Ocean warming could lead to smaller fish size, study finds

Sep 30, 2012
ocean

Changes in ocean and climate systems could lead to smaller fish, according to a new study led by fisheries scientists at the University of British Columbia.

The study, published today in the journal Nature Climate Change, provides the first-ever global projection of the potential reduction in the maximum size of fish in a warmer and less-oxygenated ocean.

The researchers used computer modeling to study more than 600 species of fish from oceans around the world and found that the maximum body weight they can reach could decline by 14-20 per cent between years 2000 and 2050, with the tropics being one of the most impacted regions.

"We were surprised to see such a large decrease in fish size," says the study's lead author William Cheung, an assistant professor at the UBC Fisheries Centre. " are generally known to respond to climate change through changing distribution and . But the unexpectedly big effect that climate change could have on body size suggests that we may be missing a big piece of the puzzle of understanding climate change effects in the ocean."

This is the first global-scale application of the idea that fish growth is limited by , which was pioneered more than 30 years ago by Daniel Pauly, principal investigator with UBC's Sea Around Us Project and the study's co-author.

"It's a constant challenge for fish to get enough oxygen from water to grow, and the situation gets worse as fish get bigger," explains Pauly. "A warmer and less-oxygenated ocean, as predicted under climate change, would make it more difficult for bigger fish to get enough oxygen, which means they will stop growing sooner."

This study highlights the need to curb and develop strategies to monitor and adapt to changes that we are already seeing, or we risk disruption of fisheries, and the way work.

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More information: DOI: 10.1038/nclimate1691

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Kron
1.8 / 5 (12) Sep 30, 2012
This is backwards. As oxygen content decreases per given volume due to heat increase, organisms adapt by increasing intake potential. In other words, creatures grow in size increasing their lung surface in order to capitalize on the lower atomic content per volume of space. Hotter temperatures cause a size increase as an adaptive evolutionary response, and not the other way around.

Analysis of time periods supports the claim that warming causes size increase, while cooling causes size decrease.
kochevnik
3.4 / 5 (5) Sep 30, 2012
Hotter fish don't live as long, and don't attain full size
Kron
2.4 / 5 (12) Sep 30, 2012
The problem with computer modelling is that the results are variable dependent, and the variables are human dependent. Computers aren't prone to error...but humans are.
Kron
1 / 5 (6) Sep 30, 2012
Hotter fish don't live as long,

This is true. The hotter the star the faster it burns.
and don't attain full size

This is theoretical, dependent on subjective inferrence. A shorter lifespan means shorter lifecycle. I would reason that the increase in temperature equates to faster maturation, the fish reaches full size sooner.
Sean_W
2.6 / 5 (15) Sep 30, 2012
Computer models prove that fish will be smaller. Genius.

"We were surprised to see such a large decrease in fish size,"


No, they were not surprised. They programmed it into the model in the assumptions they made. How is this garbage never ever criticized by people who believe the warmest doctrine? Lots of time I see people making bad arguments for positions that I support and I never say to myself that I should backup the asinine just because they are "on my team". Can followers of the warmists never see the smallest flaw in their leaders work? Do they believe that nothing a climatologist comes out with could ever be wrong?
JoeBlue
1.8 / 5 (10) Sep 30, 2012
@Sean- It's pseudo-science. You don't have to be correct to garner support. You just have make headlines and find someone to back you financially to continue making headlines.
VendicarD
3.9 / 5 (7) Sep 30, 2012
Lung volume will grow at less than **3, but body mass will grow at **3.

Hence nature prefers smaller organisms in oxygen deprived environments. All else being equal.
Urgelt
2.9 / 5 (8) Sep 30, 2012
I guess the denialists are on holiday today. Not much here.

Too bad. If there's anything funnier than Jon Stewart mocking denialists and right-wing ideologues, it's denialists and right-wing ideologues themselves pretending to know stuff and failing miserably.
Benthos
4.5 / 5 (4) Oct 01, 2012
It all comes down to surface area to volume ratio's (sa:vol). The bigger an organism is the lower it's sa:vol that is why you will find larger representatives of species in cooler climes as larger animals can regulate temperature better as they have less surface exposed per unit mass.

The same goes with lungs and gills - smaller animals/organs have higher sa:vol there fore smaller animals have more oxygen collecting surface available per unit mass. The other alternative is to to grow much larger lungs or gills to maintain the mass. However nature works on efficiency and advantage and it is much easier to limit your growth size than alter your internal organ distribution and dimensions. especially with limited time at your disposal.
JRi
5 / 5 (4) Oct 01, 2012
Well, at least this won't directly affect whales and dolphins since they are not fish and breath air. Of course they may have difficulty to find enough food then.
ubavontuba
1.4 / 5 (11) Oct 01, 2012
I can't believe anyone buys into this. Anyone familiar with ocean habitats knows the largest fish species are found in warm and temperate waters. Marlins, for example, actually seek out warm water.

http://animals.na...-marlin/

Size is more about feeding efficiency, and fish generally feed better when their metabolism is higher (warmer).

And actual empirical studies show fish grow larger in warmer vs. colder water:

http://www.pvj.co...-108.pdf

Here they show fish grew fastest in warm water as juveniles, but grew faster in slightly cooler water as their mass increased.

http://www.ncbi.n...2798058/

When climatologists stop relying on computer models, and rather use empirical data, maybe then they might have something to write about.

kochevnik
2.7 / 5 (9) Oct 01, 2012
You obviously never had an aquarium, ubavontuba. Your own words contradict you. You stated that the large size is gained in colder waters. Of course a warm sea fish can be larger. The point is that it's cold water relative can be larger and live longer. Of course many fish only live in temperate waters, so a control is lacking for study.
VendicarD
3 / 5 (6) Oct 01, 2012
UbVonTard confuses the effect of temperature on growth rates of existing organisms with the effect of temperature on the evolution of the size of those organisms.

"And actual empirical studies show fish grow larger in warmer vs. colder water:" - UbVonTard

Once again, his display of ignorance is legion.
ubavontuba
2.1 / 5 (7) Oct 01, 2012
You obviously never had an aquarium, ubavontuba.
I grew up around aqauriums, and the sea.

Your own words contradict you. You stated that the large size is gained in colder waters.
"Slightly cooler" is not the same thing as "cold."

Did you honstly misunderstand, or are you intentionally trying to twist the argument?

Of course a warm sea fish can be larger.
That's not what the article is stating.

The point is that it's cold water relative can be larger and live longer.
Or not. The studies I provided state the fish grew poorly in cold water.

Of course many fish only live in temperate waters, so a control is lacking for study.
All you've said here is this study is garbage.
ubavontuba
2.1 / 5 (7) Oct 01, 2012
UbVonTard confuses the effect of temperature on growth rates of existing organisms with the effect of temperature on the evolution of the size of those organisms.

"And actual empirical studies show fish grow larger in warmer vs. colder water:" - Uba
Vendibot is retarded. He doesn't understand that stating, "the largest fish species are found in warm and temperate waters." means fish naturally evolved to be larger in warm water.

Dug
4.3 / 5 (4) Oct 01, 2012
The presence of Manta rays, whale sharks, mola mola, the goliath grouper and many other trop."giant" species could argue that the comp.mod. designers should have taken a few basic marine biology courses. While lower saturation levels in tropical waters appear to be the governing factor, they aren't necessarily so - regarding oxygen availability. Algae in the photic zone during day hours supersaturate the waters around them by secreting pure oxygen which is more soluble than the oxygen at the air interface - so O2 levels can be higher than saturation temps. Something tropical aquaculturist deal with daily. Another argument against the study's conclusions is that there is much greater speciation in the tropics than in temperate and cooler waters, a quantitative indication that warmer waters produce far greater adaptability mechanisms - including to low O2. This is a case wherein the program's inadequate variables were modeled - unsuccessfully, but projections were made anyway.

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