SPAWNING AND LARVAL REARING OF THE MONKEY RIVER PRAWN Macrobrachium lar (FABRICIUS, 1798) (CRUSTACEA: DECAPODA: CARIDEA: PALAEMONIDAE) IN THE FIJI ISLANDS by Monal M. Lal A thesis submitted in fulfilment of the requirements for the Degree of Master of Science in Marine Science Copyright © 2012 by Monal M. Lal School of Marine Studies Faculty of Science, Technology and Environment University of the South Pacific Digitally signed by Monal Lal April, 2012 Date: 2011.11.01 20:11:29 +13'00' COLLABORATING INSTITUTIONS ____________________________________________________________________ Frontispiece: male M. lar specimen DECLARATION OF ORIGINALITY ____________________________________________________________________ Statement by Author I, Monal M. Lal, declare that this thesis is my own work and that, to the best of my knowledge, it contains no material previously published, or substantially overlapping with material submitted for the award of any other Degree at any institution, except where due acknowledgement is made in the text. ________________________ ______________02/11/2011 Monal M. Lal Date S11020445 Statement by Supervisors The research in this thesis was performed under my supervision and to my knowledge is the sole work of Mr. Monal M. Lal. _________________________ ______________02/11/2011 Mr. Johnson Seeto Date Principal Supervisor _________________________ ______________02/11/2011 Dr. Timothy Pickering Date External Supervisor DEDICATION ____________________________________________________________________ This thesis is dedicated to the Almighty for His guidance and providence and to my mother for her love and support. i ACKNOWLEDGEMENTS ____________________________________________________________________ I would like to acknowledge the Australian Centre for International Agricultural Research (ACIAR), who through their USP-ACIAR Scholarship scheme made it possible for me to study for my Master of Science Degree. My sincere thanks and gratitude go to Ms. Cathy Hair for her advice and assistance with getting the project underway. To my principal and external supervisors Mr. Johnson Seeto and Dr. Timothy Pickering, I thank you very much for your invaluable advice, comments, criticisms, encouragement and feedback throughout the duration of the study. A big vinaka vakalevu to Tim Pickering for securing the Pacific Aquaculture Grant which funded the research and your help with the experimental designs among many other aspects of the study, and the reminders to “focus on your objectives!”. Vinaka vakalevu also to Johnson Seeto, who later told me he knew all along that we would produce PL, when I really did not think it possible. I am immensely grateful to Mr. Tomohiro Imamura, for teaching me his Rua-Cell System of greenwater culture, without which it would have been extremely difficult to attempt to rear the larvae of M. lar; and for his technical assistance and guidance during the trial phase of the project. I am also grateful to Mr. Maika Ciqo of the Naduruloulou Research Station who collected the majority of the prawn broodstock used for hatching larvae during the study, Dr. Simon Hodge for assistance with the statistical analyses carried out for the salinity and temperature experiments and Dr. William Camargo for use of bench and floor space in the Seawater Laboratory at USP. I acknowledge the assistance of Mrs. Liti Muavesi, who provided me with moci at the Nausori Market when required and Mrs. Cherie Soro of Celtrock Holdings for sourcing whole squid which were required as larval feed ingredients. My gratitude ii also extends to the Frey family; Andreas, Peter and Dawn for the many discussions over dinner and encouragement and support. I am particularly grateful to Ms. Sarah Myhre and Ms. Kristen Anderson of the PRAISE information service at the University of Hawaii, who were able to source obscure pieces of literature for me that I otherwise would not have had access to. I am also grateful to Mr. Deepak Kissun who shared with me his literature on M. lar and his experiences with culturing the larvae. I would also like to extend my gratitude to staff of the School of Marine Studies at USP; Mr. Jone Lima, Mr. Shiv Sharma and Mrs. Nanise Bulai for the provision of and assistance with purchasing equipment required for the project. The assistance of staff of the Institute of Marine Resources; Mrs. Shirleen Bala, Mrs. Cherie Morris, Mr. Avinash Singh and Miss. Prerna Chand is also acknowledged. Finally, to my friends for all your support and encouragement, thank you all; Mr. Viliame Waqalevu, Mr. Kelly Brown, Adi Siteri Tikoca, Miss. Mere Naisilisili for help with image processing of the composite larval photographs, Miss. Laura Williams and Ratu Rusiate and Mrs. Ana Vadiga for the time we shared in the laboratory. iii ABSTRACT ____________________________________________________________________ The Monkey River Prawn Macrobrachium lar (Fabricius, 1798) is a large palaemonid prawn indigenous to a number of Pacific Island Countries and Territories (PICTs). Because of its size, relatively fast growth rates and a number of other favourable characteristics, it appears to have good potential for aquaculture except for one major constraint; namely the availability of seed stock for grow-out which is severely limited by the inability to rear the larvae from hatch until metamorphosis into post-larvae (PL). A greenwater-type technique developed for M. lar larviculture is described here, and was successful in producing PL, representing possibly the first time that this has been reported for this species. The larvae of M. lar developed through 13 zoeal stages before metamorphosing to PL1, moulting within 22 – 31 or more instars at salinities of 30 ± 1.5 ‰ and temperatures of 28 ± 0.8 l of five post-larvae were produced, after 77, 78, 85, 101 and 110 days of culture respectively. Overall percentage survival to PL1 was very low, at 0.08 %. Larvae were observed to undergo mark-time moulting during development, especially during the later zoeal stages as metamorphosis approached, which lengthened overall culture duration. This is attributed to inappropriate culture conditions, especially in terms of larval nutrition and possibly salinity. A point of difference noted between the feed preferences of M. lar and other Macrobrachium spp. larvae was that the former showed a strong tendency to consume biofloc particles in preference to Artemia nauplii, when both were present in sufficient quantities. The embryonic development of M. lar appears very similar to that which has been described for other species of Macrobrachium. Ovigerous females of M. lar maintained in the laboratory displayed asynchronous and prolonged hatching, which resulted in relatively low larval yields at the commencement of rearing trials. iv Embryonic development was found to take approximately 29 days from the time of oviposition until hatch at 28 ± 0.5 Through a series of salinity and temperature tolerance experiments, it has been established that the larvae of M. lar are able to hatch in either freshwater or brackish-water of approximately 10 ‰, but require gradually increasing salinities post-hatch reaching 30 – 35 ‰, which probably needs to be maintained until metamorphosis into PL. Larval stages I – II require a range of 10 – 15 ‰, III – IV require 15 – 25 ‰ and V – VI require 25 – 30 ‰. Stages VII to XIII require 30 – 35 ‰ following which salinity may be reduced after PL1 is reached. Larval survival and growth were found to be significantly different (Repeated Measures ANOVA and One-Way ANOVA; p <0.05) between larvae maintained within and outside these salinities. Larvae kept in freshwater (0 ‰) die within 4 days unless transferred to brackish-water. A salinity acclimation protocol has also been developed that will be useful in developing a mass culture technique for hatchery production of PL. Results of the temperature tolerance investigations revealed that a temperature range of 30 ± 0.5 Measures ANOVA and One-Way ANOVA; p <0.05). Given these results, pilot commercial-scale larviculture of M. lar does not appear to be feasible over the short to medium term, and the capture and culture of wild juveniles will have to be relied upon at present for developing pond-based culture of this species. Over the longer term, given that it took time for M. rosenbergii larviculture to become sufficiently practical for successful aquaculture, there is room for similar improvement for M. lar which warrants further research. Keywords: Larviculture, Macrobrachium lar, larvae, PL, zoea, greenwater, Pacific Islands, salinity, temperature, survival, growth. v ABBREVIATIONS AND ACRONYMS ____________________________________________________________________ ABW Average body weight ACIAR Australian Centre for International Agricultural Research BFT Biofloc Technology CL Carapace length -1 DO2 Dissolved oxygen (usually specified in mgL ) EDTA Ethylene diamine tetraacetic acid disodium salt (C10H14N2Na2O8.2H20) Fam. Family (taxonomic hierarchy) Fij. Fijian (name of the subject in the Fijian language) FRP Fibre-reinforced Plastic GSL Great Salt Lake, Utah, United States of America ind. Individual(s) JICA Japan International Cooperation Agency min. Minute NACA Network of Aquaculture Centers in Asia-Pacific PICTs Pacific Island Countries and Territories PL Post-larva(e); PL1 denotes the first post-larval instar, PL2 denotes the second instar and so forth PVC Polyvinyl chloride SMS School of Marine Studies TDR Total daily ration TL Total length Treflan Antifungal agent used