Present Status and Implications of Salmon Lice on Wild Salmonids in Norwegian Coastal Zones

Finstad, Bengt; Bjørn, Pål Arne

doi:10.1002/9780470961568.ch9

Cited by 20 publications

(11 citation statements)

References 81 publications

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“…Infestations were modelled as a binary above/below threshold variable. Using a critical threshold level of infestation, rather than modelling the presence/absence of lice, focuses on infestations that are likely to be detrimental to individuals (Middlemas et al 2010;Finstad & Bjørn 2011). In laboratory studies, Wells et al (2006) found that abrupt changes in a range of physiological parameters occurred at 13 mobile lice per trout (weight range 19-70 g) and suggested that this level be used to indicate the proportion of trout subject to physiological stress and potential death from sea lice infestations.…”

Section: Discussionmentioning

confidence: 99%

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Relationship between sea lice levels on sea trout and fish farm activity in western Scotland

Middlemas

Fryer

Tulett

et al. 2012

Fisheries Management Eco

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The relationship between aquaculture and infestations of sea lice on sea trout, Salmo trutta L., is controversial. Here, the association between sea lice infestations on wild sea trout and characteristics of local Atlantic salmon, Salmo salar L., farms were investigated using data collected on the Scottish west coast. The proportion of sea trout with louse burdens above a critical level was positively related to the fork length of the sea trout and the mean weight of salmon on the nearest fish farm, and negatively related to the distance to that farm. The distance to the nearest fish farm did not influence the probability of infestations above the critical level beyond 31 km although there was considerable uncertainty around this cut‐off distance (95% limits: 13–149 km). The results support a link between Atlantic salmon farms and sea lice burdens on sea trout in the west of Scotland and provide the type of information required for marine spatial planning.

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Section: Discussionmentioning

confidence: 99%

“…Using a critical threshold level of infestation, rather than modelling the presence/absence of lice, focuses on infestations that are likely to be detrimental to individuals (Middlemas et al . ; Finstad & Bjørn ). In laboratory studies, Wells et al .…”

Section: Methodsmentioning

confidence: 99%

Relationship between sea lice levels on sea trout and fish farm activity in western Scotland

Middlemas

Fryer

Tulett

et al. 2012

Fisheries Management Eco

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“…During the last 30 years, salmon farming has increased the abundance of sea lice (Finstad & Bjørn, 2011;Fjørtoft et al, 2017;Thorstad & Finstad, 2018;Thorstad et al, 2015;Tully, Poole, Whelan, & Merigoux, 1993). During the last 30 years, salmon farming has increased the abundance of sea lice (Finstad & Bjørn, 2011;Fjørtoft et al, 2017;Thorstad & Finstad, 2018;Thorstad et al, 2015;Tully, Poole, Whelan, & Merigoux, 1993).…”

Section: Sea Licementioning

confidence: 99%

Environmental influences on life history strategies in partially anadromous brown trout (Salmo trutta, Salmonidae)

et al. 2019

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This paper reviews the life history of brown trout and factors influencing decisions to migrate. Decisions that maximize fitness appear dependent on size at age. In partly anadromous populations, individuals that attain maturity at the parr stage typically become freshwater resident. For individual fish, the life history is not genetically fixed and can be modified by the previous growth history and energetic state in early life. This phenotypic plasticity may be influenced by epigenetic modifications of the genome. Thus, factors influencing survival and growth determine life‐history decisions. These are intra‐ and interspecific competition, feeding and shelter opportunities in freshwater and salt water, temperature in alternative habitats and flow conditions in running water. Male trout exhibit alternative mating strategies and can spawn as a subordinate sneaker or a dominant competitor. Females do not exhibit alternative mating behaviour. The relationship between growth, size and reproductive success differs between sexes in that females exhibit a higher tendency to migrate than males. Southern populations are sensitive to global warming. In addition, fisheries, aquaculture with increased spreading of salmon lice, introduction of new species, weirs and river regulation, poor water quality and coastal developments all threaten trout populations. The paper summarizes life‐history data from six populations across Europe and ends by presenting new research questions and directions for future research.

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Section: Discussionmentioning

confidence: 99%

“…Thus, the majority of marine mortalities for both groups occur the first few days following migration to sea. Further out in the fjord system, salmon lice Lepeophtheirus salmonis constitutes a threat to S. salar post-smolts before they leave for the open ocean (Finstad & Bjørn, 2011;Krkoŝek et al, 2013). It is generally believed that size of S. salar smolts and post-smolts is important for marine survival, mainly due to predator avoidance and the ability to withstand unfavourable environmental conditions (Salminen et al, 1994(Salminen et al, , 1995Kallio-Nyberg et al, 1999;Saloniemi et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Passing a seawater challenge test is not indicative of hatchery‐reared Atlantic salmon Salmo salar smolts performing as well at sea as their naturally produced conspecifics

Jensen

Berg

Bremset

et al. 2016

Journal of Fish Biology

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Despite satisfactory reactions to seawater challenge tests indicative of appropriate physiological state, hatchery-reared Atlantic salmon Salmo salar smolts stocked in the Eira River in Norway between 2001 and 2011 performed less well at sea in terms of growth, age at maturity and survival than smolts of natural origin. The mean rates of return to the river for hatchery-reared and naturally produced S. salar were 0·98 and 2·35%. In the Eira River, c. 50 000 hatchery-reared S. salar smolts of local origin were stocked annually to compensate for reduced natural smolt production following regulation for hydroelectric purposes, while a mean of 17 262 smolts were produced naturally in the river. This study demonstrates that, although captive S. salar perform well in seawater challenge tests, hatchery-reared smolts are not necessarily as adaptable to marine life as their naturally produced counterparts. These findings suggest that production of hatchery-reared smolts more similar to naturally produced individuals in morphology, physiology and behaviour will be necessary to improve success of hatchery releases. Where possible, supplementary or alternative measures, including habitat restoration, could be implemented to ensure the long-term viability of wild stocks.

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Present Status and Implications of Salmon Lice on Wild Salmonids in Norwegian Coastal Zones

Cited by 20 publications

References 81 publications

Relationship between sea lice levels on sea trout and fish farm activity in western Scotland

Relationship between sea lice levels on sea trout and fish farm activity in western Scotland

Environmental influences on life history strategies in partially anadromous brown trout (Salmo trutta, Salmonidae)

Passing a seawater challenge test is not indicative of hatchery‐reared Atlantic salmon Salmo salar smolts performing as well at sea as their naturally produced conspecifics

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