Instructor Lecture 5

7/31/2019 Instructor Lecture 5

1/22

Diversity of Aquatic OrganismsVertebrates and Plants

1. How are fish classified?

2. Why are planktivores size-selective?

3. How many mating types are there in bluegill?


2/22

What is a fish?

Phylum Chordata, Subphylum Vertebrata

Lives in water

Possess gills that are used throughout life

Has fins


3/22

Major Classes of Living Freshwater Fishes

Jawless fishes lamprey

Sharks and Rays some rays live in tropical rivers

Class Agnatha

(Cephalaspidomorphi)

Class Chondrichthyes

Potamotrygon

www.tcp-ip.or.jp/~y-miura/ fws/Esyurui.html

Lampetra richardsoni

(western brook lamprey)www.orst.edu/instruct/fw316/ markle/fishimages.html
http://www.tcp-ip.or.jp/~y-miura/fws/Esyurui.htmlhttp://www.orst.edu/instruct/fw316/markle/fishimages.htmlhttp://www.orst.edu/instruct/fw316/markle/fishimages.htmlhttp://www.tcp-ip.or.jp/~y-miura/fws/Esyurui.htmlhttp://www.tcp-ip.or.jp/~y-miura/fws/Esyurui.htmlhttp://www.tcp-ip.or.jp/~y-miura/fws/Esyurui.htmlhttp://www.tcp-ip.or.jp/~y-miura/fws/Esyurui.htmlhttp://www.tcp-ip.or.jp/~y-miura/fws/Esyurui.html


4/22

Major Groups of Living Freshwater Fishes

2 classes of Bony Fishes (Osteichthyes)

Class Sarcopterygii lungfishes

Class Actinopterygii ray-fins

Lepidosiren

(South American Lungfish)

http://www.ucmp.berkeley.edu/vertebrates/sarco/dipnoi.html

Perca flavescens

(Yellow Perch)

www.cnr.vt.edu/efish/ families/yperch.html
http://www.cnr.vt.edu/efish/families/yperch.htmlhttp://www.cnr.vt.edu/efish/families/yperch.htmlhttp://www.ucmp.berkeley.edu/vertebrates/sarco/lungfish1.jpg


5/22

Spiny rayed fish vs. soft rayed fish


6/22

Order Perciformes

Contains over 9,200 species

Largest order of vertebrates

Very diverse group, but most are

predators

Sunfish

Bass

Yellow Perch


7/22

East African Cichlids

www.reshafim.org.il/fishfarm/ lake_victoria.htm

Haplochromis obliquidens

badmanstropicalfish.com/ afcichlids.html

Over 300 endemic

species describedfrom Lake Victoria,

500 from Lake Malawi

and 160 from Lake

Tanganyika

(Order Perciformes)
http://www.reshafim.org.il/fishfarm/lake_victoria.htmhttp://badmanstropicalfish.com/afcichlids.htmlhttp://badmanstropicalfish.com/afcichlids.htmlhttp://www.reshafim.org.il/fishfarm/lake_victoria.htm


8/22

Order Cypriniformes

Family Cyprinidae (minnows and carps)

About 286 species of cyprinids, in N. America, over 40% areshiners

Emerald Shiner(Notropis atherinoides)www.dnr.state.oh.us/wildlife/ fishing/fishid/remainder.htm
http://www.dnr.state.oh.us/wildlife/fishing/fishid/remainder.htmhttp://www.dnr.state.oh.us/wildlife/fishing/fishid/remainder.htm


9/22

Size, shape, gape and position of the mouth often reflect

diet and habitat

Planktivore eats zooplankton

Piscivore eats fish

Detritivore eats organic material from sediments

Herbivore eats plants

Benthivore eats food on the bottom

Omnivore eats plants and animals

stewartsguideservice.com/ mixedbagarchive.htm

www.dbs.nus.edu.sg/.../ catfish/catfish.htm
http://stewartsguideservice.com/mixedbagarchive.htmhttp://stewartsguideservice.com/mixedbagarchive.htmhttp://www.dbs.nus.edu.sg/research/fish/aquarium/catfish/catfish.htmhttp://www.dbs.nus.edu.sg/research/fish/aquarium/catfish/catfish.htmhttp://stewartsguideservice.com/mixedbagarchive.htm


10/22

Planktivores eat zooplankton, but fish tend to eat

more of some species and less of others.

Which species do they

select, which species do

they avoid and why?

Fish often select for

larger, more visible

prey items

photo by M. Duffy

There are 2 major

reasons why...


11/22

Pumpkinseed Lepomis gibbosus

1. Encounter frequency: Encounter of large prey is higherthan small prey

Reaction distancehowclose to the fish does a preyitem have to be for the fish

to see it and react to (eat)it?

www.state.ia.us/.../fwb/fish/ iafish/sunfish/pkse.gif

Confer and Blades 1975 (L&O)


12/22

Reaction distance translates to overall volume searched,which influences vulnerability of the prey

Volume searched = volume of sphere = 4/3 r3

Reaction distance = radiusof sphere

Visual field is roughly spherical with ~ 20posterior blind segment

Longer radius = higherencounter rate


13/22

2. Optimal foragingtake the prey that provides thegreatest energy return for cost of capture/handing.

With abundant prey, bigger is better

Werner and Hall (1974) Ecology

Fed fish choice of three sizes of Daphniamagna

0

20

40

60

80

Small (< 1.5 mm) Medium Large (>2.5 mm)

%i

ndiet

Expected from

encounter rates

Observed in Diet

Prey size

h l h ll h


14/22

Bluegills feeding on Daphnia

Get exception to this bigger is better rule with small fishbecause ofgape limitation Li et al. 1989 Ecology

Walton et al. 1992 Ecology

Selectivity

IndexNo choice

Avoidsparticularanimals

Selects forparticularanimals

0

-1

+1

Small fish dont eat large prey

Daphniasize (mm)

Fish > 76 mm

Fish = 11 mm


15/22

Two morphs of Ceriodaphnia

Big eye Small eye

It is not just size that matters, it is overall visibility

Artificially made small-eye morph more visible by feeding

them india ink. Predation rate increased

Zaret 1972

Fish always took the big-eye form.


16/22

Reproductive Behavior

Most common type of reproduction is ovipary (external

fertilization of eggs)

Parental care ranges from broadcast spawning to

mouthbrooding

Many species build nests

www.venturenorth.com/ tlca/bass.htm
http://www.venturenorth.com/tlca/bass.htmhttp://www.venturenorth.com/tlca/bass.htm


17/22

Reproductive Behavior in Bluegill

Large parental males mature at age 7

or 8

Nesting males court and spawn with multiplefemales

M.R. Gross and colleagues

Lake Opinicon, Ontario, Canada

Parental males compete for space to build a nest

The males care for all offspring in the nest


18/22

Reproductive Behavior in Bluegill

Some males mature at age 2 or 3sneakers

Other males mature at age 4 or 5satellites

M.R. Gross and colleagues

Sneakers do not make nests, but dart into the

nest while a female is releasing her eggs

Satellites look and act like females


19/22

Parental care

Males fan and defend the eggs

After the eggs hatch, males defend the fry

Males do not feed during this time and expend

about 10% of their body mass

Can determine paternity through genetic

analysis

Neff and Gross 2001


20/22

Neff and Gross 2001


21/22

Graeb et al. 2004 found that larval yellow

perch (< 12 mm) avoided eating large

Daphniaand primarily consumed copepod

nauplii, whereas larger perch (> 16 mm)avoided the nauplii and consumed the

Daphnia.

Explain this result


22/22

Concepts to know

What factors influence feeding of

planktivores?

What is the mating system in bluegill?

Instructor Lecture 5

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