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The feeding ecology and physiology of vagrant Chaetodon species on temperate New South Wales reefs Marcus A Gregson Dept Environmental Sciences Institute.

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Presentation on theme: "The feeding ecology and physiology of vagrant Chaetodon species on temperate New South Wales reefs Marcus A Gregson Dept Environmental Sciences Institute."— Presentation transcript:

1 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)

2 Introduction East Australian Current Vagrant Species CSIRO Images Heath Folpp, NSW Fisheries

3 Feeding Interactions Morphological FactorsEnvironmental 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

4 Current Study Latitudinal differences in feeding ecology of juvenile Chaetodons H 0i : Chaetodon diet does not differ between tropical and temperate regions H 0j : Difference in diet does not affect Chaetodon growth or condition

5 Study Species www.daveharasti.com Randall JE, www.fishbase.org Chaetodon aurigaChaetodon flavirostris Family: Chaetodontidae

6 Methods Locations Sydney (3 sites) One Tree Island (3 sites) Melbourne Canberra SYDNEY Newcastle Brisbane ONE TREE ISLAND Rockhampton Townsville Cairns Hobart

7 Methods H 0i : Chaetodon diet does not differ between tropical and temperate regions Food Intake: Bite Rate Potential Prey: Grazing Surface Actual Diet: Gut Content Analyses H 0j : Difference in diet does not affect Chaetodon growth or condition Body Condition: Fulton’s Condition k

8 H 0i : Chaetodon diet does not differ between tropical and temperate regions Bite Rate n=42 n=16 n=27 n=10 Factorp Location0.293 Species0.829 Location*Species0.547

9 C. flavirostris Sydney C. auriga

10 One Tree Island C. auriga C. flavirostris

11 Prey Items Found in the Field 1 mm

12 Gut Content Analyses: Chaetodon auriga Mean Volume at Sydney and One Tree Island Sydney Ranking Index (occurrence X volume) (Harmelin-Vivien & Bouchon-Navaro 1983) Coral0 Unidentified316 Crustacea160 Polychaete9221 Polychaete Setae13 1 mm n=9 n=11

13 H 0i : Chaetodon diet does not differ between tropical and temperate regions Gut Fullness: Chaetodon auriga t = 3.04, df=11, p= 0.011 n=9 n=11 t= -3.04, df= 12, p= 0.005

14 H 0j : Difference in diet does not affect Chaetodon growth or condition Fulton’s Condition k: C. auriga k= 10 5 *[w/l 3 ] t=1.77, df=13, p=0.359 n=9 n=13 t= 0.369, df=13, p=0.36

15 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

16 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

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