Previous experimental studies have explored the infrapopulation dynamics of Gyrodactylus turnbulli and G. bullatarudis ectoparasites on their fish host, Poecilia reticulata. Here, statistics and mathematical models are used to address three important biological questions concerning parasite microhabitat preference, host survival and parasite virulence based on existing empirical data. Firstly, although these species' respective caudal and rostral preferences on the host are reported, it is unknown whether this is consistent over time and across different fish stocks. We confirmed that the captive-bred G. turnbulli and wild G. bullatarudis strains preferred the caudal and rostral regions respectively across different fish stocks; however, the wild G. turnbulli strain changed microhabitat preference over time, indicating microhabitat preference of gyrodactylids is host and time-dependent. Secondly, we improved previous estimates of survival probabilities using a multi-state Markov model that generalises the standard survival models. Finally, we quantified and compared the virulence of three parasite strains across different fish stocks and sexes, by estimating both host mortality and recovery rates from the multi-state model. It was shown that parasite-related mortalities are host, sex and time-dependent, whereas fish size is confirmed to be the key determinant of host recovery. The model can be expanded for other host-parasite systems.
The R codes and its accompanying Jupyter notebook HTML files (including the empirical data used for the study and other exported study outputs) are attached.