Salmon lice infection of wild sea trout and Arctic char in marine and freshwaters: the effects of salmon farms

By P. Bjørn, B. Finstad, R. Kristoffersen. 2001

198 citations recorded by the source corpus.

The abundance of salmon lice and the physiological effects of infection were examined in two stocks of sympatric sea trout and anadromous Arctic char in northern Norway. One stock feed in a coastal area with extensive salmon farming (exposed locality), while the other feed in a region with little farming activity (unexposed locality). The results showed that the lice infection was significantly higher at the exposed locality, at which the mean intensity of infection peaked in June and July at over 100 and 200 lice larvae per fish respectively. At the exposed locality we also observed a premature return to freshwater of the most heavily infected fish. Such behaviour has previously been interpreted as a response by the fish to reduce the stress caused by the infection and/or to enhance survival. Blood samples taken from sea trout at sea at the exposed locality showed a positive correlation between intensity of parasite infection and an increase in the plasma cortisol, chloride and blood glucose concentrations, while the correlations from sea trout in freshwater were more casual. Several indices pointed towards an excessive mortality of the heaviest infected fish, and 47% of the fish caught in freshwater and 32% of those captured at sea carried lice at intensities above the level that has been shown to induce mortality in laboratory experiments. Furthermore, almost half of all fish from the exposed locality had lice intensities that would probably cause osmoregulatory imbalance. High salmon lice infections may therefore have profound negative effects upon wild populations of sea trout. At the unexposed location, the infection intensities were low, and few fish carried more than 10 lice. These are probably within the normal range of natural infection and such intensities are not expected to affect the stock negatively.

Subfields: Aquatic Science, Ecology, Parasitology

View Paper: https://www.semanticscholar.org/paper/61d0e2c839b93767260f0f80d90d016573e3b613

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Aquatic Science

1. P. Bjørn
2. B. Finstad
3. F. Økland
4. J. Bayle-Sempere
5. P. Sanchez‐Jerez
6. Frank Asche
7. E. Thorstad
8. T. Dempster

In Ecology

1. T. Dempster
2. K. Boxaspen
3. P. Sanchez‐Jerez
4. L. Asplin
5. P. Bjørn
6. J. Bayle-Sempere
7. B. Finstad
8. M. Berg

In Parasitology

1. K. Boxaspen
2. L. Asplin
3. P. Bjørn
4. B. Finstad
5. M. Berg
6. T. Dempster
7. R. Serra-Llinares
8. Alf Harbitz

Citations in the corpus

• Migration speeds and orientation of Atlantic salmon and sea trout post-smolts in a Norwegian fjord system (2004, background): “During the last decades, intensive fish farming in fjord and coastal areas has led to higher concentrations of salmon lice, Lepeophtheirus salmonis Kroyer (Heuch & Mo 2001), and salmon lice infestations have been reported to cause significant sub-lethal and lethal effects on wild Atlantic salmon and”
• Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review (2015, background): “…intensive traps, draft nets, and included in analysis electrofishing Gill nets Mean = 119−209 g Vesterålen (northern Norway) Intensive farming Bjørn et al. (2001)a Gill nets Mean = 119−464 g Ofoten (northern Norway) Low farming intensity Bjørn et al. (2001)a Gill nets Not given (gill net…”
• The Cost of Lice: Quantifying the Impacts of Parasitic Sea Lice on Farmed Salmon (2017, background): “…literature on the transmission dynamics of farm-to-wild salmon lice spillover (Krkosek, Lewis, and Volpe 2005; Price et al. 2011) and the subsequent ecological effects on wild salmonids (Krkosek and Hilborn 2011; Costello 2009; Bjørn, Finstad, and Kristoffersen 2001; Finstad et al. 2000).”
• Attraction of wild fish to sea-cage fish farms in the south-western Mediterranean Sea: spatial and short-term temporal variability (2002, background): “…aquaculture and wild fish stocks have been widely documented (Naylor et al. 2000), and include transfer of antibiotics used in farm feeds to wild fish (Bjoerklund et al. 1991) and transmission of disease and parasites from caged fishes (Saunders 1991, Johnsen & Jensen 1994, Bjorn et al. 2001).”
• Extensive Aggregations of Wild Fish at Coastal Sea-Cage Fish Farms (2004, background): “While evidence exists for non-direct transfer of pathogens form caged to wild fish for salmonids ( Bjorn et al., 2001 ), there are no comprehensive studies on the impacts of fish farms on parasite loads of other species of wild fish.”
• Salmon lice, Lepeophtheirus salmonis (Krøyer), infestation in sympatric populations of Arctic char, Salvelinus alpinus (L.), and sea trout, Salmo trutta (L.), in areas near and distant from salmon farms (2002, background): “This may give a biased indication of the lice infection in the total sea-going population (Birkeland and Jakobsen, 1997; Bjørn et al., 2001), and stresses the need for estimates of the infestation level on lice hosts at sea.”
• Disease interaction and pathogens exchange between wild and farmed fish populations with special reference to Norway (2011, background): “Salmon lice have typically been found at rather high prevalence but low intensity, probably in a quite regulated and stable host-parasite system, and few adverse effects on the host population have been observed (Bjørn et al., 2001; Boxshall, 1974; Krkošek et al., 2005; Krkošek et al., 2006b; Pember”
• High connectivity of salmon farms revealed by aggregation, residence and repeated movements of wild fish among farms (2009, background): “…WORDS: Aquaculture · Sea-cage · Aggregation · Movement · Pollachius virens · Tagging · Tracking Resale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 384: 251–260, 2009 sea lice infestations of wild salmonids (Bjørn et al. 2001, Krkosek et al. 2007).”
• A review of the biology and genetics of sea lice (2006, background): “…resulting in their premature return to fresh water 1054-3139/$32.00 2006 International Co from https://academic.oup.com/icesjms/article-abstract/63/7/1304/ 2018 or mortality at sea (Birkeland, 1996; Birkeland and Jakobsen, 1997; Tully et al., 1999; Bjørn et al., 2001; Bjørn and Finstad, 2002).”
• Salmon lice infection on wild salmonids in marine protected areas: an evaluation of the Norwegian 'National Salmon Fjords' (2014, background): “Based on a number of studies undertaken both in Norway (Grimnes & Jakobsen 1996, Bjørn & Finstad 1997, Finstad et al. 2000, 2011, Bjørn et al. 2001, Holst et al. 2003, Wagner et al. 2003, 2008, Tveiten et al. 2010, Finstad & Bjørn 2011) and in other countries (Nolan et al. 1999, Johnson & Fast…”