Competitive effects of fish in structurally simple habitats: perch, invertebrates, and goldeneye in small boreal lakes

Abstract

We determined the associations between Eurasian perch Perca fluviatilis, invertebrates, and common goldeneye Bucephala clangula in boreal lakes. Our aim was to test the hypothesis that perch play a controlling role in small, oligotrophic, acidic, and poorly vegetated boreal lakes, affecting both invertebrate numbers and community structure. In addition, we predicted that perch impact lake usage by goldeneye. In the observational part of our study, we first explored the association between perch, invertebrates and goldeneye (pairs and broods per shore km) in 18 boreal, poorly vegetated lakes. Perch densities were associated negatively with invertebrate abundance and lake usage by goldeneye broods. In the experimental part in three fish-free lakes, we found that upon successful perch introductions, the number and biomass of invertebrates, the proportion of large dytiscids, and lake usage by goldeneye broods significantly decreased. We conclude that perch apparently plays a key role as a predator of invertebrates in boreal lakes with few aquatic macrophytes. It is evident that perch can strongly affect their prey populations and communities, and this predation may have an indirect effect on species, e.g. goldeneye, that consume the same prey.

Breeding in the stable boreal landscape: lake habitat variability drives brood production in the teal (Anas crecca)

“…data). The number of teal broods and ducklings correlates with emerging insects in the lakes (Elmberg et al ., ), and the habitat use of brood‐rearing female teals is particularly associated with small emerging insects (dipterans) (Nummi et al ., ).…”

“…For the current long‐term study, we only included those lakes (7 in total) that had not experienced abrupt changes during the study period (e.g. beaver occupancy, change in fish status due to recovery from acidification; Nummi & Hahtola, ; Suhonen et al ., ; Nummi et al ., ). This is because we wished the lakes to give a general representation of the food situation in the area.…”

Wetland use by brood‐rearing female ducks in a boreal forest landscape: the importance of food and habitat

“…, Nummi et al . ). The association of ducklings with large emerging insects most probably reflects the presence of Trichoptera and Odonata larvae in those very habitats; Goldeneye ducklings frequently prey on these larvae (Eriksson ).…”

Patchiness in food resources drives fish abundances in emergent macrophytes under field and experimental conditions

“…There are usually two alternate hypotheses put forward for patch selection by small-fish under these conditions. Firstly, increased stem density provides more habitat niches for smallfish prey and hence fish abundance will increase with higher stem density (Werner et al, 1983;Gilinsky, 1984;Nummi et al, 2012). An alternate hypothesis is that increased stem density will negatively impact the efficiency of piscivorous predators (large-bodied fish and birds), and as for the first hypothesis, higher stem densities will support higher numbers of small-bodied fish (Heck & Crowder, 1991;Clavero et al, 2005).…”