Freshwater Fishes Freshwater communities Temperate Streams Temperate Lakes

Freshwater Fishes Freshwater communities Temperate Streams Temperate Lakes and Reservoirs Tropical Streams and Lakes

Traditional biotic regions

Temperate streams • Well studied aquatic environments – Highly accessible, experimental manipulations • Highly fluctuating environments – Daily, seasonally, interannually • Very manipulated habitats – Damming, pollution, diversions, channeling, …

Temperate streams – Factors affecting fish distribution • Physical factors – Temperature – Gradient – Flow regime • Chemical Factors – Oxygen levels – p. H

Farmington River La Nivelle River temperature (C) 25 20 15 10 5 0 Feb Apr Jun Aug Oct Dec

Colorado River Flow

Cyprinidae Colorado pikeminow Ptychocheilus lucius

Temperate streams – Factors affecting fish distribution • Biological Factors – Predator-prey interactions – Competitive interactions • Differential resource exploitation • Aggressive behaviors • Biogeographic Factors

Lack of refuge from predation

Temperate streams - Zonation • Mountain zone – Fast flows, Oligotrophic (low productivity), gravel – Salmonidae, Cottidae • Foothill zone – Intermediate flows and productivity – Salmonidae, Cyprinidae, Catostomidae, Percidae, Centrarchidae… • Valley floor zone – Slow flows, Eutrophic (high productivity), soft sediments – Centrarchidae, Cyprinidae, Ictaluridae, Clupeidae…

Mountain zone

Temperate Lakes and Reservoirs • Relatively young environments – A few (reservoirs) to a few thousand (lakes) years + 1500 reservoirs in the USA • Few species exclusively adapted to lakes – Exception in very large & old lakes (Great Lakes and Lake Baikal) • Manipulated habitats – Exotic species, eutrophication, water level changes, pollution

Temperate Lakes & Reservoirs – Factors affecting fish distribution • Physical factors – Temperature • Cold water lakes (Salmonids) • Warm water lakes (Centrarchids, Percids, Esocids) • Two story lakes with Epilimnion & Hipolimnion – Light / Turbidity • Productivity and abundance of planktivorous fishes – Water level fluctuations • Access to spawning sites – Substrate

Temperate Lakes & Reservoirs – Factors affecting fish distribution • Chemical factors – Oxygen levels – p. H • Biological factors – Predation – Competitive interactions

Temperate Lakes & Streams – Zonation. Example: Long lake (MN)

Lake Malawi • Old lake (2 million years) • 600 x 75 km; 785 m depth • ~550 fish species – 546 endemic species – 500 Haplochromine chichlids • Rapid speciation – Simpatric speciation – Microallopatric speciation