Fish Conservation and Management - UBC Faculty of...
Transcript of Fish Conservation and Management - UBC Faculty of...
![Page 1: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/1.jpg)
Fish Conservation and Management
CONS 486
Trophic pyramids, food webs, and trophic cascades… oh my!
Ross Chapter 2, Diana Chapter 1
![Page 2: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/2.jpg)
Trophic interactions
• Limnological classification review
• Trophic pyramids and productivity
– Food webs
• Trophic cascades
– Examples
![Page 3: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/3.jpg)
Major theme: Linking science to conservation & management
• Harvest regulations
• Managing fisheries & habitats
• Protecting populations & habitats
• Restoring populations & habitats
• Fisheries exploitation data
• Applied life history data
• Human dimensions: socio-economic data
• Physiology
• Behaviour
• Population ecology
• Ecosystem ecology
• Habitat data (limnology, oceanography)
• Life historyBasic science
Applied science
ManagementConservation
![Page 4: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/4.jpg)
Introduction
• To conserve fish, it’s not enough to only understand how individual species may compete or prey upon
– Must also take a larger view and consider how communities (groups of species) interact
• Trophic level interactions can differ among different aquatic systems
– E.g., epilimnetic vs hypolimnetic systems
– Low order vs high order stream systems, etc.
• Very exciting review of limnological terms and locations!
![Page 5: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/5.jpg)
Lake Zonation
Cole 1983
or Pelagic zone
![Page 6: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/6.jpg)
Lake zonation: Littoral zone• Shoreline areas extend to edge of rooted
vegetation
–High erosion due to wave and ice action therefore relatively coarse sediments
• Subject to fluctuating temperatures, can be very warm in summer
6
Open-water limnetic zone
Deep-water profundal zone
![Page 7: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/7.jpg)
Lake zonation: Littoral zone• Well lit, high plant growth, large inputs of LW
and leaf litter
–Due to wave action and gravity, eventually this detritus moves out of littoral zone
• High production of aquatic invertebrates on plants and substrate
• Macrophytes, rocks and large wood create good rearing areas for fish– Predominantly perciformes and some cypriniformes
7
![Page 8: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/8.jpg)
Open-water limnetic zone
Deep-water profundal zone
Lake zonation: Limnetic zone• Open water, little influence of large wood or other
structures
• Plankton zone (phyto and zoo)
– Lots of sunlight, photosynthesis
– O2 production
• No macrophytes
• Rearing area for planktivorous fish
– Kokanee/sockeye fry, whitefish
8
![Page 9: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/9.jpg)
De
pthTemperature
Epilimnion – homogeneous and warm
Metalimnion - thermocline
Hypolimnion –homogeneous and cool
![Page 10: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/10.jpg)
Lake zonation: Profundal zone• Includes benthic zone (ecological region along substrate)
• Bottom sediments, soft and muddy, very little physical structure– Most decomposition occurs here, sediments can get anoxic
• Supports inverts which often tolerate low oxygen
• LW, litter or sediment from riparian/hillslopes settle here
• If O2 is adequate, spawning habitat for bottom dwelling fish – Suckers, burbot, lake trout and other salmonids
10
Open-water limnetic zone
Deep-water profundal zone
![Page 11: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/11.jpg)
Lake trophic (productivity) status• Two fundamental lake types at either end of the
ageing and productivity spectrum
– Oligotrophic and eutrophic
EutrophicOligotrophic
![Page 12: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/12.jpg)
Oligotrophic lakes are:• Young and deep
• Nutrient input from watershed is low
• Small littoral area with few plants
• Low levels of detritus and decomposition
• Abundant oxygen throughout entire lake
• Low phyto, zooplankton and fish production
• Small epilimnion relative to hypolimnion
• Hypolimnion well oxygenated all year therefore good habitat for some fish (salmon!)
![Page 13: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/13.jpg)
Oligotrophic lakes
![Page 14: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/14.jpg)
Eutrophic lakes are:• Old and shallow
• Nutrient rich
• High phytoplankton and plants
• Large littoral and epilimnion
– Contributes to abundant warm water fish
• Hypolimnion small and anoxic/hypoxic
– Poor salmonid habitat
![Page 15: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/15.jpg)
Eutrophic lakes
![Page 16: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/16.jpg)
Trophic pyramids• Trophic pyramids: display food structure of an
ecosystem
– Illustrates the productivity and types of organisms in consecutive trophic levels
1st trophic level: producer
2nd trophic level: primary consumer
3rd trophic level: secondary consumer
4th trophic level: tertiary consumer
5th trophic level: quaternary consumer
![Page 17: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/17.jpg)
Trophic pyramids: Lakes• Different productivity pyramids for a typical lake within the
two stratified layers and in the littoral zone in both eutrophic and oligotrophic lake
– Note different base of pyramid yet piscivores rule!
Diana Figures 1.2 and 1.3
![Page 18: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/18.jpg)
Trophic pyramids: Streams• River continuum concept: continuum between
narrow low order streams and wide high order streams
![Page 19: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/19.jpg)
Pyramids vs webs• Trophic pyramids provide a simple way to examine
energy flow in a system
– But do not reveal the typical complexities and multiple energy pathways that exist…
• Food webs!
VS
![Page 20: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/20.jpg)
Pelagicor
Limneticareas of
lakes
Profundal and
littoral(and
streams)
General aquatic food web
![Page 21: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/21.jpg)
General aquatic food web
• Food webs
–Arrows show energy flow
–Complexities arise because the various sub-systems (e.g. epilimnion, hypolimnion, littoral) are linked in space so energy moves between them
• E.g., in a lake, disparate areas like pelagic and littoral areas get linked by detrital, bacterial and nutrient cycles
–Especially once lakes start to mix
![Page 22: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/22.jpg)
Mar
k D
avid
Th
om
pso
n
Aquatic and terrestrial webs are linked
![Page 23: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/23.jpg)
Trophic cascades• Predators can cause changes to their prey
populations
– BUT predators can cause changes to populations in trophic levels beyond those they feed on
• In these instances, top predators are considered a keystone species
– Their presence affects total trophic structure
![Page 24: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/24.jpg)
Trophic cascades• Trophic cascades characterized by relatively simple
food webs
– The more “chain-like”, the more likely it is to occur
• Imagine a scenario with a single piscivore, a few panktivores, herbivores, and phytoplankton
![Page 25: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/25.jpg)
Herbivorebiomass
Piscivore biomass
Phytoplanktonbiomass
Planktivorebiomass
piscivore
herbivores
planktivores
phytoplankton
![Page 26: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/26.jpg)
Trophic cascades• Early 1900s, Alaskan coast had lush kelp communities with
thriving otter, seal and bald eagle pops
• Hunting reduced mammal pops and they had few kelp beds
• Sea otters legally protected 1911
– Habitat they occupied began to grow lush kelp communities
• Otters prey on sea urchins which graze on the kelp,
• Thus, humans kept otter populations down, which led to high urchin populations, which led to low kelp populations
![Page 27: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/27.jpg)
otterbiomass
human Predation intensity
kelpbiomass
sea urchinbiomass
humans
otters
sea urchins
Kelp
![Page 28: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/28.jpg)
Estes et al. 2011 Science
Absent Present
• Long Lake (Michigan) with largemouth bass present (right) and experimentally removed (left)
• Bass decrease zooplantivorous fishes
– zooplankton have less predation & increase in abundance
– more zooplankton consumes phytoplankton (incl algae)
• Less algae/phytoplankton means clearer water
Trophic cascades: experimental results
![Page 29: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/29.jpg)
Applying Trophic-cascades: ‘Bio-manipulation’
• University of Wisconsin, Lake Mendota, Madison Wisconsin
• Nutrient run-off leading to algal bloom
creating odor and O2 issues in the lake
• Added 300 adult bass (piscivores)
• 1 year later other fishes (minnows, zooplanktivores) eliminated!
• Zooplankton biomass doubled, phytoplankton biomass halved
– Water clarity improved and odor problem solved
![Page 30: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/30.jpg)
Trophic Cascades can occur in large systems
• Lake Michigan started salmon hatchery programs in 1970s & 80s
• By mid-1980s the main pelagic prey of adult salmon (alewife) had reached record low numbers
– Simultaneous to this was a large increase in daphnia (a large bodied zooplankton)
– Other plankton abundances remained unchangedalewife
daphnia
![Page 31: Fish Conservation and Management - UBC Faculty of Forestryfaculty.forestry.ubc.ca/hinch/486/2016/lectures 2016... · 2016-01-15 · Fish Conservation and Management CONS 486 Trophic](https://reader033.fdocuments.in/reader033/viewer/2022042021/5e781230d17b3771da39b7ac/html5/thumbnails/31.jpg)
Top-down vs bottom-up
Trophic cascades illustrate ‘top-down’ influences:
Predation controls abundance at each successive lower trophic level
A ‘bottom-up’ phenomenon would involve lower trophic levels influencing successively higher ones (eg. via nutrient or food availability – can be largely affected by stochastic effects of climate)
‘Top-down’ patterns are largely affected by biotic processes whereas ‘Bottom-up’ patterns by abiotic processes.
Both processes can occur in aquatic ecosystems
– Bottom-up often influences lower trophic levels
– Top-down often influences higher trophic levels