EFFECTS OF TEMPERATURE AND SALINITY ON GROWTH PERFORMANCE IN CULTURED TRA CATFISH (Pangasianodon hypophthalmus) IN VIETNAM NGUYEN TRONG HONG PHUC Earth, Environmental and Biological Sciences Science and Engineering Faculty Queensland University of Technology Brisbane, Australia A thesis submitted in fulfilment of requirements for the degree of Doctor of Philosophy 2015 Keywords: Tra catfish, striped catfish, Pangasianodon hypophthalmus, climate change, aquaculture, temperature, salinity, growth performance, growth hormone, IGF-1, cortisol, osmotic pressure, plasma glucose concentration, hematological parameters, stress response, gene expression. STATEMENT OF ORIGINAL AUTHORSHIP The work contained in this thesis has not been submitted to meet requirements for an award at this or any other higher education institution. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made. QUT Verified Signature Nguyen Trong Hong Phuc July, 2015 WORKS PUBLISHED OR SUBMITTED FOR PUBLICATION BY THE AUTHOR INCORPORATED INTO THE THESIS Statement of Contribution to Jointly Authored Works in the Thesis 1. Nguyen, P. T. H., Do, H. T. T., Mather, P. B., & Hurwood, D. A. (2014). Experimental assessment of the effects of sublethal salinities on growth performance and stress in cultured tra catfish (Pangasianodon hypophthalmus). Fish Physiology and Biochemistry, Vol 40, 1839-1848. This manuscript is incorporated as chapter 2 of this thesis. The first author is responsible for the research, analysis and interpretation of data, and written work on this manuscript. The co-authors provide conceptual, logistical and editorial support. 2. Nguyen, T. H. P., Mather, P. B., Hurwood, D. A. (2015). Effects of temperatures on growth performance, hematological parameters and plasma IGF-1 level of tra catfish (Pangasianodon hypophthalmus). Journal of Thermal Biology, in review. This manuscript is incorporated as chapter 3 of this thesis. The first author is responsible for the research, analysis and interpretation of data, and written work on this manuscript. The co-authors provide conceptual, logistical and editorial support. 3. Nguyen, T. H. P., Duong, T. K. L., Mather, P. B., Hurwood, D. A. (2015). Effects of salinity, temperature and their interaction on growth performance, hematological and hormonal levels of tra catfish (Pangasianodon hypophthalmus). Aquaculture, in review. This manuscript is incorporated as chapter 4 of this thesis. The first author is responsible for the research, analysis and interpretation of data, and written work on this manuscript. The co-authors provide conceptual, logistical and editorial support. ACKNOWLEDGEMENTS First and foremost, my sincere thanks go to my supervisors Dr. David Hurwood and Prof. Peter Mather at the Science and Engineering Faculty, Queensland University of Technology (QUT), Australia for their supervision, advice, guidance and suggestion throughout the study programme and significant contribution to the planning and writing of the thesis and paper and also their friendly attitude. I am grateful to the Faculty of Aquaculture and Fisheries and Biotechnology Research and Development Institute of Can Tho University that offered facilities and technical assistances to conduct my studies. The research could not have been completed without the supports from my colleagues in the Faculty of Aquaculture and Fisheries and Biotechnology Research and Development Institute, their extensive assistances have been one of the most factors in the completion of this thesis. At the risk of offending the rest, I would like to name but a few: Prof. Nguyen Thanh Phuong, Assoc. Prof Do Thi Thanh Huong, Ms Nguyen Kim Ha, Mr. Do Tan Khang, Mr. Tran Van Be Nam, Ms Nguyen Loan Thao, Ms Tran Thi Kieu Linh, Ms Phan Vinh Thinh, Ms Nguyen Thanh Truc, Mr Nguyen Thanh Phong, Mr Nguyen Minh Tri, Ms Thi The Phuoc, Ms Tran Thanh Trang, Ms Huynh Thi Cam Tien for their supports for various aspects of this study. I would like to express my gratitude to the Australia Development Scholarship programme for providing a postgraduate scholarship for me to conduct research in Australia. The chance to do my PhD research in Australia has been one of the most valuable opportunities in my career and I therefore feel grateful to ADS and all the staff in the AusAID office at the QUT who provide me with necessary supports for my research and field works, supporting me in my efforts to complete this journey from the beginning till the end. I would like to give gratitude to my parents and my parents-in-law who always encourage me during a long period of study. On a personal note, I appreciate the sacrifices made by my wife, Duong Thi Kim Loan, to get me through this journey. Without her unconditional love and patient support during this time of period, there would be no thesis completed. And to my lovely daughter, Nguyen Phuc Minh Thu, with all of my heart. Abstract Tra catfish (Pangasianodon hypophthalmus) currently is the most important freshwater indigenous teleost cultured in the aquaculture sector in the Mekong River Delta (MRD) in Vietnam and it is now an icon of aquaculture development in Vietnam and globally. Over decades, the tra catfish industry has developed rapidly to a point where annual production now exceeds one million tonnes, employs nearly 200,000 rural poor, and resulted in export income of US$ 1.4 billion in 2010 (De Silva and Phuong, 2011). This industry however, has been identified as one that is likely to be impacted by predicted climate change scenarios because the MRD has been identified as among the top three most likely seriously affected regions around the world (IPCC, 2007). Predicted changes largely are related to water temperature increases caused by global warming and raised salinity caused by saline intrusion from sea level rise. The current situation highlights the need to assess potential effects of climate change on the tra catfish culture industry and to identify appropriate ways that will allow sustainable development of this important industry. The current study examined the responses of replicate cohorts of juvenile tra catfish to sublethal salinity and temperature change in three trials: (1) effects of raised sublethal salinities (freshwater, 2, 6, 10, 14 and 18‰); (2) effects of temperature levels (24, current ambient (27-28oC), 30, 32, 34, and 36oC); and (3) combined effects of temperature (25, 30, and 35oC) and salinity (freshwater, 6, and 12‰). Indicators for assessing effects of climate change on tra catfish performance included survival rate, growth performance, food conversion ratio, hormonal response (cortisol, growth hormone/IGF-1), osmoregulatory, plasma glucose and plasma ion concentrations, hematological parameters, and growth hormone gene expression patterns. Results of the first trial showed that tra catfish had high survival rates, better growth performance and better FCR values in a salinity range from freshwater to 10‰. Cortisol levels were elevated in the 14 and 18‰ treatments after 6 h and reached a peak after 24-h exposure, and this also led to increases in plasma glucose concentration. While fish in high salinity treatments did recover over a 14 days period, high salinity conditions had long- term negative effects on growth performance and FCR values. In trial 2, low temperature (24oC) significantly affected fish growth rate and FCR value while high sublethal i temperatures led to enhanced growth performance until 34oC where it peaked. Results of the 3rd trial showed that changes in temperature, salinity and their interaction had significant effects on individual growth rate and feed conversion efficiency of fish in the 35°C-6‰ treatment producing optimal conditions for growth while not producing significantly higher FCR values in comparison with a control treatment (freshwater - ambient temperature (25oC)). Tra catfish showed an effective capacity to acclimate successfully to changes in external environment factors (temperature and salinity), that included changing red blood cell count, hemoglobin concentration, metabolic rate, and energy mobilisation. Results of this study suggest that tra catfish can acclimate relatively easily to environmental conditions that have been predicted under current climate change models for the MRD. This provides strong indication that natural tra populations have the potential to adapt to higher salinity and temperature regimes relatively rapidly and therefore may persist successfully in the MRD for the long term. Furthermore, these data suggest that variation in genes underlying stress response to temperature and salinity that currently exist could facilitate development of culture strains that will perform well in the tra culture industry into the future. ii Notes on Thesis Preparation Chapters 2 to 4 of this thesis are presented as either published papers or as submitted manuscripts for publication. As such, there will be some necessary repetition of information in the General Introduction and General Discussion and Conclusions when compared against the Introductions and Discussions of individual data chapters. In Chapters 2 to 4, Figures and Tables in each chapter are re-initialized to maintain each chapter as an independent research paper. There is also some extra material that has been added to the data chapters that is relevant to the respective chapters but was not presented in the published papers/manuscripts. The reference list at the end of the thesis relates