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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