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Get to know some River Torrens / Karrawirra Pari fish

Monday 06 November 2023 | 4 min read

There are some loved, and not-so-loved fish in the River Torrens / Karrawirra Pari. Know the difference between Adelaide’s native and pest fish found in the river.

flatheaded gudgeon-credit Jeremy Gramp
A flatheaded gudgeon. Photo: Jeremy Gramp.

The River Torrens / Karrawirra Pari – the soul of our city – is the most prominent river in Adelaide and is of immense importance to Kaurna people.

It’s been the focus of a heap of work to ensure it remains healthy – including the Urban River Torrens Recovery Project, which kicked off in 2014.

This project aims to improve water quality along the river through things like removing weeds and revegetating with native plants.

Before the Urban River Torrens Recovery Project began, native fish numbers in the river had declined.

Thanks to the addition of fish ladders (structures to help fish get up over artificial barriers like weirs), the introduction of environmental water provisions – essentially water allocated to nature – and improved water quality, we’ve seen native fish start to thrive.

Here's 3 of our native resident fish:

Western blue-spot goby (Pseudogobius olorum)-credit Jeremy Gramp
Western blue-spot goby. Photo: Jeremy Gramp.

1. Western blue-spot goby

The western blue-spot goby (Pseudogobius olorum) is native to the River Torrens / Karrawirra Pari.

Blue-spot gobies are carnivorous – that is, meat-eaters. They get their name from the blue spot on the fin that is in the middle of their back, known as the dorsal fin.

They’re a small fish that generally grows up to 4 cm long, but can make it to a maximum of 6 cm.

They have their babies during autumn and spring, laying their eggs on water plants.

Flat-headed gudgeon. Photo: Jeremy Gramp.
Flat-headed gudgeon. Photo: Jeremy Gramp.

2. Flat-headed gudgeon

Another native to the River Torrens / Karrawirra Pari is the flat-headed gudgeon (Philypnodon grandiceps).

Known by many names, such as the big-headed gudgeon and bull-headed gudgeon, this fish commonly only grows to around 9 cm in length – which hardly warrants its big-headed nickname! This fish can reach 13 cm though – but you’ll still have to squint quite hard to spot them in the Torrens!

Adding to the challenge – they tend to hang out on the bottom of fresh and briny waterways, and in dense plants.

Despite their small size, they will actually feast on other little fish, as well as insects and crustaceans, which is the family of water creatures that includes crabs and shrimps.

This little native fish breeds in summer and spring in Adelaide. Their babies take 4 to 6 days to hatch and are roughly 3.8 mm in length!

Dwarf flatheaded gudgeon. Photo: Jeremy Gramp.
Dwarf flatheaded gudgeon. Photo: Jeremy Gramp.

3. Dwarf flat-headed gudgeon

Only found in Australia, the dwarf flathead gudgeon (Philypnodon macrostomus) has a big mouth. The second half of its scientific name – macrostomus – literally translates to large (macro) and mouth (stoma) in Greek.

Dwarf flathead gudgeon are not otherwise a large fish though – they’re commonly only 3.5 to 4 cm long but sometimes 5 cm.

They live in freshwater, like a majority of the Torrens is, or slightly salty, or brackish, water like where the river meets the sea at the Torrens Outlet.

There’s actually not a lot known about when this species breeds but it’s assumed to be similar to the larger variety, the flathead gudgeon – so, spring and summer.

Feral fish in the River Torrens / Karrawirrra Pari

Here’s 2 species that are found in the Torrens that are not our friends:

Goldfish. Photo from Canva
A goldfish. Photo: Canva.
1. Goldfish

Before you release your pet fish Bubbles, Calypso or Fishy into the wild, consider that the River Torrens / Karrawirra Pari is not actually the wild for these pets.

In fact, goldfish (Carassius auratus) were domesticated many moons ago in China from a species of carp – so yep, quite far away from our beloved Torrens.

Goldfish can grow to a fairly large size for fish – 40 cm – and we’re reading between the lines when the RSPCA says goldfish should only be kept with other fish, as long as ‘the other fish are larger than the size of the goldfish’s mouth’.

If you need to rehome your pet goldfish, we recommend contacting your local pet shop. We’d prefer they didn’t eat any of our native fish.

Controlling carp in the River Torrens / Karrawirra Pari. Photo: City of Adelaide.
Controlling carp in the River Torrens / Karrawirra Pari. Photo: City of Adelaide.
2. European carp

You’ve more than likely heard about the European carp (Cyprinus carpio) in the River Torrens / Karrawirra Pari. They’re also an introduced pest.

They’re a bottom-feeder and because of this, they muddy up the river, making it less suitable for other native fish.

We’ve been working on reducing them for years through an electrofishing technique, which involves stunning the fish and then removing the bad guys – like carp.

This method ensures that no other fish are harmed, but is super effective in carp removal, enabling more than 1000 to be collected over a 3-day period.

Once the carp are removed, they are disposed of in a humane way.

Carp removal is part of our Urban River Torrens Recovery Project.

Learn more about our native freshwater fish

Interesting in ID’ing some of our other local fish? Check out this chart for 13 local species and 7 introduced fish.

Main image: A flat-headed gudgeon. Photo courtesy of Jeremy Gramp.

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