Aim Our aim was to document geographical patterns of variation in the bodysize
structure of European lake fish assemblages along abiotic gradients, and
any differences in fish assemblage structure. We hypothesized that patterns in
the body-size structure of entire lake fish assemblages are primarily temperature
driven and consistent with the dominant pattern of the temperature–size
rule, which suggests a decrease in adult body size with increasing developmental
temperature for many ectothermic species.
Location 356 European lakes.
Methods Variation in the body-size structure of fish assemblages was explored
on a continental scale along gradients of temperature, morphometry, productivity
and fish assemblage structure for 356 European lakes. The mean fish
assemblage body-size and individual body-size distributions were selected as
size metrics. Separate analyses were conducted for lakes located within five ecoregion
subsets (Borealic Uplands/Tundra, FennoScandian Shield, Central
Plains, Western Plains and Western Highlands) and for lakes with different
functional fish classifications (cold-, cool- and warmwater fish assemblages).
Results Geographical patterns of variation in the body-size structure of European
lake fish assemblages could be clearly discerned along a temperature gradient
for both the continental dataset (356 lakes) and the smaller geographical
(ecoregion) subsets. We found systematic changes in fish assemblage body-size
structure across temperature gradients in correspondence with the dominant
thermal fish guild. The majority of the lakes, mainly located in the warmer European
lowlands, were dominated by eurythermic cool- and warmwater fish assemblages,
with smaller sized individuals characterized by linear individual body-size
distributions. Lakes located in colder regions and dominated by stenothermic
coldwater salmonids with larger sized individuals were characterized by unimodal
or bimodal size distributions. The mean body size of cold-, cool- and warmwater
fish assemblages changed uniformly along the temperature gradient.
Main conclusions Patterns of variation in the body-size structure of European
lake fish assemblages are consistent with the temperature–size rule. Temperature
modifies fish assemblage size structure uniformly within the thermal
fish guilds and in different ecoregions. Furthermore, our results indicate an
increasing predictive power of temperature to explain variability in body-size
structure when moving from warmer to colder geographical regions.
Keywords
Body size, European lakes, freshwater fish, functional classification, individual
body-size distribution, macroecology, multimesh gillnet, temperature gradient,
temperature–size rule, thermal guild.
