Planktonic Distribution of Sea Lice Larvae, <i>Lepeophtheirus Salmonis</i>, in Killary Harbour, West Coast of Ireland

Costelloe, M.; Costelloe, Justin F.; O'donohoe, G.; Coghlan, N. J.; Oonk, M.; Heijden, Y Van Der

doi:10.1017/s0025315400044830

Cited by 50 publications

(52 citation statements)

References 20 publications

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“…If, as this study and others suggest (Costelloe et al 1996, 1998a,b, Penston et al 2004, the majority of the sea louse nauplii recovered near fish farms (e.g. Stn C) are derived directly from Lepeophtheirus salmonis on farmed salmon, then L. salmonis control measures applied at the farm, such as fallow periods and treatments, would be expected to affect larval densities, particularly nauplius densities.…”

Section: Discussionmentioning

confidence: 58%

“…Costelloe et al (1996) postulated that larvae released from lice on farmed salmon would have little effect on louse infestations outside the immediate environs of the farm. However, despite the possibility that some L. salmonis copepodids recovered in Loch Shieldaig might have been transported there from elsewhere, the bulk of the louse larvae would be expected to have been generated locally, as the largest farm in the area is located in this loch, and it is unlikely that L. salmonis larvae from sources other than the gravid L. salmonis on farmed salmon at Farm 1 would improve the correlation between recovered larval densities, particularly nauplius densities, and counts of gravid L. salmonis at Farm 1.If, as this study and others suggest (Costelloe et al 1996, 1998a,b, Penston et al 2004, the majority of the sea louse nauplii recovered near fish farms (e.g. Stn C) are derived directly from Lepeophtheirus salmonis on farmed salmon, then L. salmonis control measures applied at the farm, such as fallow periods and treatments, would be expected to affect larval densities, particularly nauplius densities.…”

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confidence: 69%

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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: Discussionmentioning

confidence: 58%

mentioning

confidence: 69%

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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“…The project coincided with a period of unusually high rainfall (approximately 2200 mm in 2011; SEPA Lingerton data), compared to an average of 1750 mm (Edwards & Sharples 1986); regional averages have remained fairly stable over the last 25 yr (Met Office data not shown). It is thought that adult sea lice can-not survive long periods in freshwater (McLean et al 1990), and previous studies have found lice to be absent from surface waters during periods of heavy rainfall (Costelloe et al 1998), leading to the idea that they might migrate vertically to avoid this influx of freshwater. Particle-tracking simulations were run using identical forcing, but with particles assumed to inhabit layers 2 (mean depth 4.98 m) and 3 (mean depth 8.3 m; mean depth in layer 1 is 1.66 m), to determine whether vertical migration of larvae influenced dispersal patterns.…”

Section: Scenariosmentioning

confidence: 99%

Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland

Adams¹,

Black²,

MacIntyre³

et al. 2012

Aquacult. Environ. Interact.

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Sea lice are a persistent threat in many areas where salmon farming is practised. In common with the management of disease, infection levels are typically controlled by operating sites within distinct geographical areas, allowing for coordinated treatment and fallow cycles. However, the hydrodynamic connectivity and consequent transmission of lice larvae between sites is often not well understood, which limits our ability to optimise the spatial distribution of farms to minimise infection. We used a multistage modelling approach to investigate the transmission of sea lice larvae between salmon aquaculture sites in Loch Fyne, Scotland. A finite element hydrodynamic model was forced using meteorological data collected over the study period. Output from this model was used to drive a particle-tracking model. The latter model implemented the development and mortality of larvae to estimate the probability of successful larval dispersal between sites. In turn, these dispersal probabilities were used to define a network describing the sea lice metapopulation (its habitat defined by the aquaculture sites). Methods from graph theory allow the identification of those sites in the network that are likely to be key for the control of sea lice in the loch population as a whole. Model outputs were compared with data from a campaign of plankton tows and with lice abundance data from aquaculture sites. The general pattern of abundance was reasonably well replicated, albeit with some notable discrepancies. These differences are worth investigating further, as they may be suggestive of sources of infection by wild fish or of inadequacies in the model.

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“…Lepeophtheirus salmonis copepodids are stenohaline, suggesting their activity and survival would be severely compromised in waters of reduced salinity (Pike & Wadsworth 2000). Sporadic abundance around river mouths was negatively correlated with rainfall, suggesting that a decrease in salinity through increased rainfall reduces copepodid abundance (Costello et al 1998b). Heuch (1995) reported that Lepeophtheirus salmonis copepodids maintained in a linear salinity gradient aggregated in salinities of 19 to 24 parts per thousand (ppt) during light conditions, and in salinities as low as 15 to 17.2 ppt in darkness, despite having the option of high saline conditions.…”

Section: Introductionmentioning

confidence: 99%

Effect of environmental salinity on sea lice Lepeophtheirus salmonis settlement success

Bricknell¹,

Dalesman²,

O'Shea³

et al. 2006

Dis. Aquat. Org.

166

162

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The sea louse Lepeophtheirus salmonis (Krøyer, 1837) (Copepoda: Caligidae) is an ectoparasite of salmonid fish. It has earlier been proposed that the free-swimming infectious copepodid stage of L. salmonis gather at river mouths to infect wild Atlantic salmon Salmo salar L. and sea trout S. trutta L. smolts during their seaward migration. This study used aquarium-based methods to investigate the survival, infective ability and behaviour of L. salmonis copepodids exposed to short periods of low salinity levels, such as those encountered at river mouths. Survival of free-swimming copepodids was found to be severely compromised at salinity levels below 29 parts per thousand (ppt). Attachment to an S. salar host did not aid copepodid survival during post-infection exposure to low salinity environment, and a reduction in salinity appears to reduce the ability of copepodids to remain attached to S. salar smolts. Pre-infection exposure of copepodids to reduced salinity levels reduced infection of S. salar. Infection levels at reduced salinity were lower than predicted from the free-swimming survival experiment, suggesting that low salinity compromises the copepodids' ability to sense or respond to the presence of a host. In salinity gradients, copepodids demonstrated avoidance of salinities below 27 ppt, by both altering their swimming behaviour and changing the orientation of passive sinking. Avoidance of low salinity levels may be due to their adverse effects on copepodid physiology, as suggested by the reduction in survival. Sinking rates were also faster in reduced salinity, suggesting that remaining in the water column would be more energetically demanding for the copepodids at reduced salinity. These results show that both survival and host infectivity of L. salmonis are severely compromised by short-term exposure to reduced salinity levels.

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Planktonic Distribution of Sea Lice Larvae, Lepeophtheirus Salmonis, in Killary Harbour, West Coast of Ireland

Cited by 50 publications

References 20 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

Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland

Effect of environmental salinity on sea lice Lepeophtheirus salmonis settlement success

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