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Flexible Summer Habitat Selection by Wild, Allopatric Brown Trout in Lotic Environments
Author(s) -
Heggenes Jan
Publication year - 2002
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(2002)131<0287:fshsbw>2.0.co;2
Subject(s) - allopatric speciation , river ecosystem , habitat , trout , selection (genetic algorithm) , ecology , fishery , biology , fish <actinopterygii> , computer science , artificial intelligence , demography , sociology , population
Spatial and temporal hydraulic heterogeneity influence distributional patterns of species in streams. Ecological theory suggests flexible habitat selection strategies are favored in such unstable environments. The effects of varying hydraulic conditions on habitat selection by brown trout Salmo trutta in summer were studied in eight streams in Norway and Scotland. At normal summer flows, brown trout averaging 16 cm total length (SD = ±5 cm, range = 3‐43 cm) were selective in habitat use. The selection window was relatively narrow for focal water velocity (mean = 14 cm/s, median = 10 cm/s, 60.1% of observations ≤14 cm/s). Trout favored slower flowing pool areas, but selection ranges were wide (mean water column velocity = 24 ± 21 cm/s, range = 0‐142 cm/s; mean depth = 69 ± 29 cm, range = 9‐305 cm). Larger fish used deeper habitats; other variables did not correlate with size. Great overlaps in spatial niche used by the studied size‐classes of trout indicated versatility in habitat selection (e.g., in response to varying hydraulic conditions). Considerable within and among stream variation in habitat selection, largely depending on habitat availabilities, was most pronounced for water depth (mean range = 40 ± 24 cm to 109 ± 48 cm). Focal water velocities, an exception that remained remarkably stable across streams, may be explained by the larger spatial scale in the distributional pattern of depths, compared with a micromosaic in water velocities. Temporal variation related to changes in water flows produced almost complete habitat shifts in mean water column velocity (from 2 to 33 cm/s, SD = 4‐20 cm/s) and even focal water velocities (from 1 ± 3 cm/s to 17 ± 10 cm/s), whereas selection of water depths remained more stable. The results suggest in situ hydraulic variability affects fish behavior. The flexibility in behavioral responses also suggests the use of habitat and foraging models assuming similar habitat use at all streamflows may be flawed.