Data for: Ectoparasite population dynamics affected by host body size but not host density or water temperature in a 32-year long time series

Host density, host body size, and ambient temperature have all been
positively associated with increases in parasite infection. However, the
relative importance of these factors in shaping long-term parasite
population dynamics in wild host populations is unknown due to the absence
of long-term studies. Here, we examine long-term drivers of gill lice
(Copepoda) infections in Arctic charr (Salmonidae) over 32 years. We
predicted that host density and body size and water temperature would all
positively affect parasite population size and population growth rate. Our
results show that fish size was the main driver of gill lice infections in
Arctic charr. In addition, Arctic charr became infected at smaller sizes
and with more parasites in years of higher brown trout population size.
Negative intraguild interactions between brown trout and Arctic charr
appear to drive smaller Arctic charr to seek refuge in deeper areas of the
lake, thus increasing infection risk. There was no effect of host density
on the force of infection, and the relationship between Arctic charr
density and parasite mean abundance was negative, possibly due to an
encounter-dilution effect. The population densities of host and parasite
fluctuated independently of one another. Water temperature had negligible
effects on the temporal dynamics of the gill lice population.
Understanding long-term drivers of parasite population dynamics is key for
research and management. In fish farms, artificially high densities of
hosts lead to vast increases in the transmission of parasitic copepods.
However, in wild fish populations fluctuating at natural densities, the
surface area available for copepodid attachment might be more important
than the density of available hosts.