Dynamic Distributions of Coastal Zooplanktivorous Fishes
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Dynamic distributions of coastal zooplanktivorous fishes Matthew Michael Holland A thesis submitted in fulfilment of the requirements for a degree of Doctor of Philosophy School of Biological, Earth and Environmental Sciences Faculty of Science University of New South Wales, Australia November 2020 4/20/2021 GRIS Welcome to the Research Alumni Portal, Matthew Holland! You will be able to download the finalised version of all thesis submissions that were processed in GRIS here. Please ensure to include the completed declaration (from the Declarations tab), your completed Inclusion of Publications Statement (from the Inclusion of Publications Statement tab) in the final version of your thesis that you submit to the Library. Information on how to submit the final copies of your thesis to the Library is available in the completion email sent to you by the GRS. Thesis submission for the degree of Doctor of Philosophy Thesis Title and Abstract Declarations Inclusion of Publications Statement Corrected Thesis and Responses Thesis Title Dynamic distributions of coastal zooplanktivorous fishes Thesis Abstract Zooplanktivorous fishes are an essential trophic link transferring planktonic production to coastal ecosystems. Reef-associated or pelagic, their fast growth and high abundance are also crucial to supporting fisheries. I examined environmental drivers of their distribution across three levels of scale. Analysis of a decade of citizen science data off eastern Australia revealed that the proportion of community biomass for zooplanktivorous fishes peaked around the transition from sub-tropical to temperate latitudes, while the proportion of herbivores declined. This transition was attributed to high sub-tropical benthic productivity and low temperate planktonic productivity in winter. As temperatures declined in autumn, zooplanktivores migrated away from reefs, likely seeking warmer waters offshore. This was supported in a related bioacoustics survey around Montague Island, southern NSW, which showed the coast-to-shelf distribution of pelagic zooplanktivores in early spring was closely correlated with temperature, with schools seeking warmer waters of the East Australian Current at the shelf edge. Some zooplanktivores may select warm water to improve physiological performance and may also avoid shallow coastal areas, where vertically constrained distribution increases predation risk. To examine spatiotemporal dynamics of zooplanktivores around coastal reefs a non-scientific portable multibeam echosounder was deployed. As calibration of such instruments is impracticable, I assessed a novel metric of school thickness, delineating the spatial boundaries of schools rather than quantifying backscatter. These methods were applied to study school distribution around natural and artificial reefs, and variability attributed to current exposure and time of day. Schools regularly distributed upstream of structure, as fish competed for access to un-grazed prey. Schools blanketed the seafloor at night and rose high in the water column during the day to feed, particularly around high vertical https://gris.unsw.edu.au/alumni/ 1/2 4/20/2021 GRIS relief artificial structures. These observations can inform the design of artificial reefs to include high vertical relief to facilitate foraging in the water column. These findings also agree with observations of dense schools associated with offshore oil and gas infrastructure and provide support for leave-in-place decommissioning. These distribution patterns have important implications for fisheries and for the predators which depend on regular and predictable access to prey. Zooplanktivorous fishes are an essential trophic link transferring planktonic production to coastal ecosystems. Reef-associated or pelagic, their fast growth and high abundance are also crucial to supporting fisheries. I examined environmental drivers of their distribution across three levels of scale. Analysis of a decade of citizen science data off eastern Australia revealed that the proportion of community biomass for zooplanktivorous fishes peaked around the transition from sub-tropical to temperate latitudes, while the proportion of herbivores declined. This transition was attributed to high sub-tropical benthic productivity and low temperate planktonic productivity in winter. As temperatures declined in autumn, zooplanktivores migrated away from reefs, likely seeking warmer waters offshore. This was supported in a related bioacoustics survey around Montague Island, southern NSW, which showed the coast-to-shelf distribution of pelagic zooplanktivores in early spring was closely correlated with temperature, with schools seeking warmer waters of the East Australian Current at the shelf edge. Some zooplanktivores may select warm water to improve physiological performance and may also avoid shallow coastal areas, where vertically constrained distribution increases predation risk. To examine spatiotemporal dynamics of zooplanktivores around coastal reefs a non-scientific portable multibeam echosounder was deployed. As calibration of such instruments is impracticable, I assessed a novel metric of school thickness, delineating the spatial boundaries of schools rather than quantifying backscatter. These methods were applied to study school distribution around natural and artificial reefs, and variability attributed to current exposure and time of day. Schools regularly distributed upstream of structure, as fish competed for access to un-grazed prey. Schools blanketed the seafloor at night and rose high in the water column during the day to feed, particularly around high vertical relief artificial structures. These observations can inform the design of artificial reefs to include high vertical relief to facilitate foraging in the water column. These findings also agree with observations of dense schools associated with offshore oil and gas infrastructure and provide support for leave-in-place decommissioning. These distribution patterns have important implications for fisheries and for the predators which depend on regular and predictable access to prey. https://gris.unsw.edu.au/alumni/ 2/2 4/20/2021 GRIS Welcome to the Research Alumni Portal, Matthew Holland! You will be able to download the finalised version of all thesis submissions that were processed in GRIS here. Please ensure to include the completed declaration (from the Declarations tab), your completed Inclusion of Publications Statement (from the Inclusion of Publications Statement tab) in the final version of your thesis that you submit to the Library. Information on how to submit the final copies of your thesis to the Library is available in the completion email sent to you by the GRS. Thesis submission for the degree of Doctor of Philosophy Thesis Title and Abstract Declarations Inclusion of Publications Statement Corrected Thesis and Responses 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. COPYRIGHT STATEMENT I hereby grant the University of New South Wales or its agents a non-exclusive licence to archive and to make available (including to members of the public) my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known. I acknowledge that I retain all intellectual property rights which subsist in my thesis or dissertation, such as copyright and patent rights, subject to applicable law. I also retain the right to use all or part of my thesis or dissertation in future works (such as articles or books). For any substantial portions of copyright material used in this thesis, written permission for use has been obtained, or the copyright material is removed from the final public version of the thesis. AUTHENTICITY STATEMENT I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. https://gris.unsw.edu.au/alumni/ 1/2 4/20/2021 GRIS Welcome to the Research Alumni Portal, Matthew Holland! You will be able to download the finalised version of all thesis submissions that were processed in GRIS here. Please ensure to include the completed declaration (from the Declarations tab), your completed Inclusion of Publications Statement (from the Inclusion of Publications Statement tab) in the final version of your thesis that you submit to the Library. Information on how to submit the final copies of your thesis to the Library is available in the completion email sent to you by the GRS. Thesis submission for the degree of Doctor of Philosophy Thesis Title and Abstract Declarations Inclusion of Publications Statement Corrected Thesis and Responses 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 the candidate's