ResearchOnline@JCU This file is part of the following reference: Lloyd, Julie Anne (2006) Demography of Pristipomoides multidens in northern Australia and a comparison within the Family Lutjanidae with respect to depth. PhD thesis, James Cook University. Access to this file is available from: http://researchonline.jcu.edu.au/31598/ The author has certified to JCU that they have made a reasonable effort to gain permission and acknowledge the owner of any third party copyright material included in this document. If you believe that this is not the case, please contact [email protected] and quote http://researchonline.jcu.edu.au/31598/ Demography of Pristipomoides multidens in northern Australia and a comparison within the Family Lutjanidae with respect to depth Thesis submitted by Julie Anne Lloyd BSc in December 2006 For the degree of Doctor of Philosophy in Marine Biology within the School of Marine Biology and Aquaculture James Cook University Statement of Access I, the undersigned, the author of this thesis, understand that James Cook University will make this thesis available for use within the University Library and, via the Australian Digital Theses network (unless granted an exemption), for use elsewhere. I understand that, as an unpublished work, a thesis has significant protection under the Copyright Act and; I do not wish to place any further restriction on access to this work. July 2010 Julie Anne Lloyd Electronic Copy I, the undersigned, the author of this work, declare that the electronic copy of this thesis provided to James Cook University Library is an accurate copy of the print thesis submitted, within the limits of the technology available. July 2010 Julie Anne Lloyd Statement on Sources Declaration I declare that this thesis is my own work and has not been submitted in any form for another degree or diploma at any university or other institution of tertiary education. Information derived from the published or unpublished work of others has been acknowledged in the text and a list of references is given. July 2010 Julie Anne Lloyd Statement on the Contribution of Others Nature of Assistance Contribution Names, Titles and Affiliations of Co-contributors Intellectual support Editorial assistance Dr Andria Handley (NT Department of Resources) Statistical support Dr Mark Hearnden ((NT Department of Resources) Financial support Purchase of fish samples ACIAR project FIS97/165 Laboratory materials ACIAR project FIS97/165 Preparation of histology ACIAR project FIS97/165 sections Technician’s wages ACIAR project FIS97/165. Annual airfare to NT Department of Resources Townsville Data collection Indonesian otolith R. Andamari from Gondol Research Station for samples and data Coastal Fisheries Indonesia (ACIAR project FIS97/165) Dr David Milton, Mr Gary Fry (CSIRO) (ACIAR project FIS97/165) Technical support Laboratory preparation of Chris Errity, Chris Tarca, Charles Bryce (NT otoliths Department of Resources) Preparation of histology Ms Cheryl Day (NT Department of Resources) sections Edge analysis of otoliths Dr Lou (James Cook University) Acknowledgements I would like to take this opportunity to thank the many people who have helped my during the years I undertook this thesis part-time. Firstly, I would like to thank my supervisor Prof Howard Choat, for his insightful suggestions, guidance and patience. Special thanks also to my colleagues at NT Fisheries for both practical and moral support; especially Rik Buckworth, Roland Griffin, Andria Handley and Julie Martin for much needed encouragement, kindly reading thesis drafts and providing a sounding board for discussion of ideas. Many thanks to Mike Mackie (WA Department of Fisheries) for reading the reproductive chapter (Chapter 4) and on-going encouragement. Thanks also to Chris Errity, Chris Tarca, Stephanie Boubaris, Mike Elmsley, Cheryl Day and Charles Bryce for their valuable technical support, to Mark Hearnden for statistical support, and to the NT Timor Reef fishers who provided goldband samples from the Timor Sea and Bill Passey for providing the Arafura Sea samples. Special thanks to Andria Handley for rescuing me from my formatting “muddle” and also providing valuable editorial assistance. To Brigid Kerrigan, Mark McCormack and Jean Collins, thank you for your generosity in providing accommodation during my visits to Townsville. I would like to acknowledge NT Department of Resources (Fisheries) for their financial assistance in providing an annual air fare to Townsville and study leave. Funding for the research undertaken in this thesis was largely provided the Australian Centre for International Agricultural Research as part of a collaborative project between, CSIRO, v Northern Territory, Queensland and Indonesia to investigate the shared snapper fisheries in northern Australia and eastern Indonesia (ACIAR FIS97/165). Finally, I would like to thank my children Shauna, Vanessa and Paul Mounsey for the love, support and encouragement they have given me during my studies. vi Abstract Lutjanids are an important group of perciform reef fish distributed over a wide depth range throughout the world’s tropical and sub tropical oceans. It has been noted by Newman and Williams (1996) that within this complex there is a separation of genera with respect to depth. Shallower waters <100 m are dominated by the genera Lutjanus, Aprion, Macolor, Symphorichthys, and Symphorus , while in the intermediate depths (100-200 m) Pristipomoides, and Paracaesio dominate, and in the deeper waters >200 m Etelis are more prevalent. Therefore the lutjanid complex offers a unique opportunity to observe whether there is a distinction in life history characteristics of genera within the same family with respect to different depth zones and consequently different environmental influences. While many shallow water species have been well studied, there is a paucity of information on species in the intermediate and deeper waters where research is expensive and logistically difficult. The lack of information is a significant problem for many developing countries for which lutjanids are an important source of export revenue as well as food. In developed countries, attracting funding for small-scale “boutique” fisheries is very difficult, despite the recognised need to manage all fisheries in a sustainable manner. Therefore, in the absence of research data, managers and scientists are forced to use proxy values, but how valid is this approach? To examine this question, I undertook a comparison of the demography of genera within the Family Lutjanidae within different depth ranges; shallow (<100 m), intermediate (100-200 m) and deep (>200 m). I conducted a detailed study of Pristipomoides multidens (intermediate depth range) and compared findings from this vii study with information published for lutjanids from other depth ranges. This provided a framework within which to assess whether it is acceptable to use proxy values, and whether proxy values should preferentially be from lutjanids inhabiting the same locality possibly from different depth ranges, or the same depth range even if the information is from a different region. The key findings were: Significant differences are evident in age, growth and reproductive parameters for genera from the different depth ranges. Small shallow water lutjanids appear to show greater variability in growth across smaller scales compared species in intermediate and with deeper waters. A possible explanation for this observation may relate to the tendency for small lutjanids to be more reef-associated and hence their growth more strongly influenced by localised conditions compared with lutjanids in intermediate and deep waters. The lutajnids ( Pristipomoides multidens , Lutjanus malabaricus and L. erythropterus ) in my study showed a general trend for a greater mean length at age for the Timor Sea when compared with the Arafura Sea. Likewise, my results showed, longevity (defined by the upper 20% of ages for a species) was also greater for fish from the Timor Sea when compared with those from the Arafura Sea. This is possibly due to the differences in depth as the Arafura Sea is considerably shallower than the Timor Sea. Samples taken from the Arafura Sea were caught at the 50-60 m depth range, while samples from the Timor Sea were taken in the 100-150 m depth range. However, fishing gear selectivity may confound these observed differences. Samples from the Arafura Sea were taken by trawling, and it is possible that larger, stronger fish may be able to swim viii faster than the trawled nets and therefore avoid capture. Timor Sea samples were taken by trap and dropline methods. Lutjanids appear to exhibit different spawning patterns with respect to depth zonation. Shallow water lutjanids favour a restricted summer peak in spawning activity, compared with lutjanids inhabiting intermediate and deeper waters, which appear to show a more protracted spawning season with a peak in activity during summer months and in some regions two spawning peaks are observed. In my study, I observed a protracted summer spawning period for P. mutidens , which was consistent with findings for this species by Brouard and Grandperrin (1985), and P. filamentosus (Kikkawa 1984). By comparing the results from my detailed study of P. multidens with lutjanids from other depth ranges I explored the validity of using proxy values for fisheries management for data-poor situations, and concluded that caution is needed in using proxy values from other lutjanids in stock assessment