From the UNIVERSITY OF BRITISH COLUMBIA and the fishy science department…
Fish are expected to shrink in size by 20 to 30 per cent if ocean temperatures continue to climb due to climate change.
A new study by researchers at the University of British Columbia provides a deeper explanation of why fish are expected to decline in size.
“Fish, as cold-blooded animals, cannot regulate their own body temperatures. When their waters get warmer, their metabolism accelerates and they need more oxygen to sustain their body functions,” said William Cheung, co-author of the study, associate professor at the Institute for the Ocean and Fisheries and director of science for the Nippon Foundation-UBC Nereus Program. “There is a point where the gills cannot supply enough oxygen for a larger body, so the fish just stops growing larger.”
Daniel Pauly, the study’s lead author and principal investigator of the Sea Around Us at the Institute for the Ocean and Fisheries, explains that as fish grow into adulthood their demand for oxygen increases because their body mass becomes larger. However, the surface area of the gills — where oxygen is obtained — does not grow at the same pace as the rest of the body. He calls this set of principles that explains why fish are expected to shrink “gill-oxygen limitation theory.”
For example, as a fish like cod increases its weight by 100 per cent, its gills only grow by 80 per cent or less. When understood in the context of climate change, this biological rule reinforces the prediction that fish will shrink and will be even smaller than thought in previous studies.
Warmer waters increase fish’s need for oxygen but climate change will result in less oxygen in the oceans. This means that gills have less oxygen to supply to a body that already grows faster than them. The researchers say this forces fish to stop growing at a smaller size to be able to fulfill their needs with the little oxygen available to them.
Some species may be more affected by this combination of factors. Tuna, which are fast moving and require more energy and oxygen, may shrink even more when temperatures increase.
Smaller fish will have an impact on fisheries production as well as the interaction between organisms in the ecosystems.
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Pauly and Cheung’s study “Sound physiological knowledge and principles in modeling shrinking fishes under climate change” was published in Global Change Biology doi: 10.1111/gcb.13831.
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‘“Fish, as cold-blooded animals, cannot regulate their own body temperatures. When their waters get warmer, their metabolism accelerates and they need more oxygen to sustain their body functions,” said William Cheung, …’
‘Tuna, which are fast moving and require more energy and oxygen, may shrink even more when temperatures increase.’
Um, some Tunas are actually warm blooded, and they are among the race horses of the sea. While it’s a much more primitive animal some Sharks are warm blooded as well; notably the Great White and the Bull sharks. Interestingly, Bull sharks, which range the oceans throughout the world, can swim upriver, one example being from the Gulf as far north up the Mississippi River as Dubuque, Iowa.
Me thinks Cheung and Pauly need to get out more. I’m guessing that the size of fish, just like most animals, tends to relate to the size of the area they inhabit, what they eat, and how much of it they eat.
Whoops. Bull sharks are not warm blooded. But, they can adapt for periods of time to freshwater and can swim upriver.
In addition to the Great White it’s the Mako shark that’s warm blooded. And, like the Tuna they’re speed demons as well.
The authors forget that the oceans are a three-dimensional universe with various thermohaline layers throughout the entire water column. If it’s too warm for a specific fish species at depth n then they’ll move lower to depth p where the oxygen level is higher and likely the richness of the food chain as well.
How, then, do they explain the great masses of paleolithic fish species that were many times larger than current fish species and existed in far warmer oceanic temperatures? Did they forget to include them into their analysis?
Yes, yes I believe they did.
/smh
The only thing that makes African Cichlids grow smaller is an enzyme in the water that inhibits growth. This allows more fish to occupy smaller water bodies.
Their size is not even remotely temperature dependent.
This study was done by “scientists” who don’t know anything about fish it seems
or O2 dependent, Cichlids thrive in low oxygen waters too. Growing in small pockets of water in African summers, you can bet the water is warm and the O2 low
Good point. Bettas like warm, still water.
I saw South American Killifish in tanks with only chlorophyllic oxygenation at 85F during my career as a university “building engineer”.
I would trust experienced aquarists over scientists on these matters any day. The corals debacle made that very clear to me
Aquarists suffer the consequences of bad science, scientists never do
Some of my projects when I was recording them. Not possible without precision, chemical and biological science.
https://youtu.be/UROlqJNLw6s
https://youtu.be/YA0lpPnm-_E
Recreation of Bolivian river Abuna water chemistry to breed wild caught Ancistrus Rio Abuna genus. Took me a year and a half to get these babies where most other ancistrus breed in toilet water 😀
8 weeks old
https://youtu.be/9jKbjKzq6gI
https://youtu.be/K7EOwnztInY
Dad, mom very shy.
https://youtu.be/HIDGNpP__LQ
Blackwater Amazon chemistry, and a taken in Bala shark, not really suited to this environment but he thrived nonetheless. Upsidedown catfish I had since fry size, had them for 4 years until I moved from Ireland to Finland. They start swimming upside down soon after birth and do so for the rest of their lives
https://youtu.be/cWWuaNIeNVs
Amazon, tetra mania. 120 fish in 180 liters, 2 filters, CO2 injection, pristine waters.
https://youtu.be/YYWcWlz25SE
I could post many more but spamfest 😀
William Cheung, co-author of the study, associate professor at the Institute for the Ocean and Fisheries and director of science for the Nippon Foundation-UBC Nereus Program. said “There is a point where the gills cannot supply enough oxygen for a larger body, so the fish just stops growing larger.”
Not sure where he gets that nonsensical idea from, in some 60 years of fishing i have always found that the larger the fish the larger the gills …… never heard of fishes gills stopping growing …. as the body size increases so do the gills.
The warmer the water, the bigger the fish, they need to look at the fish around warm water outlets from cooling towers and cooling systems which feed into rivers. That is always where the largest fish are.
” published in Global Change Biology ”
So a magazine dedicated to biological adaptation to climate change? Well THAT’S quite convenient for those who adhere to the AGW myth! An entire magazine dedicated to biological papers related to climate change!
IMO it’s a legitimate field of study which has become agenda driven because of its funding sources. Naturally climate does change and we should study the effects on flora and fauna as we ourselves adapt, mindful that the present lush greening of the planet is due to warming+CO2.
For example, as a fish like cod increases its weight by 100 per cent, its gills only grow by 80 per cent or less.
What if? The young fish has more gill than they need, and as they grow into adulthood, the gill size more closely matches what the fish need? Kinda like a puppy having huge feet, but they grow into them.
“Fish are expected to shrink in size by 20 to 30 percent if ocean temperatures continue to climb due to climate change.”
I need to see some proof that the atmosphere can warm the ocean, instead of the reverse being the obvious case. When the SSTs cycle to a 1970s like condition they will once again cry ice age.
There’s another common pressure towards smaller average fish sizes — overfishing. The more fishing pressure, the fewer fish reach the biggest possible size, across many species. Atlantic halibut used to reach several hundred pounds, but they are a slow-growing fish that was, in effect, mined. It’s the same dynamic as logging forests full of 600 year old trees, and letting them regrow for only 90 years.
Catching fish as soon as possible has a dysgenic tendency to eliminate the monsters, and work in favor of fish that mature early and lay eggs before they get caught.
That factor can’t be separated from other factors. The latest doomsday scenario about water temperatures is popular now, but if it’s disproven, pessimists will come up with something new.
‘Fish, as cold-blooded animals’
How scientific of them.
If the water is warmer, won’t they be warm-blooded animals?
Note that the poikilothermic generally don’t care what the temperature is. It is us homeotherms that care.
Stefan Reddish:I am not sure what you are questioning, but let me try to reply.For the same ocean surface energy balance I cited to Ian.W,consider a perturbation of 1 W/m^2 increase in the back radiation.The new balance shows an increase in surface temperature of 0.00227 K, and of the 1W/m^2 in back radiation,95.3% goes to reduce the convective heat loss from the near surface water,2.57% goes to increased evaporation,1.25% to increased emission, and 0.91% to sensible convection into the air.The ocean surface temperature plays a critical role in determining the various fluxes.Also, it is the very large convective heat transfer coefficient on the water side of the interface that dominates the response of the balance to perturbations.
The size-dependent estimate on weight is 24.9% per degree Celsius (assuming the fish in question don’t change their range as ocean temperatures change, which seems an unlikely assumption). This is the temperature of the *water*, not the sea surface. The heat capacity of the ocean is much, much larger than the atmosphere, it isn’t going to go up by 1C anytime soon.
Why does it seem like everyone constantly forgets that overall ocean temperature change is almost too small to measure since 1950?
If that’s a real question, rather than a rhetorical question, the answer might be: Anything that doesn’t conform to a doomsday scenario gets ignored. “Settled science,” and such. Everything is bad and getting worse. That’s my story and I’m sticking to it.
Here is the state of marine life in the UK from 1970-2013, when CO2 emissions went up dramatically:
Of all 104 Marine Species surveyed:
47% increased
28% little change
25% decreased
(62%-38% when little change excluded)
“Marine fish have been influenced by commercial fishing and climate change altering the composition of marine communities, the abundance of species and the body sizes of individual fish. Over our long-term period, the populations of a large proportion of smaller-bodied fish species have increased due to warming sea temperatures, while the populations of a smaller number of larger-bodied species have declined due to fishing” (emphasis added)
Source: State of Nature 2016 report (produced in partnership with 50 conservation organisations) – https://ww2.rspb.org.uk/our-work/conservation/projects/state-of-nature-reporting (Main Report p.45, plus Supplemental Data Tables, Table 1a).