Deep Fish in Shallow Water
I come from Yamba in New South Wales; growing up in a coastal community, where the ocean and estuaries are heavily fished, has given me a passion to make a tangible contribution to conservation and environmental management aimed at having healthy populations of fish for all to enjoy into the future. I am also a long-suffering supporter of the Newcastle Knights and have a keen interest in sport more widely (e.g. Rugby League, Cricket, Soccer, Ice Curling) and music (playing the guitar).
Conventional wisdom holds that fish prefer complex structures over a variable seafloor (e.g. one often finds more fish in and around coral and rocky reefs over rough ground than on sandflats). Surprisingly, the role of water depth for fish is not well understood in shallow systems.
Because humans are deepening estuaries through dredging, there is an applied aspect to understanding how fish react to changes in depth of their preferred habitat – a ‘deep fish question’. It is plausible that human changes to channel dimensions and depths may change how fish use different types of habitats at different depths -this is I what I have set out to test.
My research investigates how the depth of different habitat types can affect the distribution, abundance and diversity of fish in estuaries, and if modification of depths by human activity can change the number and type of fish species that people like to catch and eat. I use two complementary approaches for this: 1.) I deploy underwater cameras to ‘sample’ the number and types of fish that occur in different habitats in different parts of estuaries, and 2.) I conduct fine-grained sonar surveys to create very detailed charts of estuaries (what we call bathymetry). This combination technique provides data to model how the interplay between water depth and habitat characteristic determine fish distributions and hence provides more accurate ways to plan for conservation of high-value habitats.