Does aquaculture diet composition influence the nutrition retention and condition of wild-caught Acanthopagrus butcheri broodstock? Submitted by Jesse Isaiah Newton This thesis is presented for the degree of the Bachelor of Science Honours College of Science, Health, Engineering and Education, Murdoch University, 2020 Cover Image. A wild Acanthopagrus butcheri captured from the Murray River region of the Peel-Harvey Estuary and used for the feed trial conducted in this study. Photograph by Jesse Newton. Abstract Aquaculture is an essential industry for global food security, with production surpassing that obtained from wild capture fisheries. Future development of this profit- driven industry to meet the needs of a rapid growing population is dependent on the improved efficiency and sustainability of feeding methods. The health and nutrition of broodstock is crucial as it directly influences larval development and survival. Wet diets of whole fish and cephalopods are often fed to broodstock, however, they are abundant in long-chain highly unsaturated fatty acids and high rancidity making them prone to oxidation while in storage. Oxidation makes feed products rancid and degrades reproductive organs in fish, namely the livers. This leads to smaller spawns and reduction in larval survival. Aquaculture production is often limited by poor larval performance as a direct influence of inadequate knowledge of broodstock nutritional requirements. Due to the variance in nutritional requirements at a species level, investigative research is required. Acanthopagrus butcheri, an important recreational fishing species in Australia, fits the criteria for diversification of small-scale aquaculture production outlined by the Food and Agricultural Organisation of the United Nations. This study aims to investigate the impacts of aquaculture diets on the physiological health of wild caught A. butcheri broodstock, by measuring the transfer of dietary nutrients from the following commercial aquaculture diets, frozen squid and pilchards, Breed-M broodstock conditioning diets and C2, a powdered larval diet combined with gelatine into pellets. Breed-M and C2 provided superior fatty acid profiles and antioxidant defence, while pilchards had high rancidity values which led to oxidation of liver tissue. Livers from wild caught fish reflected the lowest oxidation values, despite also containing minimal levels of antioxidants. Breed-M and C2 provide antioxidants and fatty acids that are excessive of A. butcheri requirements, however wet fish diets of pilchards result in rapid degradation of valuable broodstock, negatively impacting growth and the physiological condition of reproductive organs. This study provides insight into the dietary requirements of finfish broodstock and shows the implications of insufficient broodstock nutrition in aquaculture production. Acknowledgements I would like to thank my supervisory team of Drs. Gavin Partridge, Ben Roennfeldt, Alan Cottingham and James Tweedley for your advice, help and support throughout. The time dedicated to assisting this project from its beginning to the submission of this thesis has been invaluable to me and I am extremely appreciative of what has been a steep learning experience. Having the input from each of your areas of expertise has enabled me to learn from multiple perspectives and for that I am grateful. Many thanks go to Dr. Ben Roennfeldt, who almost single handedly designed and built the aquaculture facility! Your Bream expertise was invaluable, especially when you caught double my weekly catch in one day to get us started. This project could not have worked without the assistance from Dr. Gavin Partridge and the team at Australian Centre for Applied Aquaculture Research (ACAAR) who helped leading up to and throughout the trial, producing the C2 feed, assisting with sample analysis and allowing me to utilise their facilities. Thanks go to the Peel-Harvey Catchment Council and John Tonkin College for their collaboration and support of this project and to Tackleworld Miami, for assisting in the capture of our broodstock and engaging the local community so they could take part in fishing for our broodstock. Thank you to the Department of Primary Industries and Regional Development Diagnostic Laboratory Services, for allowing me to work in the lab so I gain experience and a better understanding of the analyses and also PathWest and Vetpath laboratories for working to process our samples as fast as they did during such a restricting and uncertain time. A special thanks to Charlie, you kept me connected to the outside world when you helped with late night tank cleaning and water changes and made me feel somewhat normal, when you were still processing mussels in the lab next to me beyond midnight. To all of the other volunteers that helped me along the way, I would not have been able to complete this project without your assistance. The journey of transforming a dusty storage shed to a successful aquaculture facility, the road trips to catch broodstock (many unsuccessful) and the very long final day, helping to complete the trial. These all took many hands and minds and I appreciate the time you lended me. To Hayley, your unwavering support, encouraging words and constant belief in me through the past 18 months has been invaluable. Theres noone else I would have rathered to dissect fish with until 3am and I wouldn’t have had clean clothes or a proper meal for the final six months if it wasn’t for you. Table of Contents 1 Introduction......................................................................................................... 1 1.1 Aquaculture .................................................................................................... 1 1.2 Aquaculture industry importance .................................................................... 2 1.3 Australian aquaculture .................................................................................... 4 1.4 Sparid aquaculture .......................................................................................... 5 1.5 Broodstock as key to global aquaculture ......................................................... 6 1.6 Link between nutrition, body condition and reproductive physiology .............. 8 Dietary fatty acids .................................................................................... 9 Antioxidants .......................................................................................... 10 Blood biochemistry................................................................................ 11 1.7 Acanthopagrus butcheri ................................................................................ 13 1.8 Aims and objectives ...................................................................................... 15 2 Materials and methods ...................................................................................... 17 2.1 Aquaculture system ...................................................................................... 17 2.2 Fish capture and handling ............................................................................. 20 2.3 Feed trial ...................................................................................................... 21 2.4 Sample preparation ....................................................................................... 26 2.5 Condition analysis ........................................................................................ 27 2.6 Liver analysis ............................................................................................... 28 2.7 Statistical analysis ........................................................................................ 29 3 Results ............................................................................................................... 30 3.1 Nutritional composition of diets .................................................................... 30 3.2 Fish condition ............................................................................................... 36 3.3 Blood analysis .............................................................................................. 41 3.4 Liver analysis ............................................................................................... 48 4 Discussion .......................................................................................................... 57 4.1 Condition analyses ........................................................................................ 57 4.2 Blood biochemistry....................................................................................... 60 4.3 Liver analyses ............................................................................................... 63 5 Future Directions .............................................................................................. 66 6 Conclusions ...…………………………………………………………………… 68 7 References.......................................................................................................... 70 8 Appendix ........................................................................................................... 80 1 Introduction 1.1 Aquaculture Fishing for sustenance by humans has been documented as far back as 100,000 years ago (Walter et al., 2000), with fish consumption being historically important, stemming from religious beliefs and extending to consumption as a luxury food item (Fabinyi, 2012; Pauly, 2018). Aquaculture is a broad term for a variety of