Oral Presentation Australian Society for Fish Biology Conference 2024

Ungrateful Australian lungfish eating themselves out of house and home (110825)

Colin L Burke 1 , Luke Carpenter-Bundhoo 1 , David Roberts 2 , César Herrera 3 , Hannah Franklin 1 , Mark Kennard 1
  1. Australian River Institute, Griffith University, Nathan, QLD, Australia
  2. Seqwater, Ipswich, QLD, Australia
  3. Coastal and Marine Research Centre, Griffith University, Gold Coast, Queensland, Australia

Aquatic macrophytes, especially Vallisneria nana, provide essential spawning habitat and food resources for the threatened Australian lungfish (Neoceratodus forsteri). Large floods in the Brisbane River have dramatically reduced macrophyte habitat for lungfish and fragmentation by a dam has inhibited hydrochory (dispersal of propagules), and recovery. Active transplanting of macrophytes can be a viable restoration option, however, newly replanted beds may not persist due to environmental factors or grazing by herbivorous lungfish. In this study, we analysed the effects of environmental conditions on growth and expansion of transplanted V. nana in herbivore exclosures in the mid-Brisbane River. We also quantified the impact of aquatic herbivores on different patch sizes (15m2 – 60m2) of restored V. nana to test if larger macrophyte beds confer greater resistance to grazing using a paired control/treatment design. Macrophyte replanting in fenced exclosures was highly successful, with dense beds rapidly establishing to >70% cover within 160 days. However, experimental exposure to grazing significantly reduced macrophyte cover and complete removal of exclosure fencing resulted in rapid and complete loss. Our findings suggest that transplanting is a viable aquatic macrophyte restoration method with exclusion of grazing, which is critical for creating resistant beds to disturbances and driving future macrophyte recovery.