in relation to the specific sea lice stage. By day 21, both cortisol (mean 63.1 nmol L−1 controls: 179.8 nmol L−1 for parasitized) and glucose (mean 3.545 mmol L−1 controls: 4.567 mmol L−1 for parasitized) levels were significantly increased due to the presence of the lice. This was believed to be a direct result of the sea lice development into the larger life stages, thus increasing the level of host damage.  相似文献   

20.
Abstract. Developments in the use of wrasse as cleaner-fish in the control of sea lice ( Lepeophtheirus salmonis, Caligus elongatus ) in Ireland are reviewed. Corkwing, Symphodus melops , and goldsinny, Ctenolabrus rupestris , have controlled L. salmonis (<1 louse per salmon) on commercial farms. C. rupestris and rockcook, Centrolabrus exoletus , removed both adult and chalimus C. elongatus in aquarium trials. No egg-bearing lice were ever found on salmon in cages with wrasse, and numbers of mobile lice were maintained at <1 per salmon smolt.
Wrasse are fished using shrimp pots, optimally set for about 2 h. The fishery is seasonal and limited to >10cm wrasse occurring close to the farm, and distant from other farms. Localized reductions in the body length and numbers of wrasse have been detected in the second year of fishing in two areas respectively. Due to the fishery limitations and high fecundity of wrasse, impacts on wrasse populations should remain localized. All wrasse populations fished are screened for microbial diseases, and protozoan and metazoan parasites. Results are typical for wild marine fish but metazoan skin parasites are rare. No pathogens, including tests with an Aeromonas sp. found in wrasse, have been found to be transferable to salmon.
Wrasse are the only effective and continuous method of sea lice control legally available. Research efforts should be directed towards improving the availability, pathogen-free status, and husbandry of wrasse, to enable cleaner-fish technology to be more widely and efficiently utilized.  相似文献   

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