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Farmed fish doing alright at CO2 levels twenty, fifty, seventy times higher than today

Posted By Jo Nova On November 30, 2016 @ 8:21 pm In Global Warming | Comments Disabled

The World Wildlife Fund tells us that global CO2 is bad for global fish stocks, but ponder that professional fish farms can reach levels of CO2 twenty or even seventy five times higher, and the fish appear to be doing OK. Current guidelines for fish farms even suggest that “safe limits of CO2 range from >5000 to >30 000 µatm*” which are “12.5 to 75 times higher than current atmospheric levels”.

So in another few thousand years we might really get into trouble with fish farms and climate change then? (Or maybe we won’t. James Hansen estimates if we burn every last barrel of fossil fuel on Earth we’ll get to 1,400ppm. The experience of fish farms all over the world is that fish can apparently adapt to levels ten times higher even than this worst case scenario.)

We have a situation where there are scores of reports fish suffering from ocean acidification and high CO2 levels, but they don’t mesh with the reality that fish farms have been dealing with for decades.  A new paper tries to figure out why this is so. The study doesn’t prove that there are no bad effects from higher CO2, but it puts the panic into a whole new perspective.

Current global CO2 levels are 400ppm, they’re projected to rise to 1,000ppm by 2100. Aquaculture only tells us about a certain kind of fish, but as far as dinner fish go, and the fear of humankind running out of fish and chips, I think it’s safe to say we have at least a thousand years to go before it’s a hot item. Chalk it up on the program for the 3016 Paris conference. Whatever.

Aquaculture, graphic, CO2 atmospheric levels, effect on marine life.

Aquaculture puts the panic into a whole new perspective.

The studies and the real world contradiction

Lots of academics have published papers that suggest that a mere doubling of CO2 will seriously muck up fish (to be technical) making them smaller, less viable, slowing their metabolic rate, etc etc. Recirculating Aquaculture Systems (RAS) are very intense. If you were inclined to worry about CO2 you might describe the loads of CO2 at RAS as “apocalyptic”. And this is not just RAS systems but aquaculture of all sorts:

“…elevated CO2 levels appear synonymous with intensive aquaculture more generally.”

“For example, over 40% of Norwegian salmon smolt hatcheries (flow-through and RAS) report CO2 levels >5400 latm (Noble et al., 2012), whereas Bangladeshi shrimp ponds are shown to experience CO2 levels averaging >17 000 latm (Saksena et al., 2006; Sahu et al., 2013).”

Here’s a big clue – Natural CO2 varies a lot — life adapts

In 2007, some oysters were hit with high CO2 levels and a pH as low as 7.6 and it did matter — but, but, but this was no man-made disaster — it was natural thanks to an upwelling of deep water with lots of CO2 in it.

In 2007, these impacts were realized with the upwelling of elevated CO2, aragonite undersaturated sea water off the US west coast,
significantly impacting oyster hatchery production as a direct result of changing climatic conditions  — Barton et al 2015, PDF paper.

The message is that the ocean has a lot of pH variation in it, and ocean life has probably been hit with high CO2 levels a lot of times since time began. I’ve been conversing with Patrick Moore, who’s done years of salmon farming himself and has been looking closely at the issue. There’s a lot more to come, but he and I agree that the most important message here is that life is adaptable. Within the gene pool are probably a lot of variations for coping with big changes, and a few generations of heavy selection transforms the population. We don’t need to wait for a big rare mutation. Life is probably tapping into a gene pool that has gone through major variations many times before.

Fish selected for aquaculture are obviously the kind of fish that do well in aquaculture. But there is a greater truth here and that is “multigenerational adaptation” which occurs in both fish farms and in the wild, but would be missed in short term studies.

“…strong and rapid evolutionary response. It is highly likely therefore that aquaculture practices operating at elevated CO2 concentrations would elicit sufficient selection pressure to directly select for CO2 tolerance during early life stages, leading to the rapid evolution of the population in just a few generations.”

 If CO2 levels are naturally all over the place it’s reasonable to assume that the genes for coping with it are naturally all over the place too. Fish managed to evolve from salt to fresh water in a mere fifty years, adapting to higher CO2 is probably easier. As Patrick Moore pointed out to me, the out — the implications of aquaculture species doing fine in much higher CO2 than could ever be prevalent as an average in the global ocean “are staggering”:

“The author surmises that species or varieties used in aquaculture may have become adapted to CO2 at 5,000 ppm or higher within a few generations. If so there is no plausible reason why this could not also take place in nature. It appears as though marine and freshwater species have about the same tolerance for atmospheric CO2 as air breathing animals do, i.e. >20,000 ppm (which translates to about 25ppm in the water)

  —   Patrick Moore is “The sensible environmentalist”

For more info on the details of the effect of high CO2 levels on humans read this link.  (h/t Tomomason for that link.)

Aquaculture is not the global ocean — obviously

There are other obvious reasons why studies on wild fish or lab fish are different to farmed fish:

“…animals reared in many aquaculture settings are living in a relatively benign environment, being provided with abundant food, relatively constant environmental conditions, protection against disease and absence of a predation threat.

And fish farm managers are not doing pscyh surveys looking for reckless fish either.

Can’t think why the media haven’t interviewed some fish farmers…

Obviously fish farms are not the same as the whole ocean ecosystem — we might be picking fish that like CO2 or having bred them to be happy in it, and these farmed fish don’t have predators. Still, if fish farms had found their yields suffered at 400ppm rather than 4,000 or 40,000, perhaps the media might have mentioned it?

What this means and does not mean

So finfish seem to adapt pretty well to crazy levels of CO2. Shell fish are a more complicated, and I’ll go in to more detail another time. This study does not mean that adding CO2 has no effect, and that there won’t be some winners and losers.  Just because a fish can make a happy meal does not mean  it was a happy fish. But the scale of the fear mongering on ocean acidification needs a big reality check, and if the public knew that CO2 levels were  a magnitude higher in working fish farms they might not need therapy and trigger spaces to cope with the nightly news.

With CO2, 400 is max,
In p.p.m. for most climate quacks,
But, when fish stay alive,
At 8,000 and thrive,
Then, what warmists hold true aren’t facts.



Lessons from two high CO2 worlds – future oceans and intensive aquaculture
Robert Ellis, Mauricio Urbina and Rod Wilson.


Exponentially rising CO2 (currently ~400 latm) is driving climate change and causing acidification of both marine and freshwater environments. Physiologists have long known that CO2 directly affects acid–base and ion regulation, respiratory function and aerobic performance in aquatic animals. More recently, many studies have demonstrated that elevated CO2 projected for end of this century (e.g. 800–1000 latm) can also impact physiology, and have substantial effects on behaviours linked to sensory stimuli (smell, hearing and vision) both having negative implications for fitness and survival. In contrast, the aquaculture industry was farming  aquatic animals at CO2 levels that far exceed end-of-century climate change projections (sometimes >10 000 latm) long before the term ‘ocean acidification’ was coined, with limited detrimental effects reported. It is therefore vital to understand the reasons behind this apparent discrepancy. Potential explanations include 1) the use of ‘control’ CO2 levels in aquaculture studies that go beyond 2100 projections in an ocean acidification context; 2) the relatively benign environment in aquaculture (abundant food, disease protection, absence of predators) compared to the wild; 3) aquaculture species having been chosen due to their natural tolerance to the intensive conditions, including CO2 levels; or 4) the breeding of species within
intensive aquaculture having further selected traits that confer tolerance to elevated CO2. We highlight this issue and outline the insights that climate change and aquaculture science can offer for both marine and freshwater settings. Integrating these two fields will stimulate discussion on the direction of future cross-disciplinary research. In doing so, this article aimed to optimize future research efforts and elucidate effective mitigation strategies for managing the negative impacts of elevated CO2 on future aquatic ecosystems and the sustainability of fish and shellfish aquaculture.

* µatm is very similar to ppm. pCO2 = xCO2 * ( p(air) – p(H2O). So  360ppm is “typically” eq to 350 µatm or something like that, in case you were wondering.


Robert Ellis, Mauricio Urbina and Rod Wilson (2016) Lessons from two high CO2 worlds, Global Change Biology. doi: 10.1111/gcb.13515

Barton A, Hales B, Waldbusser GG, Langdon C, Feely RA (2012) The Pacific oyster, Crassostrea gigas, shows negative correlation to naturally elevated carbon dioxide levels: implications for near-term ocean acidification effects. Limnology and Oceanography, 57, 698–710.

h/t Willie S

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