A method of estimating in situ salmon louse nauplii production at fish farms

Norði, Gunnvør á; Simonsen, Knud; Patursson, Øystein

doi:10.3354/aei00185

Cited by 14 publications

(14 citation statements)

References 43 publications

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“…Salmo trutta are vulnerable to infestation with salmon lice because of their surface-oriented behaviour, which overlaps with the distribution of salmon lice larvae (Heuch et al, 1995;á Norði et al, 2016). On the other hand, in coastal areas with a surface layer of fresh water, owing to high influx of fresh water from rivers, S. trutta may be protected against salmon lice due to their surface orientation, because salmon lice do not cope well with freshwater and brackish water (Wootten et al, 1982;Johnson & Albright, 1991;Bricknell et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

Marine depth use of sea trout Salmo trutta in fjord areas of central Norway

Eldøy

Davidsen

Thorstad

et al. 2017

Journal of Fish Biology

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The vertical behaviour of 44 veteran sea trout Salmo trutta (275-580 mm) in different marine fjord habitats (estuary, pelagic, near shore with and without steep cliffs) was documented during May-February by acoustic telemetry. The swimming depth of S. trutta was influenced by habitat, time of day (day v. night), season, seawater temperature and the body length at the time of tagging. Mean swimming depth during May-September was 1·7 m (individual means ranged from 0·4 to 6·4 m). Hence, S. trutta were generally surface oriented, but performed dives down to 24 m. Mean swimming depth in May-September was deeper in the near-shore habitats with or without steep cliffs (2·0 m and 2·5 m, respectively) than in the pelagic areas (1·2 m). May-September mean swimming depth in all habitats was slightly deeper during day (1·9 m) than at night (1·2 m), confirming that S. trutta conducted small-scale diel vertical movements. During summer, S. trutta residing in near-shore habitat progressively moved deeper over the period May (mean 1·1 m) to August (mean 4·0 m) and then reoccupied shallower areas (mean 2·3 m) during September. In winter (November and February), individuals residing in the innermost part of the fjords were found at similar average depths as they occupied during the summer (mean 1·3 m). The swimming depths of S. trutta coincide with the previously known surface orientation of salmon lice Lepeophtheirus salmonis. Combined with previous studies on horizontal use of S. trutta, this study illustrates how S. trutta utilize marine water bodies commonly influenced by anthropogenic factors such as aquaculture, harbours and marine constructions, marine renewable energy production or other human activity. This suggests that the marine behaviour of S. trutta and its susceptibility to coastal anthropogenic factors should be considered in marine planning processes.

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Section: Discussionmentioning

confidence: 99%

Marine depth use of sea trout Salmo trutta in fjord areas of central Norway

Eldøy

Davidsen

Thorstad

et al. 2017

Journal of Fish Biology

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“…Once attached to a host, copepodids eventually develop into adults, and adult females potentially release 26 to 68 nauplii through the protruding egg sacs daily, which then are free to develop to the copepodid stage and to infect other hosts (Heuch et al 2000, á Norði et al 2016. The growth of a sea lice population has an exponential nature (Frazer et al 2012) and is generally modelled as such (Costello 2006, Krkošek et al 2010, Frazer et al 2012.…”

Section: Introductionmentioning

confidence: 99%

Effect of exposure on salmon lice Lepeophtheirus salmonis population dynamics in Faroese salmon farms

Patursson¹,

Simonsen²,

Visser³

et al. 2017

Aquacult. Environ. Interact.

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We assessed variations in salmon lice Lepeophtheirus salmonis population dynamics in Faroese salmon farms in relationship to their physical exposure to local circulation patterns and flushing with adjacent waters. Factors used in this study to quantify physical exposure are estimates of the freshwater exchange rate, the tidal exchange rate and dispersion by tidal currents. Salmon farms were ranked according to the rate of increase in the average numbers of salmon lice per fish. In a multiple linear regression, physical exposure together with temperature were shown to have a significant effect on the rate of lice infection. The sites with low exposure revealed higher rates of self-infection and internally driven outbreak dynamics, while high-exposure sites showed lower rates of self-infection, tending towards externally driven outbreak dynamics. The lowexposure sites also appeared to have a lower threshold of salmon stocking numbers for outbreaks of infection. The study presents a simple method of characterizing salmon farming fjords in terms of their different exposure levels and how they relate to potential self-infection at these sites.

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“…The planktonic larval stages are small, and the larvae have limited swimming capacity; they perform vertical migrations that can optimize their chances of encountering a host. Planktonic larvae are positively phototactic, thus staying in the upper water masses under conditions of low water mixing (Bron et al, 1993;Heuch et al, 1995;Nordi et al, 2016). Nauplii have been shown to prefer higher temperatures, that optimize and accelerate development time to the copepodite stage (Johnson and Albright, 1991;Pike et al, 2006;á Norði et al, 2015), but have also been shown to aggregate underneath thermoclines if the upper water layer is > 12 • C (Crosbie et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Biofouling on Salmon Pen Nets and Cleaner Fish Shelters Does Not Harbor Planktonic Stages of Sea Lice

et al. 2020

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The objective of the current study was to determine the extent to which planktonic sea lice (Lepeophtheirus salmonis Krøyer, 1838 and Caligus elongatus Nordmann, 1832) were present in the biofouling on open-sea net pens used for commercial rearing of Atlantic salmon (Salmo salar L.), and to assess if biofouling organisms on nets act as barriers similar to salmon lice skirts. We have examined two possible interactions of biofouling and planktonic sea lice, the first was if biofouling could function as a microhabitat for planktonic sea lice, with resuspension of sea lice during net cleaning operations. The second interaction was if biofouling may cause a retaining effect on the transport of planktonic stages out of the net pen. These interactions were investigated at different commercial salmon farms. With only one sea louse found among the biofouling on nets and cleaner fish shelters, we found no indication that sea lice utilized biofouling as a reservoir. This was further supported by the lack of impact on the proportion of samples with sea lice and the average density of sea lice in the water following the release of biofouling material during in situ net cleaning. Furthermore, the presence of biofouling had no effect on the proportion of samples with sea lice or the average density of planktonic sea lice in the net pens. The presence of a lice skirt resulted, however, in a significantly higher proportion of samples with planktonic sea lice inside the net pen in one of the two sites utilizing lice skirts. The results of our study suggested that the presence of biofouling has no influence on the average density and proportion of samples with planktonic stages of sea lice and that planktonic sea lice do not inhabit biofouling.

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A method of estimating in situ salmon louse nauplii production at fish farms

Cited by 14 publications

References 43 publications

Marine depth use of sea trout Salmo trutta in fjord areas of central Norway

Marine depth use of sea trout Salmo trutta in fjord areas of central Norway

Effect of exposure on salmon lice Lepeophtheirus salmonis population dynamics in Faroese salmon farms

Biofouling on Salmon Pen Nets and Cleaner Fish Shelters Does Not Harbor Planktonic Stages of Sea Lice

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