Thesis
Investigating climate change impacts on whiting (Sillaginidae) off eastern Australia
Southern Cross University
Doctor of Philosophy (PhD), Southern Cross University
2024
DOI:
https://doi.org/10.25918/thesis.453
Metrics
Abstract
Anthropogenic climate change poses significant challenges to marine ecosystems, affecting many fish populations already strained by commercial and recreational fishing activity. Understanding climate impacts on harvested species contributes to sustainable fisheries management. Additionally, evaluating fish movement and connectivity across large spatial distributions is useful, yet challenging, for stock assessments. My thesis investigates the impacts of climate change on three economically-important species of whiting (Sillaginidae) in eastern Australia—sand whiting (Sillago ciliata), stout whiting (Sillago robusta), and eastern school whiting (Sillago flindersi). Different species combinations were used in each chapter, depending on fish availability. Mesocosm experiments with juvenile stout and sand whiting showed enhanced growth under ocean warming scenarios. Following the mesocosm experiment with juvenile stout whiting, body condition was measured using Bioelectrical Impedance Analysis and revealed that whiting had better body condition under ocean warming scenarios. A second mesocosm experiment with juvenile sand whiting revealed that fish growth was not affected by ocean acidification. To investigate connectivity and movement among wild trawl whiting populations, otolith oxygen isotopes (δ18Ootolith) were analysed for adult stout and eastern school whiting captured across their spatial distributions. Otolith oxygen isotopes were interpreted as natural tags and as indicators of water temperatures that an individual fish had experienced, due to the δ18Ootolith temperature-dependent fractionation relationships developed during mesocosm experiments. Otolith oxygen isotopes of wild-caught whiting indicated that juvenile trawl whiting primarily inhabit warmer nursery habitats before moving to cooler waters as adults. Dispersal mechanisms likely involve inshore-offshore ontogenetic migrations and utilisation of prevailing southward longshore currents. Results suggest a single biological stock for both species of trawl whiting but with distinct patterns of mixing amongst locations and possible sex-specific dispersal patterns for eastern school whiting, with males dispersing further than females. Detailed δ18Ootolith profiles obtained for wild-caught eastern school whiting, determined by Sensitive High Resolution Ion Micro Probe (SHRIMP) analysis, also revealed seasonal trends in δ18Ootolith values and validated otolith age determination. This method confirmed that δ18Ootolith maxima coincide with opaque increment formation on otoliths during cooler winter water temperatures. Overall, my thesis provides insight into how climate change may affect eastern Australian whiting species and demonstrates the utility of otolith isotopic signatures in understanding thermal preferences, movement and population dynamics of fishes.
Details
- Title
- Investigating climate change impacts on whiting (Sillaginidae) off eastern Australia
- Creators
- Melissa Hui Wen Tan
- Contributors
- Brendan Kelaher (Supervisor) - Southern Cross UniversityKarina Hall (Supervisor) - Southern Cross University
- Awarding Institution
- Southern Cross University; Doctor of Philosophy (PhD)
- Theses
- Doctor of Philosophy (PhD), Southern Cross University
- Publisher
- Southern Cross University
- Number of pages
- xviii, 345
- Identifiers
- 991013273511002368
- Copyright
- © Melissa H. W. Tan 2024
- Academic Unit
- Faculty of Science and Engineering; National Marine Science Centre
- Resource Type
- Thesis