Fish monitoring provides further insight into estuarine ecosystem resilience!
The estuarine fish monitoring program is revealing incredible insights into the importance of coastal habitats for fish and their response to disturbance, such as floods.
Find out more about it in this article written by our incredible Knowledge Research team.
With four years of data, we are gaining more evidence and improving our understanding of what drives estuarine fish distributions and the importance of coastal habitats in supporting ecosystem resilience. This depth of understanding has only been possible following multiple years of consistent monitoring underpinned by the development of an elegant conceptual framework to compare estuaries.
Fish monitoring has focused on a diversity of estuaries with different habitat configurations and catchment land-uses across South East Queensland (SEQ). This monitoring has also occurred in both high rainfall years characterised by major flooding (such as 2022) and in low rainfall years with minimal flooding (such as 2020).
The response and recovery of fish assemblages over this four-year period is providing new insights into how estuarine habitats contribute to whole of ecosystem resilience. This has been many years in the making and a range of knowledge gaps have now been addressed to lay the foundation for meaningful assessment of fish assemblages.
How are estuarine fish being monitored?
A fundamental challenge in establishing a long-term monitoring program for estuarine fish is in describing patterns in time and space in a repeatable manner. A related challenge is in comparing estuarine fish assemblages within estuaries or ‘management units’ that have fundamentally different attributes in a meaningful way.
For example, the Pumicestone Passage has a unique seascape, characterised by tidal distributary channels, extensive intertidal flats, seagrass meadows and fringing eucalyptus and mangrove forests. This is distinct from the Brisbane River estuary that is characterised by a relatively deep tidal channel, limited intertidal areas, no seagrass meadows and limited fringing vegetation.
To overcome this challenge, an elegant conceptual framework was developed to compare fish assemblages between estuaries (Gilby et al. in review). The basis of the framework is as follows; Are fish assemblages within individual estuaries (as quantified by biodiversity measures and the abundance of key indicator species) better or worse than would be predicted given patterns across the region, and how do these patterns vary between estuaries over time? Key indicators include species richness, and the abundance of sea mullet, estuary perchlet, yellowfin bream, luderick and Moses perch.
The predictive models used within this framework have also been developed with a good underlying ecological understanding of spatial and temporal divers of variation in key metrics (Conceptual diagram 1 below). With this framework established, we can now effectively monitor and report on changes in estuarine fish!
Exciting insights on ecosystem resilience!
The four years of monitoring now show which estuaries are performing well comparatively to others across SEQ. High performers include Tallebudgera, Tingalpa, Maroochy Mooloolah and Noosa estuaries, while the Albert, Brisbane and Logan estuaries have performed more poorly.
In 2022, there was a decline in estuarine fish assemblage diversity and abundance across SEQ estuaries as a result of major flood disturbance. Resurveys in 2023, ~18 months after the major floods of 2022, show that 11 out of the 13 estuaries have recovered, and six estuaries have achieved their highest grade since surveys began in 2020. There are many potential drivers of recovery over the medium term, including:
- The re-establishment of optimal environmental conditions that drive fish persistence within estuaries.
- The enhancement of available habitat and energy sources as a result of flood flows.
Interestingly, the estuaries with the highest performance in 2023 since surveys began (Maroochy, Nerang, Noosa, Pine, Pumicestone Passage and Tallebudgera Creek) either contain vast seagrass meadows within the estuary itself and/or the estuary is fed by a semi-enclosed embayment that contains vast seagrass meadows.
By contrast, recovery was typically not as strong in estuaries in poorer condition, including the Albert, Brisbane, and Logan estuaries. This suggests that floods lead to an enhancement of fish assemblages in the year following flooding, and this is most pronounced in estuaries with intact key habitats (Conceptual diagram 2 below).
Although more work is required to confirm this, this program is providing greater insight into what underpins ecosystem resilience in estuaries and the management actions can be taken to support it.
An impressive monitoring effort!
The long-term monitoring of estuarine fish in South East Queensland has been underway since 2020 through an impressive collaborative effort between Healthy Land & Water and the University of the Sunshine Coast (UniSC). With four years of surveys, the project now represents a significant body of work, with annual surveys comprised of up to 10 replicates of six estuarine habitats, (seagrass, mangroves, saltmarsh, unvegetated muds and sands, rocky outcrops and log snags) throughout 13 estuaries for n = 2440 sites in total and 628 sites in 2023.
Which estuaries are currently being monitored?
Estuaries currently being monitored as part of the program include the Albert, Brisbane, Caboolture, Logan, Maroochy, Mooloolah, Nerang, Noosa, Pimpama, Pine, Tallebudgera, and Tingalpa estuaries and the Pumicestone Passage.
Fast facts
- Seagrass is the most important habitat for supporting diverse and abundant fish assemblages in South East Queensland estuaries!
- Patterns established during the estuarine fish monitoring program are also being used to prioritise restoration actions.
- Estuary perchlet is by far the most abundant species in our estuaries, followed by yellowfin bream, southern herring and sea mullet.
- Greater connectivity with the estuary mouth and mangroves tend to be the most important variables driving higher fish abundance in estuaries. Dissolved oxygen and chlorophyll a concentration are also significant contributors.
- A barramundi was spotted in footage in a 2023 deployment! The first observation of this species on video.
How does this work inform ecosystem health reporting?
- Healthy Land & Water brings a large amount of information together as part of the official South East Queensland Report Card. Pulling together the information needed to inform the health of our region is only possible thanks to a large-scale coordinated effort. Healthy Land & Water leads this, in close collaboration with its members (see below for the long list of partners in the Report Card initiative). Together we pull together the multiple data sources that help paint a snapshot of waterway health and socio-economic benefits of waterways in South East Queensland. Estuarine fish monitoring site locations can be found on the Report Card interactive map website. Technical Reports can be made available through a request to
This email address is being protected from spambots. You need JavaScript enabled to view it. . - Some of the amazing videos captured by these surveys offer a rare glimpse into this underwater wonderland. Check USC Fish Ecology Research’s YouTube channel to check out some of the action. (https://www.youtube.com/channel/UCxiwYz6hes_f6iYhQKtx50w/feed).
Conceptual diagram 1
Conceptual diagram 2
References
Goodridge Gaines, L., Gilby, B., Henderson, C., Olds, A., Willis, C., Wills, E., Hay, E. 2024. South East Queensland estuarine fish surveys and reporting 2023. University of Sunshine Coast and Healthy Land and Water.
Goodridge Gaines, L.A., C.J. Henderson, J.D. Mosman, A.D. Olds, H.P. Borland, and B.L. Gilby. 2022b. Seascape context matters more than habitat condition for fish assemblages in coastal ecosystems. Oikos 2022: e09337.
Gilby, B.L., L.A. Goodridge Gaines, C.J. Henderson, H.P. Borland, J. Coates-Marnane, R.M. Connolly, P.S. Maxwell, J.D. Mosman, A.D. Olds, H.J. Perry, E. Saeck, and I. Tsoi. Under review. Optimising coastal fish monitoring and reporting through predicted versus observed abundance models. Marine Environmental Research.
Henderson, C.J., B.L. Gilby, E. Stone, H.P. Borland, and A.D. Olds. 2021. Seascape heterogeneity modifies estuarine fish assemblages in mangrove forests. ICES Journal of Marine Science 78: 1108-1116.