Westport has partnered with the Western Australian Marine Science Institution (WAMSI) to deliver the $13.5 million WAMSI-Westport Marine Science Program. This 3-year program is developing the latest data, information and modelling on the complex environmental systems and community values associated with Cockburn Sound.
Project 4.2.3: Trophic pathways and food web structure of Cockburn Sound and Owen Anchorage
Research theme: Fisheries and Aquatic Resources
Researchers: J Tweedley, D Cox, M Haywood, K Krispyn, G Hyndes, R McCallum, L Beltran, J Billinghurt and D Johnston.
Publication date: May 2025
Understanding the food web and trophic pathways within Cockburn Sound
Cockburn Sound supports a diverse range of flora and fauna. These species and the biological communities are all part of a complex food web, providing nutrients to the differing trophic levels, with fish and apex predators at the higher end of the food chain.
This study looked to understand the food web and flow of nutrients within Cockburn Sound, which will inform how proposed development or resilience building activities could impact the complex ecosystem.
The study used three main data sources for the project:
- The gut contents of 2,117 fish and invertebrates from 18 species, providing high-resolution data on the last meal of an individual animal.
- Stable isotope ratios for the δ13C and δ15N signatures for nine primary ‘producers’ and 55 ‘consumers’, ranging from detritivores (an animal that feeds on dead organic manner) to apex predators. These isotopes show the assimilation of material from food sources over periods of weeks to months.
- Relevant scientific literature
What the study found
- Many species had a variable and wide-ranging diet, largely influenced by their body morphology (e.g. mouth structure and size).
- The dietary composition of most species differed with increasing body size, with larger predators consuming larger and more mobile prey.
- There were regional and seasonal differences in diet across most species, with the diets of individuals caught from Owen Anchorage typically being the most distinct.
- Benthic invertebrates, particularly decapods like crabs and prawns, stomatopods (mantis shrimp) and bivalve molluscs, were consumed frequently and in large volumes, indicating they are an important food source for many fish species, especially more specialist feeders.
What the report recommended
The research has developed a comprehensive data set on the dietary composition and trophic level for more than 200 of the fish species in Cockburn Sound. This data can be used in ecosystem models to help predict the impacts of the proposed or future infrastructure developments and climate change on trophic linkages and the flow of nutrients.
How Westport will use this report
Westport will use this report to inform its dredging and environmental management strategies for the port development, with the intent of supporting the long-term health of Cockburn Sound.
You can read the full report here.
