Freshwater, Sustainability, Trout

The impact of trout on threatened galaxias

Spotted galaxias or mountain trout (Galaxias truttacea). Photo by Nathan Litjens of All rights reserved.
Spotted galaxias or mountain trout (Galaxias truttacea). Photo by Nathan Litjens of All rights reserved.

The issue of trout impacts on native fish raises its head from time to time in the recreational fishing community. The latest flare up happened a bit over a month ago when the Threatened species commissioner Gregory Andrews posted this facebook post.

Introduced ‪#‎trout‬ are great fun to catch, but did you know they are having a devastating impact on native fish like these precious little galaxias? There are 27 species of galaxias in Australia and eight are on our national‪#‎threatenedspecies‬ list. One species, the Kosciuszko galaxias, can be found in waterways almost on the summit of Mount Kosciuszko, including in the well known Blue Lake! They live in some of our most remote and tiny mountain streams, but many of these streams are being occupied by introduced brown and rainbow trout that are eating our galaxias out of existence.

Brown and rainbow trout were introduced into Australia in the late 1800s and are the basis of some valuable recreational fisheries. However, this role needs to be balanced with the serious environmental impacts they have. Our streams and rivers are uniquely and naturally stocked with diverse Australian species, and while Australians love fishing for the North American rainbow trout and the English brown trout – native fish such as Macquarie perch and galaxias belong in our waterways and give our Australian streams their unique character.

Trout are pushing galaxias to the extreme upper reaches of streams, leaving them vulnerable to bushfire and stream drying in droughts. An example of this devastating combination occurred in 2009, when the Black Saturday Bushfires incinerated the forests and bush surrounding barred galaxias catchments. Ecologists took fast action and saved these populations from ash poisoning, keeping them alive in special aquariums for several years until their streams were safe to return to.

Despite the known impacts of introduced trout on native species, illegal stocking of trout in Australian waterways is still occurring. The ultimate goal is to improve galaxias conservation outcomes while still maintaining legal recreational trout fisheries. Improving habitat is also crucial to maintaining healthy galaxias populations and the Australian Government is investing over $265,000 through the 20 Million Trees and National Landcare Programmes to benefit galaxias species, and providing 10 Green Army Gov teams for on-ground action.

A heated debate ensued on facebook (check out the comments). To be honest, I find it hard to believe people are still denying that trout can have a negative impact on some native fish. The truth is, the impact trout have on many galaxias species is well studied in Australia and New Zealand and should not be at all controversial. That work shows that for many species, trout are a clear and present threat and one of the major drivers of declines in abundance. For example, for species such as the Shaws galaxias, Dargo galaxias, Tapered galaxias, Swan galaxias, Stocky galaxias and Barred galaxias trout are the major threat and one of the major reasons those species are now threatened. Most of those species have completely disappeared from streams that contain trout and now only hold on in a few remaining pockets of trout free habitat in the extreme upper reaches of catchments. In other galaxias species the presence of trout is associated with declines in abundance and changes in feeding behaviour. It is true that some species of galaxias can co-exsit with trout (e.g. some of the trout streams I fish have healthy populations of Ornate galaxias (Galaxias ornatus), which at least in some circumstances appear to deal with the impacts of trout quite well), but that is definitely not true for all of them. What is clear is that the idea that trout don’t have an impact on at least some species of galaxias is an out and out myth. It simply isn’t true. For the species most affected removing trout from some sections of stream may be the only way to rebuild populations and ensure the continued existence.

As recreational anglers, its high time we accepted that trout can have an affect on many species of galaxias and that if we want those galaxias species to have a secure future, at some point we will likely need to provide them with more trout free habitat (e.g. projects like this and this). While that may seem like a threat, in truth, as recreational anglers we have little to fear. Most threatened galaxias species do not live in high quality trout fisheries, but rather way up in headwaters rarely fish by anglers. Added to this, trout removal and building barriers to prevent re-colonisation is expensive and generally only possible in a small percentage of any catchment. That is, any future works to provide trout free safe havens for threatened galaxias species is likely to affect a miniscule percentage of fishable water and have almost no impact on recreational anglers.

Thats not to say conflicts wont arise or that the impacts of trout on native fish are as clear cut in other regions or in other species. In those cases, the questions we should be asking aren’t do trout have an impact (they will have an impact), but rather what is the impact they have and how and where can it be lessened in an equitable way? How can fisheries be managed in ways that limit trout impacts in some areas while maintaining the social and recreational values of our rivers? How can we secure the future of threatened species, while also maintaining or improving fishing opportunities where possible? How can we best balance the needs of conservation with the needs of recreational fishers (taking into account the social and economic benefits of recreation fisheries) to achieve fair outcomes for both groups?  Those are the vigorous debates we should be having, not continually banging on about whether trout are absolute angels or absolute villains. That debate has been done to death, its boring and it achieves nothing. Its time we moved on.

I look forward to all your views about how we might answer those questions.



Note: Thanks to Nathan Litjens of for allowing us to use his amazing photo. Check out more of his work at flickr, he really takes some amazing photos!


Note: In response to people raising these impacts you will often hear arguments like “trout have been here for 150 years, the galaxias are still here, trout can’t be that bad”. This clearly isn’t true for species that now only exist in trout free habitat, species that are clearly impacted by trout. Similarly, its common to hear statements like “you aren’t factoring in the impacts of carp, gambusia and redfin or habitat degradation, its not just trout”. However, in many of the headwater streams inhabited by threatened galaxias, habitat is often pristine and carp, gambusia and redfin don’t exist. They clearly aren’t major drivers of declines. There is no doubting that in other environments all these factors have played a large part in the decline of native fish. They are very important issues in so many of our rivers, just not the major ones in many of the areas where trout have impacted on various galaxias species.


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