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. 2020 Apr 8;10(9):4031-4043.
doi: 10.1002/ece3.6173. eCollection 2020 May.

Seasonal dietary shifts enhance parasite transmission to lake salmonids during ice cover

Sebastian Prati  1 , Eirik H Henriksen  1 , Rune Knudsen  1 , Per-Arne Amundsen  1
Affiliations

Seasonal dietary shifts enhance parasite transmission to lake salmonids during ice cover

Sebastian Prati et al. Ecol Evol. .

Abstract

Changes in abiotic and biotic factors between seasons in subarctic lake systems are often profound, potentially affecting the community structure and population dynamics of parasites over the annual cycle. However, few winter studies exist and interactions between fish hosts and their parasites are typically confined to snapshot studies restricted to the summer season whereas host-parasite dynamics during the ice-covered period rarely have been explored. The present study addresses seasonal patterns in the infections of intestinal parasites and their association with the diet of sympatric living Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) in Lake Takvatn, a subarctic lake in northern Norway. In total, 354 Arctic charr and 203 brown trout were sampled from the littoral habitat between June 2017 and May 2018. Six trophically transmitted intestinal parasite taxa were identified and quantified, and their seasonal variations were contrasted with dietary information from both stomachs and intestines of the fish. The winter period proved to be an important transmission window for parasites, with increased prevalence and intensity of amphipod-transmitted parasites in Arctic charr and parasites transmitted through fish prey in brown trout. In Arctic charr, seasonal patterns in parasite infections resulted mainly from temporal changes in diet toward amphipods, whereas host body size and the utilization of fish prey were the main drivers in brown trout. The overall dynamics in the community structure of parasites chiefly mirrored the seasonal dietary shifts of their fish hosts.

Keywords: Salmo trutta; Salvelinus alpinus; seasonality; subarctic; winter.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Figure 1
Figure 1
Examples of intestinal parasites of Arctic charr and brown trout: Dibothriocephalus sp. (upper‐left corner), C. truncatus (lower‐left corner), Crepidostomum sp. (center), Proteocephalus sp. (upper‐right corner), and E. salvelini (lower‐right corner)
Figure 2
Figure 2
(a) Frequency distribution of the number of intestinal parasites taxa and (b) their prevalence in Arctic charr and brown trout (Cre. = Crepidostomum spp., Cya. = C. truncatus, Eub.s. = E. salvelini, Eub.c. = E. crassum, Pro. = Proteocephalus sp., and Dib. = Dibothriocephalus spp.)
Figure 3
Figure 3
Prevalence and mean intensity (with 95% confidence intervals) of intestinal parasites in Arctic charr and brown trout throughout the main seasons (S = summer, A = autumn, EW = early winter, LW = late winter, Cre. = Crepidostomum spp., Cya. = C. truncatus, Eub.s. = E. salvelini, Eub.c. = E. crassum, Pro. = Proteocephalus sp., and Dib. = Dibothriocephalus spp.)
Figure 4
Figure 4
Nonmetric multidimensional scaling (NMDS) plot on Bray–Curtis distances of (a) Arctic charr and (b) brown trout showing dissimilarity in parasite community composition between seasons including 95% confidence intervals ellipses (Cre. = Crepidostomum spp., Cya. = C. truncatus, Eub.s. = E. salvelini, Eub.c. = E. crassum, Pro. = Proteocephalus sp., and Dib. = Dibothriocephalus spp.). NMDS converged on a three‐dimensional solution with an acceptable stress level
Figure 5
Figure 5
Seasonal variations in the frequency of occurrence of prey categories in the diet of Arctic charr (a) and brown trout (b) (S = summer, A = autumn, EW = early winter, LW = late winter, Amp. = amphipods, Ins.l. = insects larvae, Zoo. = zooplankton, and Fis. = fish). Prey categories not related to intestinal parasite transmission are excluded
Figure 6
Figure 6
Canonical correspondence analysis (CCA) performed on parasite abundances as a function of presence‐absence of prey types and fish length in (a) Arctic charr and (b) brown trout. (Cre. = Crepidostomum spp., Cya. = C. truncatus, Eub.s. = E. salvelini, Eub.c. = E. crassum, Pro. = Proteocephalus sp., and Dib. = Dibothriocephalus spp.)
Figure 7
Figure 7
Differences in parasite community composition between Arctic charr and brown trout using nonmetric multidimensional scaling (NMDS) plot on Bray–Curtis distances including 95% confidence interval ellipses (Cre. = Crepidostomum spp., Cya. = C. truncatus, Eub.s. = E. salvelini, Eub.c. = E. crassum, Pro. = Proteocephalus sp., and Dib. = Dibothriocephalus spp.). NMDS converged on a three‐dimensional solution with an acceptable stress level
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