Preface VII

I Communities 1

River donation and classification schemes 1
Functional classification of stream animals 2
The River Continuum Concept 5
General features of Hong Kong running waters 6
Longitudinal donation along the Lam Tsuen River 7
The river valley 7
Characterisation of the river fauna 8
Spatial arid temporal variations in benthic communities 12
Functional organisator of benthic communities 18

The stream and its valley 21
Tai Po Kau Forest Stream 21
General characteristics: the abiotic environment 21
Microdistribution of benthic animals 24
General characteristics: the biotic envirronment 26
The tropic basis of production 27
Riparian vegetation and stream communities 28
Comity composition 28
Functional organisation 32

Land-water interactive systems 34

II Populations 37

Life cycles and population dynamics in a seasonal tropical environment 37
The Hong Kong climate 37
Mollusca 40
Crustacea 44
Insecta 46
Fishes 50
Herpetofauna 52
Recapitulation: seasonality of lotic populations 53

Drift of the stream fauna 54
Diel periodicity 54
Seasonal fluctuations 57
Population implications of drift 59

Interspecific competition and niche dimensions 61
Odonata 61
Fishes 63
Is competition important in Hong Kong streams? 65
Biotic versus abiotic influences on lotic populations 66

III Individuals 68

Adaptation and optimal animals 68
Feeding 69
Foraging behaviour: predators 70
Foraging behaviour: primary consumers 76
Feeding apparatus and diet: mayfly larvae 79
Feeding apparatus and diet: net-spinning caddisflies 87
Morphological adaptations for life in running waters 93
Optimal animals revisited 98

IV The human factor 100

Stream vulnerability 100
Pollution 100
River regulation 101
Exotic invaders: overview 103
Attributes of invasive species 105
Ecological effects of exotic species 107
Where are exotic species most successful? 108
Is there reason for concern over exotic species 109
The future 109

V Synthesis 111

Acknowledgements 115
References 117
Index 141