Trophic niche similarity among sea trout Salmo trutta in Central Norway investigated using different time-integrated trophic tracers
Permanent lenke
https://hdl.handle.net/10037/11776Dato
2017-11-21Type
Journal articleTidsskriftartikkel
Peer reviewed
Forfatter
Davidsen, Jan Grimsrud; Knudsen, Rune; Power, Michael; Sjursen, Aslak Darre; Rønning, Lars; Hårsaker, Karstein; Næsje, Tor; Arnekleiv, Jo VegarSammendrag
From 2011 to 2013, anadromous brown trout Salmo trutta (213−730 mm, total body
length, LT) were collected during or shortly after their marine feeding migration at 7 different
localities in central Norway. The mean volume of stomach content (%) of marine fish prey eaten
by S. trutta captured in marine waters varied from 34 to 89%. There was a high prevalence
(67−100%) for parasite groups potentially transmitted by marine prey fish (i.e. nematodes, cestodes
and trematodes) at all sampling sites. There was a significant overlap in the signatures of
both δ13C and δ15N in the muscle tissue between the 7 groups of S. trutta; however, individual variation
within groups was large. A strong positive relationship between δ13C and LT indicated sizedependent
niche selection, with smaller individuals feeding less on marine prey and more on
brackish or freshwater invertebrates in the estuary. Short-term gut contents data and trophically
transmitted parasites showed that all size groups were feeding on marine fish. However, an
increased dependence upon marine prey fish by larger S. trutta was indicated by a strong positive
relationship between LT and δ15N. Similarities in S. trutta feeding and time-integrated trophic
tracers (stable isotopes and parasites) across the 7 localities supports the general view that S. trutta
feed within similar marine trophic niches. This similarity in feeding niche requirements may make
S. trutta populations vulnerable to anthropogenic ecosystem perturbations which reduce the
diversity of potential marine prey items.