Variations in parasitic caligid infestations on farmed salmonids and implications for their management

Jackson, David W.; Deady, Sandra; Leahy, Yvonne; Hassett, Daniel J.

doi:10.1016/s1054-3139(97)80015-x

Cited by 25 publications

(31 citation statements)

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Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…Fallowing can break the life cycle of L. salmonis populations at farms by removing the host for a period greater than the lifespan of the larval stages, ca. 30 d (Grant & Treasurer 1993, Jackson et al 1997.Initial infestations of Lepeophtheirus salmonis on farmed salmon most likely result from larvae released by gravid L. salmonis on wild sources (Bron et al 1993b, Pike & Wadsworth 1999, Revie et al 2002. However, once an L. salmonis population has become established at a farm, the majority of further larvae infesting that farm will have originated from the L. salmonis on farmed fish (Tully 1989, Bron et al 1993a,b, Revie et al 2005.…”

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Reduced Lepeophtheirus salmonis larval abundance in a sea loch on the west coast of Scotland between 2002 and 2006

Penston¹,

Millar²,

Davies³

2008

Dis. Aquat. Org.

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A survey for planktonic sea louse larvae was carried out in Loch Shieldaig, Scotland, between 2002 and2006, and spanned 2 successive production cycles (Cycles 1 and 2) at a local Atlantic salmon Salmo salar L. farm. The vast majority of the caligid copepodids recovered were Lepeophtheirus salmonis; however, the methodology was unable to determine the species of the caligid nauplii. Greatest densities of nauplii were found at the sampling station adjacent to the salmon farm, and larval densities were low during the fallow period of both cycles. Peaks in nauplius densities occurred around the same time in the 2 cycles, but the peaks were significantly lower during Cycle 2 than Cycle 1. Lepeophtheirus salmonis copepodid densities varied temporally, but not spatially. During most of Cycle 2, copepodid densities were significantly lower than those recovered during Cycle 1. Numbers of gravid L. salmonis at the local salmon farm correlated significantly with densities of louse nauplii and L. salmonis copepodids in the water at time lags of 0 and 1 wk, and 1 and 2 wk, respectively. This survey demonstrated a reduction in densities of L. salmonis larvae in the plankton (an indication of L. salmonis infectious pressure) between the 2 cycles and indicated that the farm was an important source of L. salmonis larvae. The application of anti-louse treatments using emamectin benzoate reduced the numbers of gravid L. salmonis at the farm, and this was the main factor influencing the apparent reduction in L. salmonis infectious pressure in the loch between cycles. KEY WORDS: Lepeophtheirus salmonis · Sea lice · Larvae · Salmon farm · Scotland Resale or republication not permitted without written consent of the publisherDis Aquat Org 81: [109][110][111][112][113][114][115][116][117] 2008 duration of each stage of development is strongly dependent on temperature (Johnson & Albright 1991a). Under average sea surface temperatures in Loch Torridon (around 10°C), L. salmonis nauplii and copepodids would last approximately 3 and 8 d, respectively (Johnson & Albright 1991a), but may become less capable of finding a host after just a few days as finite energy reserves dwindle (Tucker et al. 2000).Few published accounts have described the behaviour of Lepeophtheirus salmonis larvae in the wild. Costelloe et al. (1998a,b) frequently recovered L. salmonis larvae near salmon farms in Ireland. They suggested that most of these larvae were probably of farm origin and that intermittent pulses of L. salmonis larvae that occurred near river mouths were probably of wild origin. A study in Loch Shieldaig, Scotland (Penston et al. 2008), suggested that the majority of louse larvae recovered near a salmon farm were the progeny of L. salmonis on farmed salmon. In contrast to Costelloe et al. (1998a,b), who concluded that farms only influence L. salmonis populations in their immediate environs, Penston et al. (2008) suggested that L. salmonis larvae can have a widespread effect in the surrounding waters.As with most salmon farms in Scotl...

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Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

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confidence: 99%

Reduced Lepeophtheirus salmonis larval abundance in a sea loch on the west coast of Scotland between 2002 and 2006

Penston¹,

Millar²,

Davies³

2008

Dis. Aquat. Org.

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“…Significant geographic variability has been reported in the infestations of sea lice among cultured salmon populations of several countries (Jaworski & Holm 1992, Hogans 1995, Boxaspen 1997, Jackson et al 1997. However, none of these studies adjusted their results by the effect of different management and environmental factors, and hence the spatial effect reported might have been confounded by such factors (i.e.…”

Section: Random Effectsmentioning

confidence: 99%

“…No studies have described the effects of different environmental and management factors that may influence sea lice burdens on salmonids cultured in southern Chile. Univariate analyses of such environmental and management factors are common in the literature for salmonids cultured in northern hemisphere countries (Jaworski & Holm 1992, Hogans 1995, Boxaspen 1997, Jackson et al 1997, Rivie et al 2002. However, these reports ignore the nested structure of the data sets from salmon farms, i.e.…”

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confidence: 99%

Spatial and temporal variations in sea lice (Copepoda: Caligidae) infestations of three salmonid species farmed in net pens in southern Chile

Zagmutt-Vergara¹,

Carpenter²,

Farver³

et al. 2005

Dis. Aquat. Org.

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Sea lice infestations have become a major health problem for farmed salmonids throughout the world including Chile. In southern Chile, 6 geographical areas, divided into 22 geographical zones with a total of 127 salmon farming centers and 1519 sea pens, were regularly sampled from December 1999 to April 2002. A linear mixed-effects model (LME) approach was used to describe the infestations of adult forms of sea lice on 3 salmonid species farmed in southern Chile. The variables fish species, water temperature, water salinity, fish weight, juvenile parasite count, pen shape, treatment status in previous month and the interaction of previous and current month treatments were found to be statistically significant fixed effects for the population sampled. The most susceptible species to sea lice infestation was rainbow trout Oncorhynchus mykiss, while the least susceptible species was coho salmon O. kisutch. Fishes in pens treated in the previous month with avermectins were associated with the smallest sea lice count compared to fishes in pens not treated or treated with other products. The variability in sea lice infestations in areas and zones within areas was not statistically significant when controlling for the previously mentioned fixed variables. The variability between centers, the within-pen variability, and the interaction between within-pen effect and the date of measurement were statistically significant and not explained by the fixed effects. Potential sources for this variability are discussed. We conclude that the epidemiology of sea lice infestations in farmed salmonids in southern Chile is complex and in need of further study. KEY WORDS: Sea lice · Epidemiology · Fish health · Farmed salmonids · Linear mixed modelsResale or republication not permitted without written consent of the publisher

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“…Differential susceptibility to L. salmonis occurs among salmon species. On salmon farms in Ireland, rainbow trout (Oncorhynchus mykiss) carried fewer L. salmonis than did Atlantic salmon [9] and in Japan, fewer L. salmonis occurred on coho salmon (Oncorhynchus kisutch) compared with rainbow trout, despite concurrent exposures to the parasite from wild chum salmon (Oncorhynchus keta) [10]. While the mean abundance of lice declined both on sea trout (Salmo trutta) and Atlantic salmon, a higher mean abundance was maintained on the sea trout eight weeks following a laboratory exposure, suggesting greater susceptibility [11].…”

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Defence against the Dark Arts: Mechanisms of Resistance among Salmon to the Parasitic Copepod Lepeophtheirus salmonis

Jones¹

2013

J Aquac Res Development

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IntroductionCopepods belonging to the family Caligidae, referred to as sea lice, are ectoparasites of marine fishes. All sea lice share similar life cycles including nauplius stages and an infective copepodid stage that disperse in the plankton while subsisting on endogenous lipids. Once settled onto a suitable host, the copepodid moults through four chalimus stages that are tethered to the host with a frontal filament. Depending on species, the parasite further develops through one or two preadult stages to the adult stage which are untethered and mobile on the host. Much of the damage caused by parasitic copepods is related to attachment to the host ( Figure 1) and feeding behaviour: the parasites graze on host tissues that range from mucus, cells of the epidermis, dermis or subcutaneous tissues. The more invasive feeding behaviours are associated with the larger developmental stages.Species of sea lice parasitic on salmonid fishes are well described pests in marine aquaculture and in the northern hemisphere include Lepeophtheirus salmonis (the salmon louse) and several species of Caligus [1][2][3][4]. Infections with L. salmonis incur annual costs to marine open netpen aquaculture in excess of 700M Euros in Norway, Scotland, Ireland and Canada [5]. In addition, infections with Caligus rogercresseyii are a significant economic burden to salmon aquaculture in Chile [6]. Management of sea lice infections in aquaculture depends on integrated husbandry schemes including chemotherapeutant intervention [7]. However, recent trends indicate a declining efficacy for many compounds used for treatment, suggesting that in several jurisdictions L. salmonis or C. rogercresseyii have developed tolerance or resistance to these compounds. The absence of commercially efficacious vaccines against sea lice reflects a lack of detailed knowledge of immunogenic parasite antigens that elicit protective immunity in salmonids. In addition, defence responses against parasitic copepods in fishes are poorly documented. A more thorough understanding of teleost defense mechanisms against sea lice will provide a rational basis for the development of novel management strategies. The purpose of this paper is to review the current understanding of salmonid defence responses to L. salmonis. AbstractThe purpose of this paper is to review the current knowledge of salmonid defence responses to Lepeophtheirus salmonis. The salmon louse L. salmonis is an important pest of economically valuable salmonids in seawater throughout the northern hemisphere. Treatment of salmon lice on cultured salmon often fails in regions where the parasite has developed resistance to commonly used therapeutants. The development of efficacious vaccines is hampered by limited knowledge of parasite antigens that elicit protective immunity and a poor understanding of defence responses mounted by the salmonid host. Infection kinetics indicate a wide range of susceptibilities to L. salmonis among salmon species: juvenile coho and pink salmon are relatively resistant whereas Atl...

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Variations in parasitic caligid infestations on farmed salmonids and implications for their management

Cited by 25 publications

References 3 publications

Reduced Lepeophtheirus salmonis larval abundance in a sea loch on the west coast of Scotland between 2002 and 2006

Reduced Lepeophtheirus salmonis larval abundance in a sea loch on the west coast of Scotland between 2002 and 2006

Spatial and temporal variations in sea lice (Copepoda: Caligidae) infestations of three salmonid species farmed in net pens in southern Chile

Defence against the Dark Arts: Mechanisms of Resistance among Salmon to the Parasitic Copepod Lepeophtheirus salmonis

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