A nice looking lake, right?

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1 A nice looking lake, right? Wrong! It s a reservoir (an artificial lake ). This is Bull Shoals Lake aka Reservoir at the Missouri-Arkansas border. A reservoir is not a lake some key and fundamental differences.

2 Large wood - but where did it come from?

3 Its part of the forest that was flooded for recreational fishing

4 Submerged tree

5 Bull Shoals Dam Missouri/Arkansas Bull Shoals Dam built in 1951 dams the White River and forms the bottom-most of four artificial lakes. Dam built primarily for flood control but also used for power generation and recreational activities. From its completion until 2009, it is estimated that the dam has prevented about $225.5 million in flood damages. Bulls Shoals makes up 182 km²

6 Home to different types of aquatic fauna

7 Very popular for recreation, and.

8 FISHING! Focus of a several largemouth bass stocking programs and fishing competitions State record bass 13 pounds! Marvin Bushong

9 Fish Conservation and Management CONS 486 Reservoir ecosystems

10 Reservoir ecosystems Reservoir background Longitudinal gradients Reservoirs vs lakes Trophic upsurge/depression

11 Major theme: Linking science to conservation & management Physiology Behaviour Population ecology Ecosystem ecology Habitat data (limnology, oceanography) Life history Basic science Applied science Fisheries exploitation data Applied life history data Human dimensions: socioeconomic data Protecting populations & habitats Restoring populations & habitats Conservation Management Harvest regulations Managing fisheries & habitats

12 Introduction We ve talked mostly about stream and lake systems But guess what, there s more! Most reservoirs in N.A. < years old Created primarily for water storage E.g., flood control, domestic water supply, irrigation, navigation, hydroelectric power Reservoirs used for recreational purposes (e.g. fishing, boating) Sport fishes and their prey have been introduced Now majority of all US freshwater fishing occurs in reservoirs!

13 There are more reservoirs in the US than Canada - Why? - almost all of Canada was glaciated years ago - glacial retreat created an abundance of lakes

14 There are more reservoirs in southern and western US why? Northern US was more glaciated therefore has more lakes than southern US What about the west? Location of reservoirs and lakes

15 In the west (mostly), evaporation exceeds rainfall Thornton et al. 1990

16 Re-cap There are more reservoirs in the US than Canada Greater demand for water and lack of natural lakes in much of the central and southern parts of the US The last glaciation created most of the lakes in Canada Only extended into the northern US states Water demand is high in western US to support agriculture and large cities Also, where evaporation exceeds rainfall, which is where so many of the reservoirs are located

17 Number of large dams Dam it! Canada is one of the world s largest dam builders # large dams in Canada (> 15 m height) is hydroelectric power generation (596 dams) -multi-purposes (86 dams) -tailings (82 dams) -water supply (57 dams) -irrigation (51 dams) -flood control (19 dams) -recreation (7 dams) -other purposes (35 dams) QUE. ONT. B.C. NFLD. ALB. SSK. MAN. N.S. N.B. N.W.T. Y.T. P.E.I. Canadian Dam Association's register of dams (2003)

18 Longitudinal gradients Reservoirs act like a river/lake hybrid Due to shape and inflow characteristics: elongated, dendritic Three zones riverine, transitional, lacustrine

19 Longitudinal gradients: Riverine zone Riverine zone: the reservoir is fairly narrow, shallow High flow rates High suspended solids High nutrients Low light penetration Energy derived from allochthonous means No thermal stratification

20 Longitudinal gradients: Lacustrine zone Lacustrine zone: the reservoir is wide and usually deep Low flow rates Low suspended solids Low nutrients High light penetration Sometimes has thermal stratification Energy derived from autochthonous means Oligotrophic reservoirs will have high oxygen in hypolimnion Eutrophic reservoirs will not

21 Longitudinal gradients: Transition Zone Transition zone: all characteristics are intermediate relative to riverine and lacustrine Constant addition of nutrients, organic matter and light penetration Constant export of production Thus highest production of phyto/zooplankton in this zone Nutrients & food resources end up here Little stratification: so whole zone is involved in this production

22 Drainage basin characteristics: lake vs reservoir Shoreline Irregularity Reservoirs have high shoreline irregularity, and is dendritic as a result of river tributaries being flooded RESERVOIR LAKE

23 RESERVOIR Drainage Basin size Reservoirs have large drainage basin sizes relative to reservoir area and are always situated at outflow of watersheds; most lakes have small drainage basins relative to their size LAKE

24 RESERVOIR Inflows Reservoirs have inflows from one or two inputs from high order streams; lakes have inflows from several small low order streams LAKE

25 Outflows Reservoir outflows are human controlled and water can be released from any thermal strata; lakes are seasonally regulated and just from the epilimnion LAKE RESERVOIR

26 Biological aspects Phyto/Zooplankton - Reservoirs have longitudinal gradient; lakes have depth gradient Benthos Reservoirs have low biomass (especially with drawdowns in littoral and sedimentation in profundal); lakes have higher biomass Natural fish community Reservoirs have low diversity and colonizer (rapid r ) riverine species which are not usually recreationally desirable; lakes have higher diversity of species RESERVOIR LAKE

27 Trophic upsurge and depression Fish production often extremely high early after reservoir operation starts (upsurge) But never maintained at this level (depression) Trophic upsurge - food and space resources become super abundant

28 Why trophic upsurge? Trophic upsurge occurs because: It s a new environment so competition is minimal Newly inundated areas release their surface nutrients which leads to a boom in phyto/zooplankton Most reservoirs do not remove vegetation from inundated areas and these provide: Benthic structure (refuges, spawning areas) and Epiphytic inverts thrive on the vegetation (food for fish) Sounds great

29 What could possibly go wrong? Trophic depression Occurs 5-20 years after startup Nutrient input decreases and the vegetation breaks down Competition for limited food and space intensifies Sedimentation of spawning areas can also occur Standard water withdrawals prevent littoral area from developing Fish habitat changes from benthic dominated to pelagic dominated; only structure would be rocks

30 Production Benthic dominated fish habitat Pelagic dominated fish habitat Vegetation Fish Nutrients Zooplankton Trophic upsurge Reservoir age Trophic depression

31 We ll dive into Ocean ecosystems! Coming up next