Ecosystem effects of partial fish migration in lakes

Abstract

Migration is a widespread phenomenon in many ecosystems. Most often, studies on migration have focused on how migration strategies are dependent on ecological parameters, but little attention has been paid to the top-down effect of migration on ecosystem processes. Cyprinid fish in many European lakes undergo partial migration, where a part of the population leaves the lake and enters streams for the winter. In this study, we model the effect of partial migration by fish on lower trophic levels in a lake ecosystem. Our results suggest that spring phyto-and zooplankton dynamics, including occurrences of clear-water phases, can be related to the timing and magnitude of partial migration of planktivorous fish. From our results we conclude that partial migration can influence the dynamics of lower trophic levels in the ecosystem. Furthermore, we hypothesize that partial migration may affect the stability of alternative stable states and transitions between them.

There and back again: migration in freshwater fishes

“…For example, we may categorize food availability or predation risk as driving causes of migration (e.g., Brönmark et al 2008), whereas decreased competition or change in trophic dynamics may be classified as consequences of migration (e.g., Brodersen et al 2008aBrodersen et al , 2011. As fish have multiple important roles in freshwater ecosystem, the temporal presence-absence and movement between habitats are likely to have multiple effects on their surrounding ecosystems.…”

“…Since migrants, just as any animals, both consume resources and constitute prey to predators, migration may affect the strength of consumer-resource interactions and thus have effects on the trophic interactions in the communities they are migrating to and from, respectively (Brodersen et al 2008a;Post et al 2008). Trophic interactions are very important drivers of the structure and dynamics of aquatic systems and it is hence not only important to consider how environmental circumstances may drive fish migration, but also how fish migration feeds back on and affects the aquatic environment.…”

“…In the alewife example all individuals either migrated or stayed resident, but between-year variation in the timing and proportion of migrating individuals in partially migratory populations has also been predicted to affect the population structure and dynamics of lower trophic levels (Brodersen et al 2008a). In the aforementioned Lake Krankesjön, we have shown that differences in timing of the return migration of the dominant zooplanktivore (roach) to the lake during spring affect the spring peak abundance and size structure of zooplankton (Hansson et al 2007;Brodersen et al 2011).…”

“…Furthermore, fish are major players in aquatic ecosystems, and hence, the synchronized movements of often thousands of individuals between habitats can potentially have profound impacts upon ecosystem dynamics (e.g., Brodersen et al 2008a;Post et al 2008;Brönmark et al 2010). Studies of fish migration can also give us clues as to the forces that shape the evolution of migratory behaviour in animals in general, and highlight the fascinating physiological and life-historical adaptations that have assisted individuals in making these periodic journeys between habitats.…”

Escaping peril: perceived predation risk affects migratory propensity

“…However, to our knowledge, no studies have hitherto used an experimental approach to investigate how changes in perceived predation risk influences seasonal migratory propensity in the wild, providing mechanistic links between predation risk and migration. Our data suggest that predators can impact the migratory dynamics of animals, with potential strong ecosystem consequences [3,29]. Understanding changes in migratory behaviour in response to altered landscapes of predation risk is hereby particularly important, given recent losses in apex predators across the globe via changes in climate, harvesting and pollution [30,31].…”