Project number:
2020-003
Project Status:
Current
Budget expenditure:
$161,550.00
Principal Investigator:
Adam Miller
Organisation:
Deakin University Geelong Waurn Ponds Campus
Project start/end date:
29 May 2020
-
29 Sep 2022
Contact:
FRDC
SPECIES
Rock Flathead supports commercial mesh-net fisheries in Corner Inlet; however, CPUE for this fishery has shown a declining trend since 2005, while remaining above the management reference point. The stock structure of rock Ffathead in Victorian waters is largely unknown, presenting uncertainty for fishers and managers when assessing the future of the fishery and ensuring the sustainability of the stock.
1. Determine the population structure of rock flathead in south-eastern Australia, with emphasis on understanding how the Corner Inlet population relates to other populations
2. Characterise the movement and residency patterns of rock flathead in Corner Inlet
Final report
ISBN:
978-0-7300-0236-9
Authors:
Justin Rizzari
Darren Wong
Madeline Toomey
Ty Matthews
Kay Critchell
Samantha Sherman
Simon Conron
James Haddy
Paul Hamer
Johnathon Davey
Adam Miller
Final Report
•
2024-11-30
•
1.96 MB
2020-003-DLD.pdf
Rock Flathead (Platycephalus laevigatus) is a marine fish that inhabits shallow seagrass habitats across southern Australia, with a distribution extending from Greenwell Point in New South Wales to Geographe Bay in Western Australia, including Tasmania. The species supports recreational fisheries across its range, and a single commercial fishery in Corner Inlet in eastern Victoria. Commercial catches of Rock Flathead from Corner Inlet declined significantly between the mid and late 1990s, with catches dropping from 92 tonnes to 30 tonnes over a 5-year period (Koopmen et al. 2004).
This project aimed to adopt an integrated approach, involving population genomics, otolith micro-chemistry, and acoustic telemetry, to address key questions regarding patterns of biological connectivity among Rock Flathead fishing stocks, with a specific focus on the fishery at Corner Inlet. Specific questions addressed include:
1. Is the Corner Inlet Rock Flathead population an isolated, self-replenishing stock or not?
2. If not, what is the broader population structure and connectivity of Rock Flathead in south-east Australia, and how does the Corner Inlet population relate to other populations?
3. How do movement behaviours, both within Corner Inlet and between Corner Inlet and coastal waters, influence population and fishery dynamics?
We found consistent results across all survey methods, pointing to limited fish movement between Corner Inlet and stocks outside the inlet. Specifically, analyses of population genetic structure indicated significant genetic structuring and gene flow limitations across the sampling distribution that included Victorian and Tasmanian embayment and open coastal habitats, indicating the Corner Inlet Fishery to be an isolated gene pool and genetically distinct from all other stocks. Similarly, analyses of otolith micro-chemistry suggested chemical profiles of fish from Corner Inlet to be distinct from all other sample locations from south-eastern Australia, indicating restricted dispersal across both juvenile and adult life stages. Finally, acoustic telemetry indicated individual fish movements to be highly localised, with movements between Corner Inlet fish and other locations being unlikely. Although data obtained from acoustic telemetry was limited due to detections from limited individuals and unexpected loss of receivers, our weighted evidence approach suggests that the Corner Inlet Rock Flathead fishery is an isolated, self-recruiting stock, which requires independent management consideration.
This project aimed to adopt an integrated approach, involving population genomics, otolith micro-chemistry, and acoustic telemetry, to address key questions regarding patterns of biological connectivity among Rock Flathead fishing stocks, with a specific focus on the fishery at Corner Inlet. Specific questions addressed include:
1. Is the Corner Inlet Rock Flathead population an isolated, self-replenishing stock or not?
2. If not, what is the broader population structure and connectivity of Rock Flathead in south-east Australia, and how does the Corner Inlet population relate to other populations?
3. How do movement behaviours, both within Corner Inlet and between Corner Inlet and coastal waters, influence population and fishery dynamics?
We found consistent results across all survey methods, pointing to limited fish movement between Corner Inlet and stocks outside the inlet. Specifically, analyses of population genetic structure indicated significant genetic structuring and gene flow limitations across the sampling distribution that included Victorian and Tasmanian embayment and open coastal habitats, indicating the Corner Inlet Fishery to be an isolated gene pool and genetically distinct from all other stocks. Similarly, analyses of otolith micro-chemistry suggested chemical profiles of fish from Corner Inlet to be distinct from all other sample locations from south-eastern Australia, indicating restricted dispersal across both juvenile and adult life stages. Finally, acoustic telemetry indicated individual fish movements to be highly localised, with movements between Corner Inlet fish and other locations being unlikely. Although data obtained from acoustic telemetry was limited due to detections from limited individuals and unexpected loss of receivers, our weighted evidence approach suggests that the Corner Inlet Rock Flathead fishery is an isolated, self-recruiting stock, which requires independent management consideration.
