Food borne parasites as indicators of trophic segregation between Arctic charr and brown trout

Abstract

The habitat and diet choice and the infection (prevalence and abundance) of trophically transmitted parasites were compared in Arctic charr and brown trout living sympatrically in two lakes in northern Norway. Arctic charr were found in all main lake habitats, whereas the brown trout were almost exclusively found in the littoral zone. In both lakes the parasite fauna reflected the niche segregation between trout and charr. Surface insects were most common in the diet of trout, but transmit few parasites, and accordingly the brown trout had a relatively low diversity and abundance of parasites. Parasites transmitted by benthic prey such as Gammarus and insect larva, were common in both salmonid host species. Copepod transmitted parasites were much more common in Arctic charr, as brown trout did not include zooplankton in their diets. Parasite species that may use small fish as transport hosts, were far more abundant in piscivorous fish, especially brown trout. The seasonal dynamics in parasite infection were also consistent with the developments in the diet throughout the year. The study demonstrates that the structure of parasite communities of charr and the trout is highly dependent on shifts in habitat and diet of their hosts both on an annual base and through the ontogeny, in addition to the observed niche segregation between the two salmonid species.

Winter ecology of Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) in a subarctic lake, Norway

“…For large-sized fish the diet overlap is even lower as the charr predominantly feed on G. lacustris, whereas the trout mainly prey upon small Arctic charr. Gammarus is an important macroinvertebrate prey for many fish species (MacNeil et al 1999), but it is also an important intermediate host for several parasite species, including the cestode Cyathocephalus truncatus that can parasitize both Arctic charr and brown trout (Amundsen et al 2003;Knudsen et al 2008). This cestode can manipulate the behaviour of their Gammarus hosts in order to increase transmission rates (Knudsen et al 2001).…”

Ontogenetic dynamics of infection with Diphyllobothrium spp. cestodes in sympatric Arctic charr Salvelinus alpinus (L.) and brown trout Salmo trutta L.

“…Based on general dietary niches of charr and trout in sympatry (Nilsson, 1963;Langeland et al, 1991;Knudsen et al, 2008;Eloranta et al, 2013), we expected the transmission routes and the resulting infection patterns of two Diphyllobothrium species to differ between the fish species. The observed differences in Diphyllobothrium infections largely confirmed the expected copepod transmission route in charr and the piscivorous transmission route in trout.…”

“…This niche segregation may be reflected in the parasite communities of these two salmonids. Knudsen et al (2008) found that charr had more copepod-transmitted parasites than did trout and related this to charr feeding more often on zooplankton compared to trout.…”

“…Can this also drive differences in the loads of parasites transmitted through the food web? The use of parasites as markers to elucidate aspects of host ecology is widely recognized (Williams et al, 1992;Knudsen et al, 2004Knudsen et al, , 2008Hechinger et al, 2007;Valtonen et al, 2010). Trophically transmitted parasites are valuable tracers of long-term patterns in foraging and are useful indicators for niche segregation at an individual or population level (Knudsen et al, 2014).…”

“…Bérubé & Curtis, 1986;Frandsen et al, 1989;Knudsen et al, 2008). These parasites, which are transmitted to fish when they feed on copepods, become adults in piscivorous birds and, for D. dendriticum, some mammals (Halvorsen, 1970).…”