The effect of temperature on ability of Lepeophtheirus salmonis to infect and persist on Atlantic salmon

Abstract

The salmon louse (Lepeophtheirus salmonis) is an ecologically and economically important parasite of salmonid fish. Temperature is a strong influencer of biological processes in salmon lice, with development rate increased at higher temperatures. The successful attachment of lice onto a host is also predicted to be influenced by temperature; however, the correlation of temperature with parasite survival is unknown. This study describes the effects of temperature on infection success, and survival on the host during development to the adult stage. To accurately describe infection dynamics with varying temperatures, infection success was recorded on Atlantic salmon (Salmo salar) between 2 and 10°C. Infection success ranged from 20% to 50% and was strongly correlated with temperature, with the highest success at 10°C. Parasite loss was monitored during development at eight temperatures with high loss of lice at 3 and 24°C, whilst no loss was recorded in the temperature range from 6 to 21°C. Sea temperatures thus have large effects on the outcome of salmon louse infections and should be taken into account in the management and risk assessment of this parasite. Improving understanding of the infection dynamics of salmon lice will facilitate epidemiological modelling efforts and efficiency of pest management strategies.

Temperature affects settlement success of ectoparasitic salmon lice (Lepeophtheirus salmonis) and impacts the immune and stress response of Atlantic salmon (Salmo salar)

“…The reduction in lice survival and infestation success at low temperatures demonstrates that the overall effect of low temperatures is more detrimental to the louse than the host, despite reduced or delayed responses in several immune genes in the latter. This therefore confirms findings in previous studies reporting decreased lice infestation success at low temperatures (Dalvin et al., 2020a; Hamre et al., 2019; Samsing et al., 2016), which could be caused by a reduction in energy reserves at the moult to the infective copepodid stage (Skern‐Mauritzen et al., 2020). The effect of temperature on lice performance reported herein may explain why lice abundances normally are lower at higher latitudes along the Norwegian coast (Jansen et al., 2012; Vollset et al., 2020).…”

“…During the infection inflow of water was maintained (12 L/min), but the outlet was blocked until the normal water level was restored. Infection success of salmon lice is temperature dependent (Dalvin et al., 2020a; Skern‐Mauritzen et al., 2020), hence the number of copepodids per tank was adjusted to achieve similar lice intensities on the fish at different temperatures (i.e., 4°C, 1008 lice/tank; 8°C, 672 lice/tank; 12°C, 525 lice/tank and 16°C, 462 lice/tank). Fish in the control tanks were equally treated, but no copepodids were added to the tank.…”

“…Additionally, temperatures vary seasonally, with the lowest temperatures in late winter. Salmon lice are ectothermic, and temperature influence their physiology such as development time, fecundity, infestation success, longevity, egg and body size (Boxaspen & Næss, 2000; Dalvin et al., 2020a; Hamre et al., 2019; Heuch et al., 2000, 2003; Nordhagen et al., 2000; Samsing et al., 2016; Skern‐Mauritzen et al., 2020). Moreover, temperature could affect epidemiology by altering the generation time and the net reproductive rate of the louse (Groner et al., 2016).…”

Salmon louse infestation levels on sea trout can be predicted from a hydrodynamic lice dispersal model

“…Previous experimental studies have shown significant mortality of lice on Atlantic salmon, mainly in the pre-adult and adult stages (Bui et al, 2016;Hamre & Nilsen, 2011). Other studies have shown that nearly 100% of the lice survives to pre-adult and adult stages (Bui et al, 2018), except at extreme temperatures not relevant for Norwegian field conditions (Dalvin et al, 2020).…”

Connections between "Extreme Marine Events" and Biological EOVs Report

“…The total number of Lepeophtheirus salmonis per fish recorded at the Deenish Island salmon farm are reported here together with the temperature and DO series. According to Dalvin et al (2020), temperature is a strong influencer of biological processes in salmon lice, with development rate increased at higher temperatures. However, there are many other factors apart from seawater temperature influencing the populations of sea lice.…”