Conserve & Manage Australian Trout and climate change

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  • #860362

    bribri
    Participant

    As we enter yet another significant heatwave in Southeast Australia, I can’t help but ponder what the future of Australian trout fishing looks like.

    Anecdotally, my local stretch of river has undergone a substantial shift from a trout-dominated fishery to a native-dominated fishery over the last 10-15 years or so, to the point that trout are no longer a viable target. This is in the absence of any major bushfires or changes to stocking regimes. Without having data to back it up, you’d strongly suspect that rising water temps and reduced flows are the main factors. This is not an isolated trend – finding trout in many rivers often seems to require heading further upstream than you’d need to historically.

    No doubt, trout will hang on at high altitudes and in tailraces well into the future, but IMO many sub-alpine streams are likely to be increasingly unreliable as trout fisheries. I can’t see how existing practical solutions (e.g., planting trees to increase shading, adding snags, etc) can be applied on a scale sufficient to make any meaningful difference.

    I’m not a doomsdayer by any stretch, but does anyone else feel a sense of inevitability that many of our Australian trout fisheries are essentially on borrowed time?

    #860375

    flylife
    Moderator

    I share your pain, and have been wrestling with an article in collaboration with some heavyweight academics in the fly fishing world. This year in Tas is shaping as being drier and hotter than 2008/2009 when I wrote Watershed.

    #860394

    chf
    Participant

    I think we can all see it , though I hope trout shall hang on in a fair number of waters .

    Please write the article flylife .

     

     

    #860395

    woody-wood
    Participant

    You think the Kiwi’s are complaining now, just wait til the only viable trout fishery in Australasia is NZ and there a four times the numbers of anglers compared to now.

    #860399

    mitch aka 2 fish
    Participant

    australian trout will adapt… but they’ll need selective breeding to do so.

    and here lies the conundrum… propagating, other than a ‘put and take’, will be your future.

    you read it here first folks…

     

     

    cheers,

    shawn

     

     

    #860412

    flylife
    Moderator

    The article in prep isn’t trout or climate change specific but more about the broader trends and changes afoot in fresh and salt water across Aus and NZ.

    Anyone watched the ‘Years and Years’ series on SBS?🧟‍♂️

    #860426

    Fish4Sport
    Participant

    Hi

    Regarding the question “does anyone else feel a sense of inevitability that MANY (emphasis added) of our Australian trout fisheries are essentially on borrowed time?” I think that the logical answer is yes.

    However, the causes and consequences of climate change are debatable and uncertain (and can be very emotional, with rude, nasty comments – luckily the comments on this site are usually polite and courteous ).  Therefore, it seems likely that some areas will be adversely affected and some areas might be positively affected.  For example, warmer temperatures in the Tasmanian highlands might result in a more productive trout fishery.  Plus, some scientists predict higher rainfall with global warming – in some areas.  Perhaps Tasmania? I doubt that anyone knows with 100% certainty.

    I think that it is just a matter of the extent of change.  For example, in Tasmania it was global warming that created the foundations for a trout fishery when, starting from approximately 15,000 year BP, global warming slowly melted the ice caps, leaving huge numbers of tarns and glacial lakes, plus terrain for Hydro – ideal for trout (it also created Bas Strait, which some of my mates think is good as it results in less trout fishermen from the mainland – I do not share this adverse view on visiting anglers, most of whom catch and release )

    Regards

    Fish4Sport

     

     

    #860428

    flylife
    Moderator

    There is a scientific paper out there with long term predictions of Tasmania’s shallow lakes becoming less suitable for trout, even in the highlands. But that is a long way off. ‘Drought proofing’ our lowland farms will also be at the cost of trout.

    #860434

    orangefly80
    Participant

    This is definitely a concern for the trout streams in my area (sub-alpine, Central Tablelands NSW).

    Since the late 1990’s (aka the halcyon days) the streams have slowly lost their flow due to the drought, urbanization and industry which has allowed invasive species to choke the water way. The terrible (but understandable) method of willow eradication has created barren lifeless stretches of creek/river which slowly warm during the summer period.

    Of biggest concern certainly in my area is the arrival and almost immediate takeover of European Carp. They presumably were holding back downstream in the warmer waters below the trout streams but as it has degraded they simply move in and rule the roost. these days its nothing to go looking for trout and only find carp in once high quality trout streams.

    Whilst i do have my “secret” spots that still hold trout i have noticed a increasing trend of less fish and poorer quality fish. I am also not a dooms dayer but i agree, certainly for my area, that these fish are definitely on borrowed time

    #860475

    Boris
    Participant

    If I may,

    Climate change is a political move emanating from the global oligarchs who want to institute another feudal system albeit with smart cities and the internet of everything.  They know they can’t force us – the west – but they can utilise propaganda and lies like they have used before. They largely control the media so the propaganda is relentless. It’s more of the Lima Declaration …

    However, the recent graphic slides shown by the BOM and trumpeted by the media give the impression that these temperatures have never been see before in Australia. The trouble with the graphic figure is omitted data prior to 1910 which gives the impression that temperatures are hotter now than ever before. If they included the data prior to 1910 it would be clear these temps have been recorded before. So the upshot is people are fearful as they succumb to the relentless misrepresentation.

     

    I wouldn’t give up on trout, yet – but carp eradication needs to be done.

     

     

     

    #860507

    MJL
    Participant

    Hi

    BOM report data from 1910 as the beginning of their own network of standardised stations. No data is “omitted”.

    Others have compiled longer historical data sets (see below from Berkeley Earth) and considered objectively, temps prior to 1910 were not warmer that today.

    http://berkeleyearth.lbl.gov/auto/Regional/TAVG/Figures/australia-TAVG-Trend.pdf

    #860513

    Boris
    Participant

    See the corroboration of the higher temp record in newspaper clippings at the time.

    Berkeley Earth squares the newspaper clippings that corroborate the higher temps how?

    By just ignoring them! 😆

    #860519

    MJL
    Participant

    The clippings suggest it was hot but not that it was hotter than today. A record is expected today breaking other records set earlier this week.  Data from before 1910 included.

    Berkeley Earth is science.  Tony Heller videos on YouTube are not.

     

     

    #860520

    DrGraham
    Participant

    I have studied the ecology of marine systems for over 40 years, starting in tropical Queensland, then east coast Tasmania, and the last 36 years has focussed on studying and monitoring the impacts of climate change on the Antarctic marine ecosystem, notably plankton and Antarctic krill. Fly-fishing has been my passion for much the same period and of course I have taken more than considerable interest in the potential climate change effects on trout and our freshwater systems as a whole. When I read comments that climate change is some sort of hoax, I am not just frustrated but deeply, deeply offended by such ignorance.

    There are numerous stressors that can affect the survival of trout:

    1) Rising temperature. Trout, like all organisms have temperature limits. The world has been in a warming phase since 1977, that’s 42 years and it’s still going up. Temperatures in Australia continue to rise. On Tuesday this week, 17 December, the mean temperature for all of Australia was 40.9 C which broke the previous record of 40.3 C. Meteorologists predicted that record wouldn’t last long. It barely lasted two days with yesterday setting a new record 41.9 C. We haven’t reached the peak of summer yet.

    2) Reduced rainfall. The country has been in the grip of droughts for some time, and have been extending geographically and temporally (especially duration). Areas noted previously for good rains and pastures are suffering. South-east Tasmania had slightly above rainfall in August but the rest of winter, and all of spring since have experienced rainfall well below average and it would appear that it is starting to become the norm. The long-term prognosis is that regions that are already dry will become drier.

    3) Growing demand for what water we have – for domestic, commercial, agricultural use etc. Melbourne is growing faster than Sydney. Both cities are concerned about having enough water for future use. Adelaide in the meantime virtually lives on bottled water because water from the Murray is effectively undrinkable without extensive treatment. Demands on water from upstream of the Murray system will only increase.

    4) Siltation/stagnation of our waterways. Land degradation from loss of vegetation (caused by multiple factors) can lead to erosion of top soil and river banks. There’s the additional issue of probable eutrophication.

    5) Introduced species. We’ve seen the effects of carp and allied species in Australia and Didymo in New Zealand.

    What does this mean for trout, can they adapt? Short term changes in temperature, rainfall, waterfall etc are part of the seasonal cycle and trout already cope with that. They have the behavioural skills to seek better conditions, albeit temporarily – deeper water in rivers or lakes. The longer-term is the issue. Initially I expect the distribution to contract to higher cooler altitudes, providing there’s water, but the changes we are seeing now are occurring faster that will allow physiological or evolutionary adaptation. Could we engage in selective breeding? Possibly, but what’s the cost and who is going to pay? Hybrid trout may be more robust but of course they can’t breed. Any one of the stressors I listed could have an effect, but they don’t act in isolation. The potential is for a small change in temperature, together with reduced water flow, reduction in water quality to have a combined, multiplying effect that could be more harmful than a large change in just one stressor. So far my focus has been on the summer months, but what happens in late autumn and early spring if there is no water in the spawning runs for browns and rainbows? We are already seeing poor rainfall in winter months.

    The biggest threat I see for our freshwater systems is the complete lack of an effective and coherent water policy in Australia. States bicker between themselves, overseen by a Federal government that at best doesn’t take climate change seriously (most of the Libs) or completely deny it (most of the Nats). Instead, all parties would rather blame others than recognise their own legislative and scientific impotence.

    As a scientist, would I stand up in a court of law and give a 100% complete assurance that climate is real and the consequences deleterious? No, but I’ll give you 99%. I would really like to hope that there is a small chance we are wrong, but the weight of evidence is overwhelming. The question I pose to climate change deniers, can you give me a 100% complete assurance that deleterious climate change is not real? Are you prepared to bet the future of your children and grandchildren that everything is perfectly fine? Because, that is what you are doing.

    #860521

    Boris
    Participant

    The clippings suggest it was hot but not that it was hotter than today. A record is expected today breaking other records set earlier this week. Data from before 1910 included.

    Berkeley Earth is science. Tony Heller videos on YouTube are not.

    Wrong!  Hotter -Mildura 1906 – 124’F or 52’C look at the photo and read the temps in the clippings – lots more at very high temps such as Adelaide 127’F etc etc

    ‘authority’ – the weakest argument 😆

     

     

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