Salmon lice – impact on wild salmonids and salmon aquaculture

Abstract

Salmon lice, Lepeophtheirus salmonis, are naturally occurring parasites of salmon in sea water. Intensive salmon farming provides better conditions for parasite growth and transmission compared with natural conditions, creating problems for both the salmon farming industry and, under certain conditions, wild salmonids. Salmon lice originating from farms negatively impact wild stocks of salmonids, although the extent of the impact is a matter of debate. Estimates from Ireland and Norway indicate an odds ratio of 1.1:1-1.2:1 for sea lice treated Atlantic salmon smolt to survive sea migration compared to untreated smolts. This is considered to have a moderate population regulatory effect. The development of resistance against drugs most commonly used to treat salmon lice is a serious concern for both wild and farmed fish. Several large initiatives have been taken to encourage the development of new strategies, such as vaccines and novel drugs, for the treatment or removal of salmon lice from farmed fish. The newly sequenced salmon louse genome will be an important tool in this work. The use of cleaner fish has emerged as a robust method for controlling salmon lice, and aquaculture production of wrasse is important towards this aim. Salmon lice have large economic consequences for the salmon industry, both as direct costs for the prevention and treatment, but also indirectly through negative public opinion.

High host densities dilute sea lice Lepeophtheirus salmonis loads on individual Atlantic salmon, but do not reduce lice infection success

“…are external parasites responsible for multi-million dollar losses in the salmon industry worldwide (Costello 2009a), and for some of the major ecological impacts associated with marine aquaculture (Krkošek et al 2007, Costello 2009b, Torrissen et al 2013. Sea lice have a multiple-stage life cycle which includes free-swimming larvae and attached moult stages.…”

Trends during development of Scottish salmon farming: An example of sustainable intensification?

“…• Transfer of disease to wild stocks: Despite improved disease con trol within farmed stocks, disease pressures on wild stocks, nota bly from sea-lice, remain a topic of concern (Torrissen et al, 2013;Shepherd and Little, 2014). Pathogen pressures on wild stocks will depend upon pathogen prevalence in farmed stocks, the size of farmed stocks, and the overlap between farmed and wild fish in space and time (McVicar, 1997).…”

Parasitological assessment in the hybrid surubim (Pseudoplatystoma reticulatum x P. corruscans), with uncommon occurrence of Monogenea parasites

“…Šimková et al (2013) argued that the role of fish hybridization on parasite specificity is not yet clear, there may be changes in parasitic fauna due to host co-adaptation, though hybrids may harbor parasites from both parental species. We note that this may pose an important ecological issue, because with higher numbers of cultured fish, natural stocks may be greatly affected by parasites from cultured stocks, a situation seen before in salmonids (MCVICAR, 1997;TORRISSEN et al, 2013).…”