The Plight of a Mysterious, Rare Blue Mountains Fish   

blue mountains perch

A mature Blue Mountains Perch. (Photo: NSW Fisheries)

Story by Julie Nance

The Blue Mountains Perch may not be as adorable as a cuddly koala, but it is also an endangered animal in need of awareness and support. Populations of the freshwater fish have been hit hard by drought, fire and flooding over the past few years. A NSW fisheries study, while sobering reading, is helping experts develop a plan to save the fish.

Key Points:

  • The Blue Mountains Perch has dwindled in numbers and become extinct in parts of Greater Sydney, but populations are hanging on in the Blue Mountains.
  • We can all play a part in protecting the fish by reducing erosion on our properties and highlighting to others that it exists and it needs our help.  

A couple sits on a large rock enjoying a romantic picnic beside a beautiful Blue Mountains waterhole. Little do they know they are in the presence of an ancient and beautiful animal.

The Blue Mountains Perch lies camouflaged at the bottom of creeks and deep water holes during the day. In the night-time it is active; its big eyes seeking out water bugs and smaller fish to feast on.

While a successful predator, the Blue Mountains Perch has been at the mercy of environmental forces that have treated it very harshly.

According to a NSW Fisheries study, Blue Mountains Perch populations were under immense stress from a prolonged drought from 2017 to 2019. Approximately half of their habitat was severely impacted by the 2019/20 “Black Summer” bushfires that followed.

In February 2020 heavy rains throughout the Hawkesbury-Nepean catchment caused severe runoff and hillslope erosion. Large volumes of sediment were deposited in waterways, threatening aquatic species with ongoing habitat loss. It is thought the Blue Mountains Perch was further impacted by these rainfall events.

The study, ‘Drought, fire, and flood: A population assessment of the Blue Mountains perch (eastern Macquarie perch) ….’ charts the findings of a comprehensive assessment of the distribution of Blue Mountains Perch, mainly between 2021 and 2022. A total of 88 sites were targeted within the Hawkesbury-Nepean and Hunter catchments.

The surveys involved the use of electrofishing: passing an electrical current through water, which temporarily stuns fish so they can be caught, processed and released. Netting was also used as well as environmental DNA (eDNA) analysis. This new technology finds traces of DNA in the water as a way of knowing if a species is present, without catching or disturbing it. In total, 27 Blue Mountains Perch were captured, ranging in length from a 30 mm juvenile to a 235 mm sexually mature fish.  

electrofishing for blue mountains perch

NSW Fisheries experts electrofishing for Blue Mountains Perch. (Photo: NSW Fisheries)

Blue Mountains Perch were absent from seven of the 20 water bodies that the species was known to occur in prior to the 2017 to 2019 drought, 2019/20 bushfires and 2020 flooding. This represents the potential loss of Blue Mountains Perch from approximately 35 per cent of sampled water bodies known to previously contain the fish.

One of the Perch’s biggest advocates is Will Goodwin, a member of Blue Mountains City Council’s Healthy Waterways team.

“They are a really pretty fish; they’ve got this beautiful, mottled brown and silvery grey on the side and they live in such beautiful habitat,” he says.

“We literally have an animal named after the Blue Mountains that pretty much none of us have heard of.  Many of us have come far closer than we realise at Blue Mountains swimming holes.

“We have the power to really stand up for it. We could be looking at an extinction here, but if the right things are done, we can see the Perch completely bounce back and it can be a huge success story. The biggest thing the Blue Mountains Perch needs is advocacy.”

juvenile blue mountains perch

A juvenile Blue Mountains Perch. (Photo: NSW Fisheries)

Will says the Perch study is helping Blue Mountains City Council better prioritise its conservation work, including improving waterway health. He says a Council Biodiversity Strategy will soon be on public exhibition.

“Based on the map/site coordinates in the study, I’ve been able to determine which sites fall in our LGA and I’m really happy to see that a number of them returned positive results for Blue Mountains Perch,” Will says. “Populations are hanging on in the Blue Mountains, but they need help.”

will goodwin bmcc

Healthy Waterways team member Will Goodwin, who is passionate about freshwater fish (and turtles). (Photo supplied)

The report says there are new threats to the Blue Mountains Perch. This includes alien species invading their habitat e.g. Redfin perch; diseases such as Epizootic Haematopoietic Necrosis Virus (EHNV); and potential habitat loss from possible raising of Warragamba Dam and mining within the Nepean River sub-catchment.

Long-term monitoring (5+ years) of the Blue Mountains Perch has been recommended in the report, as well as key habitat remediation activities including desilting, riparian improvements, bank stabilisation, and the restoration and conservation of in-stream rocky habitat. 

 blue mountains perch habitat

Habitat where the Blue Mountains Perch is believed to occur. (Photo supplied)

healthy creek

Will: “This is a fairly healthy creek in a Blue Mountains Perch catchment. I took this underwater photo at night, using a flash.” (Photo: Will Goodwin)

The report recommends: “Urgent management actions are required to protect Blue Mountains Perch from further decline and improve the species’ resilience.” 

Will says a lot of conservation activities already carried out in the Blue Mountains has indirectly benefited the species, including protecting and restoring creeks.

“In a happy accident, our existing stormwater works such as the Glenbrook raingardens project are our biggest tool in our tool belt to help the Blue Mountains Perch,” Will says. “Moving forward, we’re looking at prioritising Blue Mountains Perch catchments for future raingarden projects and funding.”

The Blue Mountains Perch was long thought of as a variation of the Macquarie Perch, a freshwater fish native to cooler, mid-altitude areas of south-eastern Australia. However, past studies, both genetic and morphological (looking at the form and structure of an organism or any of its parts), are providing strong support for it to be classified as a separate species.

“That’s part of the problem and part of the mystery of the fish – it used to be considered Macquarie Perch. Because it doesn’t officially scientifically exist as its own species, it is difficult to protect it.” – Will Goodwin

When you listen to Will enthusiastically talk about the Blue Mountains Perch, you can see why he has such a strong desire to help it. He highlights their “clever strategy” to keep their eggs safe, laying them at the top of a fast-flowing stream.  

“As the eggs bounce along in the current, they get wedged amongst the rocks and pebbles,” Will says. “The rocks keep predators out, and the constant flow of water keeps them clean and well oxygenated.”

Will says unfortunately there is now far too much sediment in our streams.

“It comes from our backyards and construction sites, but also from the erosion of creeks as they get blasted with urban stormwater,” he says.

“Even the fast-flowing sections of streams get covered with this blanket of sand on the bottom. Without that rocky habitat, there’s no way for this fish to breed”.

sediment on creek bed

Known Blue Mountains Perch habitat that has been blanketed by sediment. It’s a fast-flowing riffle, so it should naturally have a nice rocky bottom. All the little cracks have been filled in. (Photo: Will Goodwin)

So how can we help?

Will says individuals shouldn’t feel powerless to assist the Perch. He cites advocacy for koalas and the Regent Honeyeater as examples of people power making a positive difference.

“It’s about recognising the beauty of this fish and getting people behind it,” Will says.

“No one is going to protect something they haven’t even heard of, and the Blue Mountains Perch has missed out on much needed protection because of that. Just by spreading the word, you can make a huge difference for this fish.”

Take Action:

  • Try to reduce erosion: look out for any bare earth on your property, and keep it covered with plants or mulch.
  • Tell someone: the more people that know about this species, the more protection it will get. Sharing this story, or just mentioning it to a friend or family member is one of the best things you can do for it.
  • Read about a stormwater treatment initiative at Glenbrook featuring the type of raingarden that is ultimately helping the Blue Mountains Perch: It Takes a Village to Care for a Creek.

Share this article:

This story has been produced as part of a Bioregional Collaboration for Planetary Health and is supported by the Disaster Risk Reduction Fund (DRRF). The DRRF is jointly funded by the Australian and New South Wales governments.

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About Julie Nance

Julie Nance is a community storyteller with the Blue Mountains Planetary Health Initiative. In her coverage of the Lower Mountains area, she brings 30 years’ experience in communications, publishing and journalism. After specialising in health and social issues as a journalist, Julie led creative teams in the government and not-for-profit sectors including the Aged Care Quality and Safety Commission, YMCA NSW, Cancer Council NSW and The Children’s Hospital at Westmead. Julie is passionate about empowering people with quality information to help them make informed choices.

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