The Effect of Sea Lice on Atlantic Salmon and other Salmonid Species

Finstad, Bengt; Bjørn, Pål Arne; Todd, Christopher; Whoriskey, Fred; Gargan, Patrick; Forde, G.P.; Revie, Crawford W.

doi:10.1002/9781444327755.ch10

Cited by 19 publications

(22 citation statements)

References 104 publications

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“…The values suggested by Taranger et al (2015) are intended for populationlevel effects (i.e. % mortality), while individual tolerance levels may be highly variable (Finstad & Bjørn 2011). This should be a future topic of research.…”

Section: Discussionmentioning

confidence: 99%

“…Hence, some important biological information is lost by grouping all stages of salmon lice together. Another reason why salmon lice infestations, like many parasite infestations, are notoriously difficult to study is that the likelihood of a fish to be collected in the monitoring programme is dependent on its infestation level, since salmon lice influence the survival and behaviour of the fish (Finstad & Bjørn 2011). However, studies that include acoustic telemetry may shed light on fish movements in the fjords as well as behavioural differences between individuals with and without lice, as recently illustrated by Gjelland et al (2014).…”

Section: Discussionmentioning

confidence: 99%

“…The lice are transmitted between hosts, as planktonic larvae are free-living in seawater, and older stages attach to fish where they feed on mucus, skin and blood (Pike & Wadsworth 1999, Boxaspen 2006. High infestations may reduce the immune system and growth of the fish and cause increased mortality (Todd et al 2000, Revie et al 2009, Finstad & Bjørn 2011, Finstad et al 2011. The development and reproductive rates of salmon lice are temperature dependent, and their survival is significantly reduced at salinities below 20 ‰ (Stien et al 2005, Bricknell et al 2006.…”

Section: Introductionmentioning

confidence: 99%

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Statistical and ecological challenges of monitoring parasitic salmon lice infestations in wild salmonid fish stocks

Helland¹,

Uglem²,

Jansen³

et al. 2015

Aquacult. Environ. Interact.

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Ecological monitoring programmes should provide precise data to inform management, but the data quality is often limited by methodological challenges and the need for cost-effective sampling. Parasite infestations are particularly challenging to monitor due to complex interactions among hosts, parasites and the environment. In Norway, salmon lice infestations on wild salmonid fish have been monitored since 1992 to survey the potential transmission between farmed and wild salmonids. Here, we compared spatiotemporal variation in salmon lice levels with variations in local fjord conditions, including salinity, temperature and infestation pressure from salmon farms (measured as mean abundance of mature female lice × number of farmed fish). We tested 3 different measures of infestation with different statistical properties. Our results confirm that, even after correcting for temperature and salinity effects, infestation pressure from salmon farms significantly increases the probability of lice infestation in wild salmonids. The probability of infestation increases with fish body length, salmon farm infestation pressure and tem perature, and decreases with increasing freshwater influence. Furthermore, we found a significant interaction between temperature and infestation pressure from salmon farms. When the infestation pressure from farms is low, temperature has a strong increasing effect on the probability of infestation, but as the infestation pressure from farms increases, temperature gradually becomes less important. The exact results vary somewhat depending on the measure of lice infestations used, but the same trend can be seen in all models. We discuss the statistical and biological complexities that make monitoring of salmon lice in wild populations challenging.Variation in salmon lice levels on wild salmonids have been monitored along the entire Norwegian coast.Photo: Bengt Finstad. Map: Ingeborg P. Helland

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Statistical and ecological challenges of monitoring parasitic salmon lice infestations in wild salmonid fish stocks

Helland¹,

Uglem²,

Jansen³

et al. 2015

Aquacult. Environ. Interact.

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“…Gausen & Moen 1991;Heggberget et al 1993) and in North America (e.g. Ford & Myers 2008) and the potential for interactions as a result of outbreeding and subsequent loss of fitness (McGinnity et al 2003), competition for food and space (Jonsson & Jonsson 2011), disruption of breeding behaviour (Fleming et al 2000;Jensen et al 2010) and transmission of disease and parasites (Finstad et al 2011;Harris et al 2011). This is often a result of observations showing declines in wild stocks in areas proximate to aquaculture operations (e.g.…”

Section: Introductionmentioning

confidence: 99%

Incidence and timing of wild and escaped farmed Atlantic salmon (Salmo salar) in Norwegian rivers inferred from video surveillance monitoring

Svenning

Lamberg²,

Dempson

et al. 2016

Ecology of Freshwater Fish

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Run timing of escaped farmed Atlantic salmon Salmo salar vs. wild fish was compared by the use of video camera surveillance in 15 rivers over several years, covering 1600 km of the Norwegian coastline (from 58°N to 69°N). Annual runs of wild salmon varied among rivers from <200 fish to more than 10 000. During the surveillance period that for most rivers extended from late May to early October, larger-sized salmon (fish ≥ 65 cm) generally entered the rivers earlier than small fish. The percentage of salmon identified as escaped farmed fish ranged from 0.1% to 17% across rivers with an average of 4.3%. Estimates of escapees are, however, assumed to represent minimum values because an unknown number of farmed fish passing the video cameras may have been misclassified as wild fish. By the use of a linear mixed model and generalised additive mixed models, it was found that the relationship between run timing and fish length differed significantly between farmed and wild salmon. While small-sized farmed and wild fish (<65 cm) entered the river at about the same time, wild large salmon returned on average 1-2 weeks earlier than similarly sized escapees. The proportion of large-sized farmed escapees also increased until late August and decreased thereafter. In contrast, there was a relatively constant and lower proportion of small-sized escapees throughout the season. Within the surveillance period, there was no evidence of any exceptionally late runs of fish classified as escaped farmed salmon.

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“…al 1996. In Norway, for instance, the freshwater monogenean Gyrodactylus salaris and the marine copepod Lepeophtheirus sal monis are known to be partially responsible for the decline in the numbers of S. salar during the last few decades (Johnsen & Jensen 1991, Heuch et al 2005, Finstad et al 2011, Harris et al 2011. Another pa ra site species that has previously been recorded on Norwegian S. salar with high abundances is the salmon gill maggot Salmincola salmoneus (Smith 1983, Ber land 1993, but to our knowledge no studies on the population dynamics of this parasite have so far been published.…”

Section: Introductionmentioning

confidence: 99%

Population dynamics of Salmincola salmoneus on Atlantic salmon in a northern Norwegian river

Kusterle¹,

Kristoffersen²,

Rikardsen³

2012

Dis. Aquat. Org.

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Atlantic salmon Salmo salar are often heavily infected by the gill maggot Salmincola salmoneus, but little information exists on the population dynamics of this parasite. Through a combination of in vivo field examination and laboratory analysis of gills from the Alta River S. salar population in northern Norway, we describe the population dynamics of the parasite and suggest a model for the host−parasite interactions. S. salar did not become infected with S. salmoneus until they returned to the river as first-time spawners. The infection increased rapidly until autumn, and just after spawning 96% of the spent fish (kelts) were infected with a mean intensity of 53 parasites per fish. In May, the prevalence of S. salmoneus on the descending kelts had increased to 100%, but the intensity exhibited little change. A small proportion of the adult S. salar population returned as immature to the river during autumn and had lower parasite intensities than the kelts the following spring. When the fish that had spawned previously (repeat spawners) returned from their second (or more) sea migration, they had an average infection rate of 36 S. salmoneus individuals per fish. The kelts seemed to be the main habitat for the parasite during winter and spring, and they stay long enough in the river to pass the infection to maiden S. salar that enter the river early in summer. These fish then became a source of infection for the maiden fish entering the river later. However, in years that have a possible mismatch between the opposite migration of kelts and maiden S. salar, the immature fall-running and returning repeat spawners will be crucial for maintaining the parasite population. We hypothesize that heavily infected S. salar may suffer reduced growth and survival at sea, potentially reducing the abundance of repeat spawners.

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The Effect of Sea Lice on Atlantic Salmon and other Salmonid Species

Cited by 19 publications

References 104 publications

Statistical and ecological challenges of monitoring parasitic salmon lice infestations in wild salmonid fish stocks

Statistical and ecological challenges of monitoring parasitic salmon lice infestations in wild salmonid fish stocks

Incidence and timing of wild and escaped farmed Atlantic salmon (Salmo salar) in Norwegian rivers inferred from video surveillance monitoring

Population dynamics of Salmincola salmoneus on Atlantic salmon in a northern Norwegian river

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