Production, mortality, and infectivity of planktonic larval sea lice, Lepeophtheirus salmonis (Krøyer, 1837): current knowledge and implications for epidemiological modelling (original) (raw)
Related papers
Aquaculture Research, 1992
Abstract. Samples of Atlantic salmon, Salmo salar L., held in sea cages and tanks with running water were examined for presence of sea lice, Lepeophtheirus salmonis. The number of lice, their sex stage (only post-chalimus stages) and location on the fish body were recorded. A new method has been used to express parasitic intensity in fish of different size. Effects of different factors on the degree and character of infestation (structure of the lice population), such as fish size, habitat and chemical treatment, have been studied. Different lice categories have shown different susceptibility to delousing with dichlorvos. Second pre-adults are most susceptible, and males generally more than females. Running water has been found to‘flush out’the lice from the fish body. Pre-adults are flushed out easier than adults, and males generally easier than females. Adult males show high tolerance to water of lowered salinity and great mobility manifested in occasional transfer between hosts. The higher activity level of adult males may partly explain a drop in proportion of males after delousing and in running water. Frequency of mating has been found to increase with parasitic intensity.
Frontiers in Marine Science, 2021
The present article reports the densities of planktonic sea lice (Lepeophtheirus salmonis and Caligus elongatus) in three Atlantic salmon (Salmo salar) localities, and the relationship between the abundance of adult sea lice on the salmon and the densities of planktonic sea lice stages, during a complete production cycle followed by a fallowing period. Samples were taken downstream inside and immediately outside of cages, at one locality with lice skirts and two localities without lice skirts. There were no differences in densities of planktonic sea lice in samples taken from the inside or the outside of cages for any of the localities. However, the proportion-non-zero of planktonic sea lice samples taken from inside the cage was higher during months with a temperature above 9 • C (mean abundance: 0.40-2.5 individuals m −3) than months with temperature below 9 • C (mean abundance: 0.02-0.21 individuals m −3 , odds ratio of the proportion-non-zero: p < 0.01). Densities of planktonic sea lice correlated most strongly with temperature in the first year (τ = 0.44-0.57, p < 0.05). A significant correlation between the number of adult female lice on salmon and average density of plankton sea lice was found in the locality with lice skirts during the second year (τ = 0.43 inside cages, τ = 0.58 outside cages, both p values < 0.05). Background levels of planktonic sea lice in the succeeding fallowing period showed neither L. salmonis nor C. elongatus planktonic sea lice, suggesting that there was successful reduction of the densities of planktonic sea lice for this area during the fallowing period.
ICES Journal of Marine Science: Journal du Conseil, 2016
Sea trout are parasitized by two species of caligid copepod sea lice, Lepeophtheirus salmonis and Caligus elongatus. Generally, levels of lice infestation are low and few adverse effects on the host have been reported. However, with the advent of marine salmon farming since the 1980s, there have been many published accounts of L. salmonis sea lice epizootics on salmonids in aquaculture areas. Few large-scale studies are available on levels of sea lice infestation of sea trout in areas without salmon farms or before their development. Understanding natural background lice levels on sea trout is important to interpret lice levels on trout in aquaculture areas. The Celtic Sea Trout Project, an INTERREG IVA Ireland Wales EU funded project, examined the status, distribution, genetics, and ecology of sea trout around the Irish Sea and provided an opportunity to assess levels of lice on sea trout spatially and temporally in an area without marine salmon farming. The prevalence of L. salmon...
The Canadian Field-Naturalist, 2006
Recent recurring infestations of Sea Lice, Lepeophtheirus salmonis, on juvenile Pacific salmon (Oncorhynchus spp.) and subsequent annual declines of these stocks have made it imperative to identify the source of Sea Lice. While several studies now identify farm salmon populations as sources of Sea Louse larvae, it is unclear to what extent wild salmonid hosts also contribute Sea Lice. We measured Sea Louse numbers on adult Pink Salmon (Oncorhynchus gorbuscha) migrating inshore. We also measured Sea Louse numbers on wild juvenile Pink and Chum salmon (Oncorhynchus keta) migrating to sea before the adults returned, and as the two age cohorts mingled. Adult Pink Salmon carried an average of 9.89 (SE 0.90) gravid lice per fish, and thus were capable of infecting the adjacent juveniles. Salinity and temperature remained favourable to Sea Louse reproduction throughout the study. However, all accepted measures of Sea Louse infestation failed to show significant increase on the juvenile sal...
Journal of fish diseases, 2017
The sea louse, Lepeophtheirus salmonis, is parasitic to salmonid species in the Northern Hemisphere and has become a widespread biological and economic problem for the salmon farming industry. A better understanding is needed of their spatial distribution and early life history to disrupt the life cycle of the sea louse. In this study, sea lice larval densities within salmon farms, between salmon farms and reference sites, and at various depths were quantified using both plankton pumps and plankton nets. Farm sites exhibited significantly higher densities than reference sites; however, these densities dropped an order of magnitude at a distance of 100 m from the cages. The majority of the larvae captured in the study were nauplii (93%), and densities ranged from 0 to 10 larvae/m . Free-swimming sea lice larvae were found to exhibit a diel cycle where nauplii larvae were in deeper waters (10-17 m) during the day and in surface waters (1-6 m) during the night. The results of this stud...
Sea lice and salmon population dynamics: effects of exposure time for migratory fish
Proceedings of the Royal Society B: Biological Sciences, 2009
The ecological impact of parasite transmission from fish farms is probably mediated by the migration of wild fishes, which determines the period of exposure to parasites. For Pacific salmon and the parasitic sea louse, Lepeophtheirus salmonis, analysis of the exposure period may resolve conflicting observations of epizootic mortality in field studies and parasite rejection in experiments. This is because exposure periods can differ by 2-3 orders of magnitude, ranging from months in the field to hours in experiments. We developed a mathematical model of salmon-louse population dynamics, parametrized by a study that monitored naturally infected juvenile salmon held in ocean enclosures. Analysis of replicated trials indicates that lice suffer high mortality, particularly during pre-adult stages. The model suggests louse populations rapidly decline following brief exposure of juvenile salmon, similar to laboratory study designs and data. However, when the exposure period lasts for several weeks, as occurs when juvenile salmon migrate past salmon farms, the model predicts that lice accumulate to abundances that can elevate salmon mortality and depress salmon populations. The duration of parasite exposure is probably critical to salmon-louse population dynamics, and should therefore be accommodated in coastal planning and management where fish farms are situated on wild fish migration routes.
Sea lice levels on wild Atlantic salmon, Salmo salar L., returning to the coast of Ireland
Journal of Fish Diseases, 2013
The sea lice population structure, prevalence and intensity of Lepeophtheirus salmonis have been studied over a period extending from 2004 to 2011. Infestation data were collected from the interceptor drift net fishery from 2004 until it was closed in 2006. From 2010, data were collected from the inshore draft net fishery. In all, 34 samples from the drift and draft net fisheries have been analysed to date. Prevalence of infestation with L. salmonis regularly approached 100% in samples of hosts recovered from the offshore drift net fishery. Abundance was variable both within and between years with a maximum mean abundance of 25.8 lice per fish recorded in 2004. The population structure of L. salmonis on hosts recovered in the inshore and estuarine draft net fisheries was different from that observed in the more offshore drift net samples. There is clear evidence of recent infestation with L. salmonis in the draft net samples.