Distribution of the larval stages ofLepeophtheirus salmonisin three bays on the west coast of Ireland

Costelloe, M.

doi:10.1006/jmsc.1997.0360

Cited by 23 publications

(20 citation statements)

References 4 publications

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“…These model results concur with field observations that larval sea lice, primarily copepodids, are intermittently found in relatively high abundance in the shallow sub-littoral zone at the head of coastal inlets (Costelloe et al 1998a,b, McKibben & Hay 2004. In Loch Shieldaig, the site of the study by , the inlet tapers sharply towards the river mouth, which may exacerbate the aggregation of lice there.…”

Section: Discussionsupporting

confidence: 88%

Dispersal of sea louse larvae from salmon farms: modelling the influence of environmental conditions and larval behaviour

Gillibrand¹,

Willis²

2007

Aquat. Biol.

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Sea lice are ectoparasitic copepods of farmed and wild salmonids that cost the global salmon aquaculture industry more than US $100 million annually and have been implicated as a contributing factor in the decline of wild salmonid populations in the North Atlantic region. A coupled hydrodynamics-louse-transport model including varying physical forcing and sea louse larval behaviour was developed, and used to investigate: (1) the dispersal of sea louse larvae from a point source in an idealized coastal inlet; (2) the effect of physical processes on louse distributions; and (3) the effect of behavioural processes on louse distributions. The dispersal and distribution of sea louse larvae was strongly influenced by environmental conditions and larval behaviour. In particular, larval diel vertical migration increased the predicted infection risk for wild salmonids, as more sea louse larvae were retained within the inlet and were dispersed more widely with higher average abundance at the surface. When wind forcing was weak or channelled along the inlet, higher louse abundance was predicted along the boundaries, where migrating salmonids tend to congregate. Copepodids were intermittently transported to the river mouth at the head of the inlet during different combinations of river flow and wind forcing, either by surface flows or deeper landward-flowing currents. Mean predicted nauplius abundance peaked near the source of larvae and decreased rapidly with increasing distance from the source, whereas copepodids peaked 7 to 12 km seaward of the source. Realistic environmental forcing and larval behaviour must be incorporated into dispersal models if the spatial and temporal variability of larval sea louse abundance is to be reliably predicted.

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Section: Discussionsupporting

confidence: 88%

Dispersal of sea louse larvae from salmon farms: modelling the influence of environmental conditions and larval behaviour

Gillibrand¹,

Willis²

2007

Aquat. Biol.

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“…Studies of local currents in estuarine areas suggest that larval transport is only possible over long distances if the larvae rest on the sediment during an ebb tide and are only in the water column during the flood tide (Costello et al 1998a,b, Kimmerer et al 1998). This pattern of behaviour was not observed in this study, suggesting that the copepodids remain distributed in the water column as previously proposed by Heuch et al (1995).…”

Section: Discussionmentioning

confidence: 99%

“…No relationship between larval abundance and the number of ovigerous lice on the farm was found (Costello et al 1998a). There is also an indication that the nets surrounding salmon farms restrict water movement, and the majority of hatched larvae are retained within the farm (Costello et al 1996).…”

Section: Introductionmentioning

confidence: 98%

“…Copepodids have been found in high concentrations around river mouths, particularly in spring during the seaward migration of salmon smolts (Costello et al 1998a,b, 2004, Carr & Whoriskey 2004, McKibben & Hay 2004. Lepeophtheirus salmonis copepodids are stenohaline, suggesting their activity and survival would be severely compromised in waters of reduced salinity (Pike & Wadsworth 2000).…”

Section: Introductionmentioning

confidence: 99%

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Effect of environmental salinity on sea lice Lepeophtheirus salmonis settlement success

Bricknell¹,

Dalesman²,

O'Shea³

et al. 2006

Dis. Aquat. Org.

164

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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“…Development from nauplius I to the infectious copepodid can last up to 13 d at 10°C (Johnson & Albright 1991a), resulting in an extremely high spreading potential through passive transport of the planktonic larvae. However, since it is difficult to track invertebrate larvae in the marine environment, little information exists about drift distances of L. salmonis larvae due to wind speed, tidal flow and ocean current (Costelloe et al 1996, Costelloe et al 1998, Asplin et al 2002, McKibben & Hay 2004. In addition to passive transport by water currents, the parasitic stages of the lice may be transported further by its host's migratory pattern.…”

Section: Introductionmentioning

confidence: 99%

Sequence variation in four mitochondrial genes of the salmon louse Lepeophtheirus salmonis

Tjensvoll¹,

Glover²,

Nylund³

2006

Dis. Aquat. Org.

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A total of 210 Lepeophtheirus salmonis collected from 7 locations (Scotland, Russia, Canada, Japan and 3 locations in Norway), were screened for sequence variation in 4 mitochondrial genes; ATPase subunit 6 (A6), Cytochrome b oxidase subunit I (COI ), Cytochrome b (Cyt b) and 16S rRNA. A high level of intraspecific variation was observed within all genes. The majority of polymorphisms were present in single individuals only, which resulted in a high number of private haplotypes within each gene. Little evidence of genetic differentiation was observed among the 3 Norwegian locations or between L. salmonis samples from Norway, Scotland and Russia. Pairwise F ST values indicated that a weak degree of sub-division between L. salmonis sampled in Canada and the Northeast Atlantic might, however, exist. All samples collected in the Atlantic were highly different from the Japanese sample. It is suggested that the lack of genetic differentiation among lice samples from the North Atlantic is a result of extensive gene flow mediated by passive transport of L. salmonis larvae, and the migratory pattern of its salmonid hosts. KEY WORDS: Lepeophtheirus salmonis · A6 · COI · 16S rRNA · Cyt b · Sequence variation · Population genetics · Sea lice Resale or republication not permitted without written consent of the publisherDis Aquat Org 68: [251][252][253][254][255][256][257][258][259] 2006 this area (Berland 1993, Holst et al. 1993, Jacobsen & Gaard 1997.Several authors have investigated the population genetic structure of Lepeophtheirus salmonis (Isdal et al. 1997, Todd et al. 1997, 2004, Nolan et al. 2000, Tully & Nolan 2002, Dixon et al. 2004). Studies of allozymes and random amplification of polymorphic DNA (RAPD) have indicated that different L. salmonis populations may exist in both Norway (Isdal et al. 1997) and Scotland (Todd et al. 1997, Dixon et al. 2004). Genetic differences have also been found between L. salmonis sampled in Norway, Scotland and Ireland (Nolan et al. 2000). However, in a recent study using 6 microsatellite markers, no genetic differentiation was found between samples of L. salmonis collected on wild and farmed salmonids in Scotland, nor between L. salmonis collected on salmonids from Scotland, Norway and Canada (Todd et al. 2004).Mitochondrial DNA (mtDNA) displays a high mutation rate, accumulating substitutions up to 10 times faster than nuclear genes (Shearer et al. 2002). Combined with the fact that these genes are maternally inherited, reducing the effective population size and increasing opportunity for genetic drift, this makes these genes particularly suitable for population genetic studies. Consequently, mitochondrial genes have been extensively used in studies of population structure, patterns of gene flow and phylogenetic relationships (e.g. Hale & Singh 1987, Garcia-Machado et al. 1999, Saito et al. 2000, Schwenk et al. 2000, Umetsu et al. 2002, Gantenbein & Largiader 2003. Cytochrome c oxidase subunit I (COI ), 16S rRNA, ATPase subunit 6 (A6) and Cytochrome b (Cyt b) are am...

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Distribution of the larval stages ofLepeophtheirus salmonisin three bays on the west coast of Ireland

Cited by 23 publications

References 4 publications

Dispersal of sea louse larvae from salmon farms: modelling the influence of environmental conditions and larval behaviour

Dispersal of sea louse larvae from salmon farms: modelling the influence of environmental conditions and larval behaviour

Effect of environmental salinity on sea lice Lepeophtheirus salmonis settlement success

Sequence variation in four mitochondrial genes of the salmon louse Lepeophtheirus salmonis

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