COMPARATIVE REPRODUCTIVE BIOLOGY OF THE TASMANIAN FRESHWATER CRAYFISHES Astacopsis gouldi CLARK, Astacopsis franklinii, GRAY AND Parastacoides tasmanicus CLARK (DECAPODA: PARASTACIDAE) by Piemysl Hamr, B.SC. (Concordia), M.Sc. (Trent) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy University of Tasmania January, 1990. This thesis contains no material which has been accepted for the award of any other higher degree or graduate diploma in any tertiary institution, and to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference is made in the text of the thesis. f‘„,7 Piemysl Hamr, January 1990. "The northern Crayfish grows to nearly two feet in length, and may scale eight or nine pounds; it is dark green in colour, and studded on the claws and gill covers with blunt tubercles; the claws of the larger specimens are formidable weapons about the size of a man's hand. We obtained the largest specimens from Muddy Creek, a small rivulet that one could easily step across, and it seemed extraordinary to fish these huge monsters out of little pools in which one would expect to find nothing larger than a minnow." Geoffrey Smith, 1909 in "A Naturalist in Tasmania" Frontispiece: Astacopsis gouldi Clark ( immature crayfish, life size). TABLE OF CONTENTS Abstract Acknowledgements CHAPTER 1. GENERAL INTRODUCTION 1 CHAPTER 2. GENERAL METHODS 2.1 Study site selection and monitoring 6 2.2 Duration of study 7 2.3 Capture methods 7 2.4 Sample treatment 8 2.5 Marking system 9 2.6 Laboratory maintenance of animals 10 CHAPTER 3. SPECIES DESCRIPTIONS 3.1 Introduction and Methods 11 3.2 Results and Discussion 11 3.2.1 Species descriptions: Astacopsis 11 3.2.2 Key to the Genus Astacopsis 16 3.2.3 Analysis and discussion of taxonomic characters in Astacopsis 16 3.2.4 Species descriptions: Parastacoides 18 CHAPTER 4. DESCRIPTION OF STUDY SITES 4.1 Main study sites: Astacopsis 21 4.1.1 Inglis River 21 4.1.2 Hobart and Guy Fawkes Rivulets 22 4.2 Main study sites: Parastacoides 24 4.2.1 Harlequin Hill Plain 24 CHAPTER 5. REPRODUCTIVE MORPHOLOGY AND ANATOMY 5.1 Introduction 26 5.2 Methods 29 5.3 Results 30 5.3.1 Anatomy and development of gonads 30 A. Female gonad 30 B. Male gonad 30 5.3.2 Morphology and development of genitalia 32 A. Female gonopore 32 B. Male gonopore 34 C. Intersexuality 35 5.3.3 Secondary sexual characters / sexual dimorphism 36 A. Glair glands 36 B. Setation 37 C. Tail fan 38 D. Abdomen 39 E. Cephalothorax 40 F. Chelae 40 D. Body Weight 41 5.4 Discussion 42 CHAPTER 6. REPRODUCTIVE CYCLE 6.1 Introduction 50 6.2 Methods 51 6.3 Results 53 6.3.1 Maturity size 53 6.3.2 Seasonal breeding cycle of mature animals 57 6.3.3 Fecundity 71 6.4 Discussion 72 CHAPTER 7. REPRODUCTION / EMBRYONIC AND POST EMBRYONIC DEVELOPMENT 7.1 Introduction 84 7.2 Methods 85 7.3 Results 85 7.3.1 Copulation and spawning 85 7.3.2 Fertilization and egg attachment 89 7.3.3 Embryonic development 90 7.3.4 Postembryonic development 91 7.4 Discussion 95 CHAPTER 8. GROWTH / POPULATION DYNAMICS 8.1 Introduction 104 8.2 Methods 105 8.3 Results 106 A. Population dynamics 8.3.1 Monthly catchability 106 8.3.2 Sex ratio 107 8.3.3 Size frequencies 108 8.3.4 Population density 109 B. Moulting and growth 8.3.5 The moulting process 111 8.3.6 Seasonality of moulting 112 8.3.7 Moult increment and frequency 114 8.3.8 Growth rate and size at age estimates 116 8.4 Discussion 117 CHAPTER 9. GENERAL DISCUSSION AND SUMMARY 9.1 General discussion 123 9.2 Summary 131 REFERENCES 136 Appendix A. IMPACT OF RECREATIONAL FISHERY ON ASTACOPSIS GOULDI POPULATIONS. Appendix B. FOOD OF ASTACOPSIS . Appendix C. RELEVANT LITERATURE PUBLISHED BY AUTHOR ABSTRACT The reproductive biology and life history of the Tasmanian freshwater crayfishes in the endemic genera Astacopsis and Parastacoides were studied in the field and laboratory from April 1985 to May 1987. A. gouldi and A. franklinii are open water species associated with riverine and lacustrine habitats from highlands to coastal plains. The burrowing, semi- terrestrial P. tasmanicus occurs in wet heathlands, water courses and highland lakes in the wetter cooler, western half of the state. The three species were studied in representative, relatively undisturbed habitats. The habitats of all three species were typified by low water temperatures, high rainfall and fluctuating water levels. Reproductive morphology and anatomy of Astacopsis and Parastaco ides was described in detail. Male and female gonads differ from those of northern hemisphere crayfishes, resembling anatomically the gonads of the Palinuridae. The male gonopores show considerable complexity and variation among genera. Female genitalia undergo significant changes in morphology at the onset of sexual maturity. Sexual dimorphism is developed to a greater degree in Astacopsis than in Parastacoides. Secondary sexual characters are more numerous in females of both genera and perform important functions in spawning and incubation of eggs. Data on seasonal reproduction, growth, population structure and density were obtained from regular sampling and mark recapture programs. Size at maturity and reproductive condition were determined by changes in reproductive morphology and gonad condition. In both genera males reach sexual maturity at a smaller size than females. Females, upon reaching maturity, exhibit a biennial breeding and molting cycle which is a unique strategy, apparently a result of the cooler climate conditions in Tasmania. In Astacopsis, mating and spawning take „ place in autumn, eggs are carried over winter, hatch mid to late the following summer and young remain attached until late summer to early autumn. Parastacoides mates and spawns in autumn, eggs are carried over winter, hatch early the following summer and postlarvae remain attached until mid summer. The larval development and morphology of Astacopsis and Parastacoides was described. Marked differences between the two genera were found and the "primitive" larval development of Astacopsis differed significantly from that described for other freshwater crayfishes. - Growth rates, although faster in juveniles, are relatively slow in adults of both genera. In reproductive adults of both sexes, molting frequency is low (apparently biennial). This results in maturity being reached late and at a relatively large size as well as in overall longer life spans as compared to most other freshwater crayfishes. ACKNOWLEDGEMENTS I would like to thank Dr. A. M. M. Richardson for the advice, encouragement and amazing yabby digging ability he provided as the supervisor of this study. I would like to express my gratitude to the technical staff of the Zoology Department, in particular to Mr Ron Mawbey for suggesting sampling areas for Astacopsis franklinii and Mr Richard Holmes for fixing all my gear (especially the numerous tears in my waders). I would also like to thank Dr. Roy Swain for his assistance in the field and for introducing me to the Uni Soccer Club. I am greatly indebted to the friends who provided help in the field and endured hardships such as 3 day old fish bait, leeches, cask claret, sunstroke and frostbite (on the same South-West "summer" day), and painful pincer pinches. These "volunteers" are all too numerous to list but Ivor "Monty" Growns, Lee Hamr and Jean "action" Jackson deserve a special mention. I am also particularly grateful to Mr. Ray Wescombe from Penguin, North-West Tasmania, for showing me the Inglis and Dip River "lobster" populations and for his expert help in the field. I would like thank The Inland Fisheries Commission, Tasmania for their continued support during this study, issuing the appropriate collecting permits, providing me with a travel grant and access to their A. gouldi collection. I would also like to thank The Forestry Commission for providing me with access to the Choveaux plantation road and for letting me use the singleman's quarters during those cold winter months. Last but not least I would like to thank my wife Lee for her endless patience, understanding, physical and financial support and Benedikt for making me understand the full meaning of parental investment. CHAPTER 1 GENERAL INTRODUCTION Freshwater crayfishes (Superfarnilies Astacoidea and Parastacoidea) make up a significant component of the freshwater fauna of all continents except for Africa. Crayfishes found in the Northern Hemisphere belong to two families: 1. the Astacidae of Europe, western North America and western Asia; and 2. the Cambaridae of central and eastern North America, Middle America and eastern Asia. All crayfishes found in the Southern Hemisphere belong to one family: the Parastacidae. The family Parastacidae, Huxley 1879, which ranges from the tropics to the cool temperate subantarctic regions, contains the thirteen genera of crayfishes listed in Table 1.1. Australia's crayfish fauna can be seen to be particularly rich containing nine of the thirteen known genera mentioned above. Tasmania, although small in area when compared to the rest of the continent, has representatives of four of these genera (Engaeus, Geocharax, Parastacoides and Astacopsis) with Astacopsis and Parastacoides being endemic. The members of the genus Astacopsis, which include the world's largest freshwater crayfish (and therefore invertebrate) species, are associated with riverine and lacustrine habitats throughout Tasmania (Swain et al., 1982). Taxonomically and ecologically their closest relatives are the crayfishes of the genera Euastacus and Astacoides (Hobbs, 1987 & 1988; Riek, 1972; Patak & Baldwin, 1984). The genus was first erected by Huxley in 1878 but earlier accounts and descriptions of crayfish now placed in this genus are available (Gray, 1845; Gould, 1870). Perhaps the earliest representation of Astacopsis is a painting made in 1832 by the convict artist William Buellow Gould in his "Book of Fishes" (Fig.!.!).