Standard Presentation (15 mins) - Edits Required Australian Marine Sciences Association 2022

Revealing large-bodied fish use of critical estuarine habitat, using an imaging sonar. (#295)

Mark A Bennett 1 , Megan J Huggett 1 2 , Allistair Becker 3 , Matt D Taylor 3 , Troy F Gaston 1
  1. School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
  2. Centre for Marine Ecosystems Research, School of Science, Edith Cowan University, Joondalup, WA, Australia
  3. Fisheries Research, NSW Department of Primary Industries, Port Stephens, NSW, Australia

Although the productivity of estuarine wetlands is directly linked to the aerial extent of available habitat, there has still been considerable decline in wetland areal extant over the past 100 years. It is well understood that saltmarsh is a valuable habitat, particularly for many commercially and recreationally significant juvenile fish. However, how large-bodied fish use these systems is poorly understood due to the challenges associated with sampling turbid systems using traditional methods. Here we used an imaging sonar to census large-bodied fish activity in two estuaries with repairing saltmarsh. The imaging sonar, which uses sound waves to create free flowing video-like images through the water column, allows fish to be observed, measured and their direction of travel inferred. Results show that significant numbers and biomass of large-bodied fish visit these habitats. A small floodgate accessing a repairing wetland, less than 10 m wide, recorded upwards of 100 kg fish h-1, whereas a wider channel accessing a repairing saltmarsh, approximately 20 m in width, recorded over 250 kg fish h-1. These results demonstrate the capability of the imaging sonar for censusing fish in these turbid systems, but more importantly, it shows saltmarsh habitats are valuable to large-bodied fish.