<7 BEHAVIOURAL ECOLOGY OF THE LONGNOSE DACE, RHINICHTHYS CATARACTAE (PISCES, CYPRINIDAE): SIGNIFICANCE OF DACE SOCIAL ORGANIZATION by VICTOR GEORGE BARTNIK B.Sc. (Hons.), University of Manitoba, 1968 M.Sc, University of Manitoba, 1970 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY ,in the Department of ZOOLOGY We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1973 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of ZOOLOGY The University of British Columbia Vancouver 8, Canada Date ii ABSTRACT The social behaviour of a stream population of longnose dace, Rhinichthys cataractae dulcis, is described. Both males and females occupy the same riffle areas and defend territories (approx. 10 cm in diameter) during the breeding phase. In addition, male dace are evidently attracted to and interact agonistically with other males resulting in the formation of clusters of male territories. During the night, females leave their territories to court and spawn with terri• torial males. After spawning, males show strong nest site attachment and are inhibited from eating eggs. Parental males remain directly over the nest site and frequently probe the substrate with their snouts. They defend the area against all fish with the exception of receptive females with which they may spawn. Comparison with a stream population of the sub-species, R. cataractae cataractae, reveals differences in phenotypic appearance, diurnal rhythm of breeding activity, and female territoriality. Unlike R.c.. dulcis, R.c^. cataractae are reproductively active during daylight hours and males display bright nuptial coloration. Breeding coloration in males of R.£. dulcis is faint or absent. Unlike R.c. dulcis, males and females of R.c. cataractae are segregated into different habitats and females remain non-territorial. Experimental analyses of the physical and biotic factors involved in the causation of territorial behaviour were conducted in a laboratory stream tank. The major physical factor involved in the selection of territories by male dace is the presence of coarse gravel suitable for iii spawning. Female dace select and defend only enclosed areas which provide both overhead cover and shelter from current. Females prefer shelters which contain food and thus the presence of food may be a proximate factor involved in the selection of territories by female dace. Laboratory tests indicate that female territorial behaviour is elicited by interaction with breeding males. Outside the breeding phase, when territoriality is relaxed, male and female dace differ little in the areas they choose to occupy. The experimental evidence suggests that the functions of male territory are: i) provision of space in which males can court and spawn with females with minimal interference from other males, and ii) protection of eggs from intraspecific predation. For females, territoriality apparently functions to reduce conflicts with males (i.e., reduce court• ship harassment and attacks from males). Changes in the behaviour of males occur after spawning and coincide with periods of greatest egg vulnerability. These post spawning behavioural activities of males protect freshly deposited eggs while making them less accessible to predators. The evidence also suggests that a major function of territory in both sexes is the provision of shelter from current. Dace not defending a shelter may be forced to make frequent movements in the strong current of the riffle habitat. Dace swimming against strong currents for even short periods (i.e., 5 min) become fatigued and lose their ability for co• ordinated locomotion. Such stressed individuals may be vulnerable to predation. The data also suggest that dace territorial behaviour may act as a dispersing mechanism, thereby limiting the density of breeding fish in a localized area. iv Territorial males of clustered groupings remain behaviourally synchronized. They display strong site attachment and interfere little with the reproductive activities of neighbouring males. Consequently, these social groupings function to further reduce interference from conspecifics. Assemblages of more widely spaced territorial males, created in the laboratory, experienced greater intraspecific interference and egg predation than did males of clustered territorial groupings. Thus it seems most probable that intraspecific interference and egg predation have provided a major selection pressure favouring both male territori• ality and territory clustering in longnose dace. :.v TABLE OF CONTENTS Page LIST OF TABLES xi LIST OF FIGURES . .... xiii ACKNOWLEDGEMENTS xvli INTRODUCTION 1 MATERIALS AND METHODS . 4 A. Study Area 4 B. Holding Conditions ^ C. Description of Stream Tank 6 D. Experimental Channels 6 E. Experimental Conditions 8 F. Experimental Fish 9 SECTION I: THE SOCIAL BEHAVIOUR OF LONGNOSE DACE • H A. Description of the Behaviour of R.c_. dulcis H a. Reproductive Behaviour H b. Agonistic Behaviour Patterns Recorded During 1* Observations c. Courtship Behaviour Patterns Recorded During Observations ; ^ d. Egg Eating Inhibition ^ i. Outline of Experiment ^ ii. Procedure 17 iii. Experimental/Fish 18 iv. Results and Discussion 18 e. Comparison with R. £. cataractae 20 Page B. Summary and Discussion . 27 SECTION II: FACTORS INVOLVED IN THE CAUSATION OF TERRITORIAL BEHAVIOUR AND THE SELECTION OF A TERRITORY 31 A. Breeding Phase 32 a. Experimental Analysis of the Factors Involved in the Selection of Territories by Male and Female Dace 32 i. Outline of Experiment ;. 32 ii; Procedure. 35 iii. Experimental Fish...... 37 iv. Results and Discussion 37 b. Social Factors Affecting Territorial Behaviour in Female R. c_._ dulcis 45 i. Outline of Experiment 45 ii. Procedure........ 45 iii. Experimental Fish . 46 iv. Results and Discussion 46 c. Social Factors Affecting Territorial Behaviour in Female R.c:. cataractae .................. 49 i. Outline of Experiment.... 49 ii. Procedure 49 iii. Experimental Fish 51 iv. Results and Discussion 51 d. Social Factors Affecting Territorial Behaviour in Male R.c. dulcis 56 via. Page e. Clustering of Male Territories... 58 i. Outline of Experiment 58 ii. Procedure . ... ,. 60 iii. Experimental Fish 62 iv. Results and Discussion .. ... 62 f. Behaviour of Clustered Territorial Male Dace... 66 i. Outline of Experiment 66 ii. Procedure 67 iii. Experimental Fish • ^ iv. Results and Discussion ... 69 g. The Role of Food in the Distribution of Dace Territories 73 i. Outline of Experiment... 73 ii. Procedure 73 iii. Experimental Fish 75 iv. Results and Discussion , 75 B. Non-Breeding Phase .... 80 a. Site Preferences of Male and Female Dace in Late Summer and Winter.. ... 80 i. ' Outline of Experiment 80 ii. Procedure 82 iii. Experimental Fish 82 iv. Results and Discussion .... 82 viii Page b. Seasonal Variation in the Spacing Patterns of Dace 88 i. Outline of Experiment........ 88 ii. Procedure 88 89 iii. Experimental Fish iv. Results and Discussion 89 c. Role of Food in the Distribution of Dace in LateSSummer 93 i. Outline of Experiment 93 ii. Procedure .... 93 iii. Experimental Fish 93 iv. Results and Discussion • 94 C. Spacing Patterns of Dace Fry/ 94 i. Outline of Experiment 94 ii. Procedure 97 iii. Results and Discussion........ 97 D. Discussion of the Causation of Territorial Behaviour 99 SECTION III: THE FUNCTIONAL SIGNIFICANCE OF THE SOCIAL ORGANIZATION OF DACE.. 104 A. Introduction 104 B. Inferences from Observations and Experiments in Section II as to the Function of Various Aspects of Territorial Behaviour 105 ix Page C. Experimental Tests of Hypotheses Regarding Function.... 106 a. Significance of Territory Clusters 106 i. Outline of Experiment.. .. 106 ii. Procedure.....:. ••• 107 iii. Experimental Fish •••• 109 iv. Results and Discussion 110 b. Significance of Post Spawning Changes in Male Behaviour 118 c. Significance of Male Territory as Determined by Vulnerability of Dace Eggs to Intraspecific Predation .. 122 i. Outline of Experiment ...... 122 ii. Procedure............ 122 iii. Experimental Fish 124 iv. Results and Discussion 125 d. Other Predators ... 129 i. Trout... ... 129 ii. Sculpins • • 130 iii. Egg Predation... 131 e. Significance of Female Territory as Determined by Changes in Blood Lactate in Dace after Exercise 134 i. Outline of Experiment 135 ii. Procedure . 136 iii. Experimental Fish 138 iv. Results and Discussion 139 X Page f. Territorial Behaviour as a Dispersing Mechanism 141 i. Outline of Experiment 141 ii. Procedure..... •• 142 iii. Experimental Fish 144 iv. Results and Discussion... 144 D. Discussion of the Significance of Social Organization in Dace • • • • 148 LITERATURE CITED • 154 XX LIST OF TABLES Table Page I. Number of eggs eaten by different types of dace presented with recently fertilized eggs 19 II. Agonistic behaviour patterns commonly performed by R.-c. cataractae and R._c. dulcis during the breeding phase.. 24 III. Environmental features incorporated into experimental structures.... 34 IV. Mean number of agonistic acts won per 30