The feeding ecology and physiology of vagrant Chaetodon species on temperate

New South Wales reefs

Marcus A Gregson

Dept Environmental Sciences

Institute for Water and Environmental Resource Management

University of Technology, Sydney

Supervisors:

Professor David J Booth (UTS)

Dr Morgan S Pratchett (James Cook University)

Introduction

•East Australian Current

•Vagrant Species

CSIRO Images

Heath Folpp, NSW Fisheries

Feeding Interactions

Morphological Factors Environmental Factors

•Body size and energy needs

•Digestive/ buccal system

•Presence of suitable prey

•Environmental conditions

Prey Intake

Growth and Condition

Adapted from Drickamer et al 2002

•Competitors

•Predators

Social Factors

Current Study

Latitudinal differences in feeding ecology of juvenile Chaetodons

H0i: Chaetodon diet does not differ between tropical and temperate regions

H0j: Difference in diet does not affect Chaetodon growth or condition

Study Species

www.daveharasti.comRandall JE, www.fishbase.org

Chaetodon auriga Chaetodon flavirostris

Family: Chaetodontidae

Methods

Locations

•Sydney (3 sites)

•One Tree Island (3 sites)

Melbourne

Canberra

SYDNEYNewcastle

Brisbane

ONE TREE ISLANDRockhampton

Townsville

Cairns

Hobart

MethodsH0i: Chaetodon diet does not differ between tropical

and temperate regions• Food Intake: Bite Rate• Potential Prey: Grazing Surface• Actual Diet: Gut Content Analyses

H0j: Difference in diet does not affect Chaetodon growth or condition• Body Condition: Fulton’s Condition k

H0i: Chaetodon diet does not differ between tropical and temperate regions

Bite Rate

0

2

4

6

8

10

12

14

16

18

20

22

Sydney One Tree Island

Mea

n B

ite R

ate

(5 m

in)

C. auriga

C. flavirostrisn=42 n=16n=27 n=10

Factor p

Location 0.293

Species 0.829

Location*Species 0.547

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Pro

po

rtio

n o

f T

ota

l B

ites

0

0.1

0.2

0.3

0.4

0.5

0.6

Bare EncrustingCoralline

Sediment MacroAlgae

Amphiroaanceps

Othercoralline

Turf algae

Pro

port

ion

of T

otal

Bite

s

C. flavirostris

Sydney

C. auriga

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Pro

po

rtio

n o

f T

ota

l B

ites

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Scleractinia CoralRubble

Sediment Rhodolith MacroAlgae

Pro

po

rtio

n o

f T

ota

l B

ites

One Tree Island

C. auriga

C. flavirostris 0

0.1

0.2

0.3

0.4

0.5

0.6

Bare EncrustingCoralline

Sediment MacroAlgae

Amphiroaanceps

Othercoralline

Turf algae

Pro

po

rtio

n o

f T

ota

l Bit

es

Prey Items Found in the Field

1 mm 1 mm

1 mm1 mm 1 mm

Gut Content Analyses: Chaetodon aurigaMean Volume at Sydney and One Tree Island

Sydney

Coral

Unidentif ied

Crustacea

Polychaete

Polychaete Setae

One Tree Island

Sydney Ranking Index

(occurrence X volume) (Harmelin-Vivien & Bouchon-Navaro 1983)

Coral 0

Unidentified 316

Crustacea 160

Polychaete 9221

Polychaete Setae 13

1 mm

n=9

n=11

H0i: Chaetodon diet does not differ between tropical and temperate regions

Gut Fullness: Chaetodon auriga

t = 3.04, df=11, p= 0.011

0

2

4

6

8

10

12

14

16

One Tree Island Sydney

Mea

n G

ut

Fu

lln

ess

Ind

ex

(100

0*[G

CW

/(W

T-G

CW

)])

n=9n=11

t= -3.04, df= 12, p= 0.005

H0j: Difference in diet does not affect Chaetodon growth or condition

Fulton’s Condition k: C. auriga• k= 105*[w/l3]

t=1.77, df=13, p=0.359

2.5

2.55

2.6

2.65

2.7

2.75

2.8

2.85

2.9

2.95

3

Sydney One Tree Island

Me

an

Fu

lto

n's

Co

nd

itio

n k

n=9 n=13

t= 0.369, df=13, p=0.36

Summary and Future Research•Food Intake: Bite rate does not differ between Sydney

and One Tree Island-Gut fullness of Chaetodon auriga in Sydney suggests there is ample food available

•Potential Prey: Chaetodon species at both Sydney and One Tree Island exploit habitats of high

macroinvertebrate diversity and abundance•Diet: Sydney Chaetodon auriga appear to eat a much

higher volume of polychaetes than those at One Tree Island

•Body Condition: Despite this variation in diet, no difference in body condition

Acknowledgements• Research was supported by an ARC Discovery Grant

(DP0560005- D Booth) “The mechanisms of settlement success in coral reef fishes”

• Matt and Ali at One Tree Island Research Station

• Pat Hutchings at Australian Museum for polychaete ID assistance