Habitat and Spatial Ecology of Two Iconic Estuarine Fishes Using
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Habitat and spatial ecology of two iconic estuarine fishes using acoustic telemetry Ruan Gannon February 2016 Evolution and Ecology Research Centre School of Biological, Earth and Environmental Sciences University of New South Wales A thesis in fulfilment of the requirements for the degree of Doctor of Philosophy THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Gannon First name: Ruan Other name/s: Abbreviation for degree as given in the University calendar: PhD School: School of Biological, Earth and Faculty: Science Environmental Sciences Title: Habitat and spatial ecology of two iconic estuarine fishes using acoustic telemetry Fishing, urbanisation and climate change all contribute to ecosystem change. Despite these substantial pressures, little is known about the ecology of many estuarine fish populations throughout eastern Australia. Two contrasting estuarine fishes were selected in this study, for their iconic status, varying degree of estuary use, and the dearth of information on their basic biology and ecology throughout their distribution. Acoustic telemetry was used to investigate the home range, habitat use and movement patterns of yellowfin bream Acanthopagrus australis, and dusky flathead Platycephalus fuscus. Space use for yellowfin bream was not related to fish length; although movement of each fish increased with fish length and decreased with water conductivity. The distance between tagged fish and mangrove habitat was correlated with time-of-day and tide level with fish moving closer to mangroves during the daytime and on high tides. The fine-scale movements and space use of acoustically tagged dusky flathead revealed relative movement was significantly related to fish size, tide and time of day. Space use was also positively correlated with fish size with two larger fish using multiple core areas of the estuary. Coupling spatial and relative movement trends with changes in prey mobility suggested an ontogenetic shift in foraging pattern for flathead. To assess factors influencing circadian rhythm of flathead, accelerometers evaluated activity of free ranging fish in relation to environmental parameters. Key factors influencing the activity rhythms of flathead were diel and tidal cycles; with an overarching influence of temperature. Previous studies show that ectotherm performance increases with temperature to an optimum, and subsequently declines. We used accelerometers near the middle of a species geographical distribution and gill-net catch data near the species latitudinal extremes to quantify temperature-related activity levels of flathead. Acceleration data approximated a thermal performance curve, with activity peaking at 23°C but declining rapidly at higher temperatures. Gill-net catch data displayed a similar trend, with a temperature-associated increase and decrease in catch rates in temperate and tropical regions, respectively. These data highlight the influence of temperature on ectotherm performance, and how thermal performance limits may shape a species geographic range. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). …………………………………………………………… ……………………………………..……………… ……….……………………...…….… Signature Witness Signature Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: INCLUSION OF PUBLICATIONS STATEMENT UNSW is supportive of candidates publishing their research results during their candidature as detailed in the UNSW Thesis Examination Procedure. Publications can be used in their thesis in lieu of a Chapter if: The student contributed greater than 50% of the content in the publication and is the “primary author”, ie. the student was responsible primarily for the planning, execution and preparation of the work for publication The student has approval to include the publication in their thesis in lieu of a Chapter from their supervisor and Postgraduate Coordinator. The publication is not subject to any obligations or contractual agreements with a third party that would constrain its inclusion in the thesis Please indicate whether this thesis contains published material or not. This thesis contains no publications, either published or submitted for publication ☐ (if this box is checked, you may delete all the material on page 2) Some of the work described in this thesis has been published and it has been ☒ documented in the relevant Chapters with acknowledgement (if this box is checked, you may delete all the material on page 2) This thesis has publications (either published or submitted for publication) ☐ incorporated into it in lieu of a chapter and the details are presented below CANDIDATE’S DECLARATION I declare that: I have complied with the Thesis Examination Procedure where I have used a publication in lieu of a Chapter, the listed publication(s) below meet(s) the requirements to be included in the thesis. Name Signature Date Ruan Gannon ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed …………………………………………….............. Date …………………………………………….............. COPYRIGHT STATEMENT ‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed …………………………………………….............. Date …………………………………………….............. AUTHENTICITY STATEMENT ‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’ Signed …………………………………………….............. Date …………………………………………….............. ii Abstract Fishing, urbanisation and climate change all contribute to ecosystem change. Despite these substantial pressures, little is known about the ecology of many estuarine fish populations throughout eastern Australia. Two contrasting estuarine fishes were selected for assessment of biotic and abiotic factors influencing their space use, movement and behaviour. The two species studied in this thesis were chosen for their iconic status, varying degree of estuary use, and the lack of information on their fine- scale movements and ecology throughout their distribution. Acoustic telemetry was used to investigate the home range, habitat use and movement patterns of yellowfin bream Acanthopagrus australis, and dusky flathead Platycephalus fuscus. Space use for yellowfin bream was not related to fish length; although movement (Minimum Activity Index, MAI, m h-1) of each fish increased with fish length and decreased with water conductivity. The distance between tagged fish and mangrove habitat was correlated with time-of-day and tide level with fish moving closer to mangroves during the daytime and on high tides. Patterns in fish movement and space use revealed behavioural responses of yellowfin bream to environmental fluctuations and highlighted the conservation value of small patches of estuarine habitats. The fine-scale movements and space use of acoustically tagged dusky flathead revealed relative movement was significantly related to fish