Parasites either reduce or increase host vulnerability to fishing: a case study of a parasitic copepod and its salmonid host

Parasites generally increase host vulnerability to predators via host manipulation for trophic transmission and reduction of host activities. Predators also select prey depending on the parasite infection status. Despite such parasites' roles in prey-predator interactions in wild animals, how parasites affect human hunting probability and resource consumption remains unknown. We examined the effects of the ectoparasitic copepod Salmincola cf. markewitschi on fish vulnerability to angling. We found that infected fish were less vulnerable compared with non-infected fish when the fish body condition was low, which was probably due to reduced foraging activity. On the contrary, infected fish were more vulnerable when the host body condition was high, probably due to the compensation of parasites' negative effects. A Twitter analysis also suggested that people avoided eating fish with parasites and that anglers' satisfaction decreased when captured fish were parasitized. Thus, we should consider how animal hunting is affected by parasites not only for catchability but also for avoiding parasite infection sources in many local regions.

Automated summary

Parasites increase host vulnerability to predators through host manipulation and reduction of host activities. Predators also choose prey based on the presence of parasites. Little is known about how parasites affect human hunting probability and resource consumption. This study examined the effects of the ectoparasitic copepod Salmincola cf. markewitschi on fish vulnerability to angling. The findings suggest that infected fish are less vulnerable when their body condition is low, but more vulnerable when their body condition is high. People tend to avoid eating fish with parasites, and anglers' satisfaction decreases when the fish they catch are parasitized. Overall, this study highlights the importance of considering the impact of parasites on animal hunting and resource consumption.