Antipredator behaviour of Baltic planktivores

0,41

MB

58

stron

3781

ID

Finnish Institute of Marine Research

2006

rok

CONTENTS

1. INTRODUCTION .. 7

1.1 Predation . 7

1.2 Predator detection 10

1.3 Antipredator behaviour . 11

1.3.1 Decreased activity .. 12

1.3.2 Swarming 13

1.3.3 Hiding . 13

1.3.4 Migration 14

1.3.5 Flight 15

2. STUDY AREA .. 15

2.1 Baltic Sea 15

2.2 Ekenäs Archipelago 16

3. STUDY OBJECTS . 16

3.1 Littoral mysids . 16

3.2 Pelagic mysids . 18

3.3 Predatory cladoceran Cercopagis pengoi 19

3.4 Three-spined stickleback Gasterosteus aculeatus .. 21

3.5 Predators . 21

3.6 Aquatic macrophytes . 22

4. OBJECTIVES OF THE STUDY .. 23

5. MATERIALS AND METHODS .. 24

5.1 Laboratory experiments 24

5.1.1 Sampling . 24

5.1.1.1 Littoral planktivores 24

5.1.1.2 Pelagic planktivores . 24

5.1.1.3 Predators 24

5.1.1.4 Aquatic macrophytes .. 24

5.1.1.5 Zooplankton and brine shrimp 25

5.1.2 Feeding experiments . 25

5.1.3 Video fi lming 25

5.1.4 Swarming experiments 26

5.1.5 Mortality experiments .. 26

5.2 Field studies .. 26

5.2.1 Mortality experiments .. 26

5.2.2 Distribution study .. 27

5.3 Statistical analyses and equations 28

6. RESULTS AND DISCUSSION . 29

6.1 Predator detection 29

6.2 Decreased activity 30

6.3 Prey selection 31

6.4 Swarming 33

6.5 Hiding .. 34

6.6 Effects of aquatic vegetation .. 36

6.6.1 Mortality . 36

6.6.2 Distribution 37

7. CONCLUSIONS .. 39

8. ACKNOWLEDGEMENTS . 40

9. REFERENCES . 41