Oral Presentation Australian Society for Fish Biology Conference 2017

Facilitating passage to spawning habitat for an endangered percichthyid (#69)

Ben Broadhurst 1 , Mark Lintermans 1 , Dylan van der Meulen 2 , Rhian Clear 1
  1. University of Canberra, Canberra, ACT, Australia
  2. Department of Primary Industries, Fisheries Research - Freshwater Ecosystems, Narrandera, NSW, Australia

Reservoirs can serve as refuge habitats for endangered Macquarie perch Macquaria australasica, though this species requires access to the river habitats to spawn. Enlargement of Cotter Reservoir, Australian Capital Territory, has resulted inundation of existing riverine spawning grounds of the resident population of Macquarie perch. Natural barriers to passage have fragmented this population from spawning habitat, and for the first three years of filling there was recruitment failure, because of lack of access to suitable spawning habitat. The spawning movements of Macquarie perch (n = 40) were monitored using an acoustic array deployed at the head of the reservoir and in each pool upstream of perceived natural barriers. As expected, frequency of tagged adult Macquarie perch detected at the head of the reservoir and in the pools immediately upstream peaked from late October until early December (known spawning window of this species), when river temperatures exceeded 14.5 °C. Entry to the river by each individual was typically brief (minutes to hours), repeated across days and undertaken during low-light periods. A wet winter and spring meant that upstream reservoirs were largely operating unregulated and at higher discharge than regular releases from August until mid-December. These unregulated flows facilitated passage of tagged adult Macquarie perch to at least 500 m of river and past two instream barriers. Subsequent netting of the reservoir and river upstream of the reservoir revealed recruitment to juveniles of a magnitude similar to that of the pre-filling era, confirming passage past natural barriers to suitable spawning grounds. This study provides important information of the spawning movement ecology of this species critical to long-term survival.