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Community EcologyNatural enemies -- Predators
1. How do predatory invertebrates impact theirprey populations?
2. Is Bythotrephesa typical invertebrate predator?
3. Can bluegill influence the growth rate of bass?
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Vertebrates Invertebrates
Find prey by vibration orchemical cues
Tend to select smaller
prey
:www.cnr.vt.edu/efish/families/ bluegill.htmlhttp://www.potomacriver.org/images/biology/Leptodorabig.jpg
dnr.metrokc.gov/wlr/waterres/ lakes/biolake.htm
www.zi.biologie.uni-muenchen.de/ .../feinstruktur/em.htm
www.fs.fed.us/wcnf/fishing/ lakes/lake07.htm
Use vision to find prey
Tend to select larger prey
Predators in Lakes
http://www.cnr.vt.edu/efish/families/bluegill.htmlhttp://www.cnr.vt.edu/efish/families/bluegill.htmlhttp://dnr.metrokc.gov/wlr/waterres/lakes/biolake.htmhttp://dnr.metrokc.gov/wlr/waterres/lakes/biolake.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.fs.fed.us/wcnf/fishing/lakes/lake07.htmhttp://www.fs.fed.us/wcnf/fishing/lakes/lake07.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://dnr.metrokc.gov/wlr/waterres/lakes/biolake.htmhttp://www.cnr.vt.edu/efish/families/bluegill.htmlhttp://dnr.metrokc.gov/wlr/waterres/lakes/epimale.jpg -
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Predatory Vertebrates
Planktivores
Piscivores
Larval and adultsalamanders
Birds
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Notonecta--backswimmer
Predatory Invertebrates Insects
Chaoborusphantom midge
Dyticidbeetle larva
www.zi.biologie.uni-muenchen.de/ .../feinstruktur/em.htm
http://www.fhsu.edu/biology/thomasson/AquaticInsects/HerlOdonata/Herl.htm
Dragonflies
www.biol.lu.se/funkmorf/ vision/dan/prey.html
http://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.biol.lu.se/funkmorf/vision/dan/prey.htmlhttp://www.biol.lu.se/funkmorf/vision/dan/prey.htmlhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htmhttp://www.zi.biologie.uni-muenchen.de/institute/zi/abtlgn/feinstruktur/em.htm -
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Predatory Invertebrates
Leptodora
cladocerans andcopepods
Epichura
http://www.microscopy-uk.org.uk/mag/wimsmall/extra/rotif2.html
http://dnr.metrokc.gov/wlr/waterres/lakes/epimale.jpg -
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Which type of predator will dominate in aparticular habitat?
Complex question, depends onabiotic conditions temp, oxygen, water chem
competition among predatorspredators of the predators
Already talked about predation by vertebrates,will focus now on predation by invertebrates
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When planktivorous fish are abundant, predatoryinvertebrates are often excluded
.from the epilimnion
or the entire lake
Predatory invertebrates have to balance foodacquisition with avoiding predation
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Most predatory invertebrates that feed in theplankton tend to select prey that are smaller thanthey are
Or juveniles of largerspecies (e.g., nauplii,juvenile Daphnia)
So they select smallspecies (e.g., Bosmina,
Ceriodaphnia, Rotifers)
http://www.microscopyu.com/moviegallery/pondscum/crustacean/nauplius/
http://images.google.com/imgres?imgurl=www.vvm.com/~jevans/cerio1.gif&imgrefurl=http://www.vvm.com/~jevans/clad10.html&h=175&w=200&prev=/images%3Fq%3DCeriodaphnia%26start%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DN -
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Daphniais the prey
Why do predatory invertebrates select smallerprey items?
Chaoborushas swim bladderssit and wait predator
Gape limitation again...
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Encounter rate between predator and preygoes up linearly with Daphniasize
becauseChaoborus
detect prey bytheir wake.
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But handing time goes up exponentially with size
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The relationship between encounter rate and strike efficiencysuggest that medium-size prey are the optimal diet choice
Encounter rate
Strike efficiency
Vulnerability
l
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In general...
Just like fish, predatory invertebrates will encounter bigzooplankton more frequently.
Very young fish will be gape limited, so will avoid bigzooplankton. But, most planktivorous fish are not gape-limitedso select the largest individuals.
Fish are size-selective and prefer larger prey items.
But, many predatory invertebrates cannot handle the largestzooplankton, so select for small or intermediate sized animals
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How do predatory invertebrates find their prey?
1) Wakes
Different sized animals have different sized wakes
Many predators cue into this movement. They areattracted to small wakes, repelled by larger wakes
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Many copepods are covered withchemosensory pits, can smell their prey
How do these predators find their prey?
2) Chemical cues
http://dnr.metrokc.gov/wlr/waterres/lakes/epimale.jpg -
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Many examples about how invertebrate predatorseat smaller things and therefore influencecommunity structure.
But, there are cases where predatory invertebrates
dont follow the general rule...
B h h i N h A i (i d d
http://dnr.metrokc.gov/wlr/waterres/lakes/epimale.jpg -
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Daphnia pulicara(large bodied)
Daphnia galeata mendotae(slightly smaller than D.p.)Daphnia retrocurva(small)
Bythotrephesexotic to North America (invadedin mid 1980s), but native to Europe.
Prior to invasion of Lake Michigan, offshore waterhad:
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After Bythotrephesinvaded, all three populationscollapsed but only D.galeata(the medium sized
species) recovered and remained in the plankton.
Could Bythotrepheshave done this?
Time
Ab
undance(#/L)
D. pulicariaD. retrocurva
D. galeata
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Schulz and Yurista 1999
Offered Daphniaof
different sizes toBythotrephes
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Bythotrepheshas arms.
As with Chaoborus, encounter rate went up withlarger species, but Bythotrephesdoes not showthe same decline in capture efficiency.
Ad lt B th t h f l d h iid
http://nsgl.gso.uri.edu/source/fbyo.gif -
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Why did the medium sized species survive?unknown, probably DVM
Adult Bythotrephes prefer large daphniids(D. pulicaria)
Juvenile Bythotrephes eat the small daphniids
(D. retrocurva)
M lti l d t
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Multiple predators
Daphnia
Planktivorous Fish
Chaoborus
The presence ofmore than one
predator speciescan influence thedynamics of boththe predatorsand the prey
M lti l d t
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Multiple predators
Two ways that the presence of a second predator species caninfluence the amount of prey the first species can consume
1. Changing the abundance of other predator species
When fish eat Chaoborus, there are fewerChaoborus
2. Changing the behavior of the other predator species(activity levels, habitat use, direct interference, etc.)
Chaoborusavoids the surface waters whenbluegill are present
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How multiple predators influence the preydepends on the nature of the predator-predator
interaction
e.g. if fish eat Chaoborus, then Chaoborusis
less of a threat to Daphnia
But, if the presence of fish changes the
behavior of Daphnia, the Daphniamayexperience a higher risk of predation byChaoborus
Piscivoryhttps://reader009.{domain}/reader009/html5/0427/5ae207e3c7a09/5ae207fdb3d08.jpg
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Piscivory
J. Forney Oneida Lake, NY
Perch eat Daphnia,
benthic invertebrates,
smaller perch
Walleye eat perch
(Yellow perch abundance)
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Olson and colleagues, 1995, 1997Complex Interactions:
Bluegill (Lepomis macrochirus)
Largemouth bass (Micropterus salmoides)www.museum.state.il.us/.../ largemouth_black_bass.html
www.cnr.vt.edu/efish/families/ bluegill.html
http://www.museum.state.il.us/RiverWeb/harvesting/harvest/fish/species/largemouth_black_bass.htmlhttp://www.museum.state.il.us/RiverWeb/harvesting/harvest/fish/species/largemouth_black_bass.htmlhttp://www.cnr.vt.edu/efish/families/bluegill.htmlhttp://www.cnr.vt.edu/efish/families/bluegill.htmlhttp://www.museum.state.il.us/RiverWeb/harvesting/harvest/fish/species/largemouth_black_bass.html -
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Small bluegill (20-75 mm) are restricted by predators (bass) to
the protection of the littoral zone vegetation. They feed on
benthic invertebrates.
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Above 75 mm, the bass are gape limited, so the bluegill can
feed in the open water where they have access to more
zooplankton.
Th l bl ill l b k d f th b t
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The larger bluegill can also go back and forth between
the open water and littoral zone.
P d t i t ti
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Predatorprey interaction
Littoral zone provides a refuge from predation for the small
bluegill and gape limitation provides a refuge for large
bluegill
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But juvenile bass also stay (and feed) in the littoral zone
making the bluegill and bass potential competitors
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The longer it takes the bass to grow, thelonger it takes the bass to get to a size where
they are big enough to eat bluegill
If bluegill are better competitors than bass,then it will take the juvenile bass longer to grow
Ol t l 1995
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High Bluegill 800 bluegill + 70 Bass = 870
Olson et al. 1995http://www.kbs.msu.edu/Research_Facilities/Pond_Lab/Overview.htm
Pond divided into 8 sections 4 treatments
Target 50 bluegill + 70 Bass = 120
Bass 50 bluegill + 220 Bass = 270
Low Bluegill 200 bluegill + 70 Bass = 270
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(120)
(270)
(270)
(870)
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Concepts to know
How does predation by invertebrate predators impact thesize-structure of zooplankton assemblages? How doesthis differ from predation by fish?
Why is Bythotrephesnot the typical predatory invertebrate?
How do multiple predator interactions change the risk
experiences by prey?
How do bluegill and bass interact?
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Practice question
Oneida Lake is a large (surface area = 207 km2) lake in upstate New York.Although the lake reaches depths of up to 12m, it does not stratify
thermally because it has a 33 km long fetch in the direction of theprevailing winds. The major piscivore in Oneida Lake is the walleye(Stizostedion vitreum) and the major planktivore is yellow perch (Percaflavescens). For the last several years, the shoreline and several of thesmall islands of Oneida Lake have become increasingly populated by the
Double-Crested Cormorant (Phalacrocorax auritus). This diving water birdis extremely good at catching fish and preferentially feeds on walleye.Using the reasoning of the Trophic Cascade Theory, predict how algalabundance should respond as the cormorant population increases. Makesure your answer includes an explanation of the mechanisms leading to this
di t d i l l b d
Double-Crested Cormorantwww.npwrc.usgs.gov/resource/ tools/waterfwl/cormornt.htm
http://www.npwrc.usgs.gov/resource/tools/waterfwl/cormornt.htmhttp://www.npwrc.usgs.gov/resource/tools/waterfwl/cormornt.htm