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Graham Raby
@graham-raby.bsky.social
48 followers 63 following 10 posts
Associate Professor at Trent University (Canada).

www.rabylab.com
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graham-raby.bsky.social
In this new study, we provide new data relevant to the debate about whether oxygen limitation is a universal driver of thermal tolerance in water breathing animals.

News story: www.trentu.ca/news/story/2...

Paper: journals.plos.org/plosbiology/...

Primer: journals.plos.org/plosbiology/...
More Oxygen Won’t Save Fish from Warming Waters
Trent study helps inform long-standing theory about increasing oxygen levels in higher water temperatures to support heat tolerance in aquatic species
www.trentu.ca
November 18, 2025 at 1:38 PM
Reposted by Graham Raby
cars-afs.bsky.social
CONGRATULATIONS!
Larkin Award, PhD Winner
#BradleyHowell
🪼
[Graham Raby, #TrentUniversity & Steven Cooke, #CarletonUniversity]
🪼
Bradley’s research focuses on using telemetry and respirometry data to assess #predatorprey interactions and movement patterns that raise predation risk.
November 2, 2025 at 1:04 AM
Reposted by Graham Raby
plosbiology.org
Oxygen limitation is considered a key mechanism of #ThermalTolerance. @dianasmadeira.bsky.social explores how a @plosbiology.org study challenges this idea, showing minimal protective effects of O2 supersaturation in heat-stressed #aquatic #ectotherms 🧪 Paper: plos.io/43hzMQa Primer: plos.io/3XeUtbS
The effects of temperature on organismal performance are depicted using thermal performance curves, where performance is greatest at the optimal temperature and starts to decrease toward cooler or warmer temperatures, reflecting the thermal window (tolerable range of temperatures) of the species. Briefly, the Oxygen and Capacity Limited Thermal Tolerance hypothesis proposes that oxygen limitation explains the performance decline at high temperatures and sets the first boundary for thermal limits across ectotherms. This is due to a mismatch between the oxygen demand of the organism and the capacity of the cardiorespiratory system to supply oxygen to tissues when the organism is under warming. This concept is central to predict species responses to warming. As oxygen supersaturation in water has been shown to alleviate oxygen supply limitations by increasing maximum rates of oxygen transport in blood, Raby and colleagues (2025) tested the effects of oxygen supersaturation on thermal tolerance across 14 aquatic species. The authors found that it had negligible effects on upper thermal limits, challenging the oxygen limitation hypothesis as a universal mechanism underpinning thermal tolerance of aquatic ectotherms. The authors highlight that oxygen supersaturation in water, a naturally occurring phenomenon in shallow waters, may not protect aquatic species from the effects of extreme heat.
November 6, 2025 at 5:30 PM
Reposted by Graham Raby
plosbiology.org
Oxygen supersaturation is proposed to buffer against #HeatStress in water-breathing animals. @graham-raby.bsky.social @jutfelt.bsky.social &co re-examine this question in diverse #aquatic #ectotherms, showing that #hyperoxia has minimal impact on thermal tolerance @plosbiology.org 🧪 plos.io/43hzMQa
Effect of hyperoxia (150% air saturation) on warming tolerance in 14 aquatic ectotherms from across the globe. Left: Forest plot showing effect sizes (model estimates ± 95% confidence intervals) for the effect of hyperoxia on warming tolerance. Black symbols are the fast warming (0.3°C min−1) trials, blue symbols are the slow warming (1°C h−1) trials, and yellow symbols are for a net combined effect with random effects for subgroups of the 24 experiments. The effects were considered statistically significant where the 95% confidence interval does not cross the red vertical line. Right: Approximate geographical distributions for the 10 species of fish (top) and four species of decapod crustaceans (bottom) used in the laboratory experiments to assess the effects of hyperoxia on upper thermal tolerance.
November 5, 2025 at 5:35 PM
Reposted by Graham Raby
plosbiology.org
Oxygen limitation is considered a key mechanism of #ThermalTolerance. @dianasmadeira.bsky.social explores how a @plosbiology.org study challenges this idea, showing minimal protective effects of O2 supersaturation in heat-stressed #aquatic #ectotherms 🧪 Paper: plos.io/43hzMQa Primer: plos.io/3XeUtbS
The effects of temperature on organismal performance are depicted using thermal performance curves, where performance is greatest at the optimal temperature and starts to decrease toward cooler or warmer temperatures, reflecting the thermal window (tolerable range of temperatures) of the species. Briefly, the Oxygen and Capacity Limited Thermal Tolerance hypothesis proposes that oxygen limitation explains the performance decline at high temperatures and sets the first boundary for thermal limits across ectotherms. This is due to a mismatch between the oxygen demand of the organism and the capacity of the cardiorespiratory system to supply oxygen to tissues when the organism is under warming. This concept is central to predict species responses to warming. As oxygen supersaturation in water has been shown to alleviate oxygen supply limitations by increasing maximum rates of oxygen transport in blood, Raby and colleagues (2025) tested the effects of oxygen supersaturation on thermal tolerance across 14 aquatic species. The authors found that it had negligible effects on upper thermal limits, challenging the oxygen limitation hypothesis as a universal mechanism underpinning thermal tolerance of aquatic ectotherms. The authors highlight that oxygen supersaturation in water, a naturally occurring phenomenon in shallow waters, may not protect aquatic species from the effects of extreme heat.
November 6, 2025 at 1:55 PM
graham-raby.bsky.social
Very exciting to finally have this work out there. Thanks to the team at @plosbiology.org for being willing to publish null results!
plosbiology.org PLOS Biology @plosbiology.org · 20d
Oxygen supersaturation is proposed to buffer against #HeatStress in water-breathing animals. @graham-raby.bsky.social @jutfelt.bsky.social &co re-examine this question in diverse #aquatic #ectotherms, showing that #hyperoxia has minimal impact on thermal tolerance @plosbiology.org 🧪 plos.io/43hzMQa
Effect of hyperoxia (150% air saturation) on warming tolerance in 14 aquatic ectotherms from across the globe. Left: Forest plot showing effect sizes (model estimates ± 95% confidence intervals) for the effect of hyperoxia on warming tolerance. Black symbols are the fast warming (0.3°C min−1) trials, blue symbols are the slow warming (1°C h−1) trials, and yellow symbols are for a net combined effect with random effects for subgroups of the 24 experiments. The effects were considered statistically significant where the 95% confidence interval does not cross the red vertical line. Right: Approximate geographical distributions for the 10 species of fish (top) and four species of decapod crustaceans (bottom) used in the laboratory experiments to assess the effects of hyperoxia on upper thermal tolerance.
November 6, 2025 at 3:03 PM
graham-raby.bsky.social
Special thanks to @dianasmadeira.bsky.social for authoring this thoughtful primer about the study we published this week in @plosbiology.org Good suggestions about all the work we still need to do to unveil the mechanisms underlying variation in thermal tolerance.

journals.plos.org/plosbiology/...
November 5, 2025 at 11:53 PM
Reposted by Graham Raby
plosbiology.org
Oxygen supersaturation is proposed to buffer against #HeatStress in water-breathing animals. @graham-raby.bsky.social @jutfelt.bsky.social &co re-examine this question in diverse #aquatic #ectotherms, showing that #hyperoxia has minimal impact on thermal tolerance @plosbiology.org 🧪 plos.io/43hzMQa
Effect of hyperoxia (150% air saturation) on warming tolerance in 14 aquatic ectotherms from across the globe. Left: Forest plot showing effect sizes (model estimates ± 95% confidence intervals) for the effect of hyperoxia on warming tolerance. Black symbols are the fast warming (0.3°C min−1) trials, blue symbols are the slow warming (1°C h−1) trials, and yellow symbols are for a net combined effect with random effects for subgroups of the 24 experiments. The effects were considered statistically significant where the 95% confidence interval does not cross the red vertical line. Right: Approximate geographical distributions for the 10 species of fish (top) and four species of decapod crustaceans (bottom) used in the laboratory experiments to assess the effects of hyperoxia on upper thermal tolerance.
November 5, 2025 at 2:07 PM
Reposted by Graham Raby
jaydebon.bsky.social
Very happy and proud to see this one published! Have a look at this global assessment of the effect – or lack of effect – of extra oxygen (hyperoxia) on ectotherm thermal tolerance! Led by @graham-raby.bsky.social and a team of incredible collaborators working on multiple taxa 🐟 🐠 🦀 🦐.
jutfelt.bsky.social Fredrik Jutfelt 🐠 @jutfelt.bsky.social · 21d
Oxygen supersaturation has been reported to protect aquatic animals from heat waves. We tested this in a large collaborative experiment on many species of fish and crustaceans. Our new paper in @plosbiology.org shows that the effect of hyperoxia on thermal tolerance is negligible. Unfortunately.
November 5, 2025 at 3:19 PM
Reposted by Graham Raby
jutfelt.bsky.social
Oxygen supersaturation has been reported to protect aquatic animals from heat waves. We tested this in a large collaborative experiment on many species of fish and crustaceans. Our new paper in @plosbiology.org shows that the effect of hyperoxia on thermal tolerance is negligible. Unfortunately.
November 5, 2025 at 10:34 AM
graham-raby.bsky.social
Boat salad
October 23, 2025 at 3:44 PM
graham-raby.bsky.social
We have the most photogenic campus
October 16, 2025 at 12:25 PM
Reposted by Graham Raby
garyburness.bsky.social
Excited about a new preprint from PhD candidate Megan Heft, showing that nestling provisioning rates in male tree swallows are not limited by the male's risk of overheating (in contrast with previous studies of females) 🧪 #ornithology #science
www.biorxiv.org/content/bior...
www.biorxiv.org
October 1, 2025 at 1:03 PM
graham-raby.bsky.social
If you're a fish tracking nerd you know and love the sight of this pink foam
September 26, 2025 at 6:23 PM
graham-raby.bsky.social
Caught a couple northern sunfish in a beach seine today; first time ever seeing these for me (in the Otonabee River near Trent U).
September 8, 2025 at 3:34 PM
graham-raby.bsky.social
tick tock
September 4, 2025 at 3:47 PM
Reposted by Graham Raby
methodsinecoevol.bsky.social
📖Published📖

Raby et al. provide a comprehensive, practical guide for designing and conducting experiments to measure critical thermal limits, with an emphasis on CTmax 🌍 🧪 👇

buff.ly/iZN6Xdg
Diagram of a template design for a CTmax apparatus. Aeration, mixing mechanisms (pump), and heating elements are in an ‘equipment section’ that is physically separated with a screen from the part of the arena containing the animals (‘animal arena’; here with fish). A submerged temperature sensor (or data logger) is used to log temperatures, in addition to a temperature sensor with a display that is used to score CTmax in real time. The time and temperature should only be visible to the data recorder (and/or video camera), not to the person observing animals for end points.
August 25, 2025 at 11:01 AM
Reposted by Graham Raby
jutfelt.bsky.social
Check out our new review on how to measure thermal tolerance! 🐟🌡️🧪
methodsinecoevol.bsky.social Methods in Ecology and Evolution @methodsinecoevol.bsky.social · Aug 25
📖Published📖

Raby et al. provide a comprehensive, practical guide for designing and conducting experiments to measure critical thermal limits, with an emphasis on CTmax 🌍 🧪 👇

buff.ly/iZN6Xdg
Diagram of a template design for a CTmax apparatus. Aeration, mixing mechanisms (pump), and heating elements are in an ‘equipment section’ that is physically separated with a screen from the part of the arena containing the animals (‘animal arena’; here with fish). A submerged temperature sensor (or data logger) is used to log temperatures, in addition to a temperature sensor with a display that is used to score CTmax in real time. The time and temperature should only be visible to the data recorder (and/or video camera), not to the person observing animals for end points.
August 25, 2025 at 1:16 PM
Reposted by Graham Raby
thefsbi.bsky.social
#JFB: Validation of a new acoustic telemetry transmitter for the study of predation events in small fishes doi.org/10.1111/jfb.15827 #FishSci
doi.org
August 23, 2025 at 3:27 PM
graham-raby.bsky.social
is this what the discovery grant panel looks like
August 22, 2025 at 10:46 PM
graham-raby.bsky.social
Incredibly nerdy paper, but should be useful I think.

This was a product of a pre-SEB writing retreat a bunch of had in Czechia last year.
August 21, 2025 at 4:36 PM
Reposted by Graham Raby
jaydebon.bsky.social
Raby lab retreat this week at Harkness Lab of Fisheries Research was a great success!

Thanks to the ghost of F.E.J. Fry for writing inspiration 👻🐟
August 21, 2025 at 1:01 PM