Food and feeding ecology of the common dolphin, Delphinus

0,99

MB

delphis, in the Bay of Biscay: intraspecific dietary variation and

85

stron

food transfer modelling

4872

ID

University of Aberdeen

2004

rok

TABLE OF CONTENTS

CONTENTS Pages

Chapter I – INTRODUCTION 1

Chapter II MATERIALS AND METHODS 6

II.1. Collection of samples 6

II.2. Sample analysis 8

II.3. Data analysis 10

II.3.1. Estimation of individual prey body size and mass 10

II.3.2. Indices of prey importance 10

II.3.3. Sample size consideration and error assessment 11

II.3.4. Consideration of different digestion rates 11

II.3.5. Exploratory and statistical analyses 13

Chapter III THE DIET OF THE COMMON DOLPHIN AND ITS

VARIATIONS 15

III.1. Structure of the sample set 15

III.2. Diet composition 16

III.2.1. Prey composition 16

III.2.2. Prey sizes 19

III.2.3. Effect of sample size 22

III.2.4. Consideration of fresh versus complete stomach content composition 25

III.3. Variability in the diet of common dolphins 27

III.3.1. Interindividual variability 27

III.3.2. Interannual variations 30

III.3.3. Seasonal variations 33

III.3.4. Variations related to reproductive status 35

Chapter IV FEEDING ECOLOGY OF COMMON DOLPHIN IN THE

NERITIC BAY OF BISCAY 39

IV.1. Overall diet of common dolphins and comparisons with other studies 39

IV.2. Feeding behaviour of the common dolphins 41

IV.3. Comparison with the diet of other cetaceans occurring in the area 42

IV.4. Overlap with fisheries 43

IV.5. Temporal variations in relation to prey availability 45

IV.5.1. Longterm variations 45

IV.5.2. Shortterm variations (years and seasons) 46

IV.5.2.1. Betweenyear variations

IV.5.2.2. Seasonal variations

IV.6. Demographic variations 48

IV.7. Consideration of limitations due to the methods 49

IV.7.1. Characteristics of stranded animals 49

IV.7.2. Degree of accuracy of dietary composition 50

IV.7.3. Consideration of prey speciesspecific digestion rates 50

Chapter V – EFFECTS OF DIETARY VARIATIONS ON FOOD TRANSFER

MODELLING 52

V.1. Dietary variations on models in the literature 52

V.2. Application of the observed variations in dietary composition 54

V.2.1. Methods 55

V.2.2. Results and Discussion 56

V.2.2.1.Individual daily consumption of common dolphin

V.2.2.2.Intake of contaminants to common dolphin

CONCLUSION 62

REFERENCES

APPENDICES

LIST