Distributions of planktonic sea lice larvae Lepeophtheirus salmonis in the inter-tidal zone in Loch Torridon, Western Scotland in relation to salmon farm production cycles

McKibben, Margaret A; Hay, D. W.

doi:10.1111/j.1365-2109.2004.01096.x

Cited by 79 publications

(59 citation statements)

References 25 publications

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“…This correlation indicates that the gravid L. salmonis on the farmed salmon were an important source of sea louse larvae. Plankton surveys have suggested that larval Lepeophtheirus salmonis can be carried several kilometres landward from their source (McKibben & Hay 2004a, Penston et al 2004, and this suggestion is supported by numerical models (Asplin et al 2004, Murray & Gillibrand 2006, Gillibrand & Willis 2007. This implies that self-sustaining L. salmonis populations on farms (Tully 1989, Bron et al 1993a,b, Jackson et al 1997, Revie et al 2005) might be contributing to infestation pressure in the wider environment, not just in their immediate vicinity.…”

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confidence: 55%

“…However, because the identity of the nauplii is presumptive, we shall refer to the nauplii generically as 'sea louse nauplii'. Previous plankton surveys in Loch Shieldaig also found L. salmonis to be the predominant louse species (McKibben & Hay 2004a, Penston et al 2008. Larval L. salmonis densities were significantly lower for a large part of Cycle 2 compared to Cycle 1.…”

Section: Discussionmentioning

confidence: 95%

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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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confidence: 55%

Section: Discussionmentioning

confidence: 95%

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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“…Experiments in the laboratory and sea pens have shown that L. salmonis copepodites swim upwards towards light and do not cross into low salinity waters (Heuch 1995;Heuch et al 1995;Bricknell et al 2006). Plankton sampling discovered higher densities of L. salmonis copepodites in very shallow water along the seashore and in estuarine areas of Ireland and Scotland (Costelloe et al 1995(Costelloe et al , 1998McKibben & Hay 2004). While the same copepodite distribution may be expected in British Columbia, it requires confirmation because the Pacific and Atlantic populations of L. salmonis are genetically distinct (Tjensvoll et al 2006;Todd et al 2006) and may have different evolutionary adaptations.…”

Section: Research Progress (A) Larval Dispersal and Transportmentioning

confidence: 99%

How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere

2009

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Fishes farmed in sea pens may become infested by parasites from wild fishes and in turn become point sources for parasites. Sea lice, copepods of the family Caligidae, are the best-studied example of this risk. Sea lice are the most significant parasitic pathogen in salmon farming in Europe and the Americas, are estimated to cost the world industry E300 million a year and may also be pathogenic to wild fishes under natural conditions. Epizootics, characteristically dominated by juvenile (copepodite and chalimus) stages, have repeatedly occurred on juvenile wild salmonids in areas where farms have sea lice infestations, but have not been recorded elsewhere. This paper synthesizes the literature, including modelling studies, to provide an understanding of how one species, the salmon louse, Lepeophtheirus salmonis, can infest wild salmonids from farm sources. Three-dimensional hydrographic models predicted the distribution of the planktonic salmon lice larvae best when they accounted for wind-driven surface currents and larval behaviour. Caligus species can also cause problems on farms and transfer from farms to wild fishes, and this genus is cosmopolitan. Sea lice thus threaten finfish farming worldwide, but with the possible exception of L. salmonis, their host relationships and transmission adaptations are unknown. The increasing evidence that lice from farms can be a significant cause of mortality on nearby wild fish populations provides an additional challenge to controlling lice on the farms and also raises conservation, economic and political issues about how to balance aquaculture and fisheries resource management.

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“…Temporal patterns in the abundance of planktonic L. salmonis nauplii and copepodids in coastal and off-shore regions of a Scottish loch are correlated with treatment or relocation actions of farmed salmon within the same loch (McKibben & Hay 2004, Penston et al 2008, Penston & Davies 2009. Similarly, infection pressure on sentinel salmon smolts is related to the abundance of ovigerous L. salmonis on adjacent populations of cultured salmon (Bjørn et al 2011, Pert et al 2014.…”

Section: Mitigating Factors and Spillbackmentioning

confidence: 99%

Disease management mitigates risk of pathogen transmission from maricultured salmonids

Jones¹,

Bruno²,

Madsen³

et al. 2015

Aquacult. Environ. Interact.

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Open marine net pens facilitate virus and sea lice transfer, occasionally leading to infections and outbreaks of disease in farmed salmon. A review of 3 salmon pathogens (infectious salmon anaemia virus [ISAV], salmon alphavirus [SAV] and the salmon louse Lepeophtheirus salmonis) shows that increased risk of exposure to neighbouring farms is inversely related to distance from and directly related to biomass at the source of infection. Epidemiological techniques integrating data from oceanography, diagnostics and pathogen shedding rates and viability contribute to improved understanding of pathogen transmission pathways among farms and permit the designation of areas of risk associated with sources of infection. Occupation of an area of risk may increase the likelihood of exposure, infection and disease among susceptible fish. Disease mitigation in mariculture occurs at 2 scales: area-based (coordinated stocking, harvesting and fallowing) and farm-based (vaccination, early pathogen detection, veterinary prescribed treatments and depopulation or early harvest in the event of viral disease). Collectively, implementation of mitigation measures results in virus disease outbreaks of shorter duration with lower mortality and therefore reduces the likelihood of pathogen transmission. In contrast, the mitigation of sea lice transmission is less likely to be effective in some areas due to the loss of parasite sensitivity to therapeutants and to dissemination of larval lice when parasites occur below management thresholds. For wild populations, risk of pathogen spillback is estimated from farm-based epidemiological data; however, validation, particularly for ISAV and SAV, is required using direct surveillance.

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Distributions of planktonic sea lice larvae Lepeophtheirus salmonis in the inter-tidal zone in Loch Torridon, Western Scotland in relation to salmon farm production cycles

Cited by 79 publications

References 25 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

How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere

Disease management mitigates risk of pathogen transmission from maricultured salmonids

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