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 –pH

FebAprJunAugOctDec River temperature (C) Farmington River La Nivelle River

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 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 –pH 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