Differences in trophic niches and life-history traits between brook trout and brown trout in alpine lake food webs

Abstract

Trophic ecology of lacustrine salmonid populations is well-documented in North America and northern Europe, highlighting their role in aquatic ecosystems. However, there is a notable gap in comparative studies on the trophic niches and life-history traits of salmonids in Iberian alpine lakes, which are increasingly impacted by introduced fishes. We compared the trophic ecology and life-history traits of brook trout ( Salvelinus fontinalis ) and brown trout ( Salmo trutta ) in two alpine lakes of central Spain, providing insights into their ecological roles and potential responses to environmental pressures. Compared to brown trout, brook trout displayed a broader dietary niche (based on isotopes and stomach contents), higher reliance on terrestrial food resources, higher δ 13 C values and higher trophic position. Thus, the higher trophic position of top predator salmonids suggests a slightly longer food chain in the lake with brook trout. Brook trout showed a higher trophic plasticity indicated by an ontogenetic dietary shift from zooplanktivory to more generalist foraging on terrestrial prey. Brook trout displayed life-history traits such as early maturation, which likely facilitate successful establishment in alpine lakes. Our study suggests that the trophic plasticity and adaptive life-history traits likely support the successful establishment of non-native salmonids in alpine lake food webs.

Bibliographic Information