Fish of the Perth Hills


Suzanne Thompson, an Environmental Officer at the Department of Biodiversity, Conservation and Attractions, started her talk with a video taken downstream of the Canning Dam. It showed the various fish we have in the dams, remnant pools and streams of the Canning River and Helena valley areas. She explained what habitats and food sources fish like in the Perth Hills’ waterways and described the threats to and management of the local rivers. In discussing this, Suzy brought the impact of climate change to life.

Suzanne provided information on four of our small native freshwater species. The best place to look for these tiny fish is amongst large woody debris, emergent vegetation, overhanging vegetation and undercut banks. The status of these fish is common but declining. This is due to salinity, eutrophication (caused by excessive richness of nutrients) and predation by introduced fish species.

Western Pygmy Perch (Nannoperca vittata)
(provided live in a small aquarium for the audience to see):

  • Size – males 5cm, females 8cm.
  • Mottled golden-brown. Males more brilliantly coloured in breeding season with golden mottling and a red-orange belly.

Western Minnow (Galaxias occidentalis)

  • Size – to 19 cm.
  • Long, slender fish, dark bars on sides and white belly.

Nightfish (Bostockia porosa)

  • Size – to 17cm.
  • Resembles a small Murray Cod. Olive-brown to black.

Freshwater Cobbler (Tandanus bostocki)

  • Size – to 50cm.
  • Mottled dark brown with barbels on snout.

Other species mentioned which are found in the Perth Hills:

Swan River Goby (Pseudogobius olorum).

Smooth Marron (Cherax cainii).

Gilgie (Cherax quinquecarinatus).

Carters Freshwater Mussel (Westralunio carteri).

Suzanne shared pictures and information about many introduced species and aquarium releases. These fish have voracious appetites, and are taking over the habitats and food sources of our native fish:

Exotic Mosquito Fish (Gambusia holbrooki).

One-spot Livebearer (Phalloceros caudimaculatus).

Redfin Perch (Perca fluviatilis).

Goldfish (Carassius auratus).

Yabby (Cherax destructor).

Eastern States Catfish (Tandanus tandanus).

Pearl Cichlid (Geophagus brasiliensis).

Suzanne collects information on the welfare of our native fish and monitors the introduced species that threaten them. Threats to the small native fish are many, including our drying climate, dams, water abstraction for Water Corporation licences, artificial barriers, and increasing sedimentation of river pools. Her talk included a graph of the impact of lower rainfall and reduced stream flow into our dams since the 1970s. Suzy is responsible for e-flow to regulate the river system by releasing dam water to maintain habitats and encourages reporting of illegal fishing to FISHWatch 1800 815 507.

The talk was extremely informative, and the audience were captivated by Suzanne’s knowledge base. She stayed and answered many questions from visitors and members of all ages.

Arlene Quinn

Reference sources:

A Field Guide to Freshwater Fishes, Crayfishes and Mussels of SW Australia, by Morgan, Beatty, Klunzinger, Allen & Burnham. ISBN 978-0-9871-644-0-7. Available from SERCUL.

Handouts from South East Regional Centre for Urban Landcare Freshwater Fish Group, Fish Health Unit Murdoch University, and Swan River Trust.