Effects of incubation temperature on the upper thermal tolerance of the imperiled longfin smelt (Spirinchus thaleichthys)

Upper thermal limits in many fish species are limited, in part, by the heart’s ability to meet increased oxygen demand during high temperatures. Cardiac plasticity induced by developmental temperatures can therefore influence thermal tolerance. Here, we determined how incubation temperatures during the embryonic stage influence cardiac performance across temperatures during the sensitive larval stage of the imperiled longfin smelt. We transposed a cardiac assay for larger fish to newly hatched larvae that were incubated at 9, 12, or 15 ℃. We measured heart rate over increases in temperature to identify the Arrhenius breakpoint temperature (TAB), a proxy for thermal optimum, and two upper thermal limit metrics: temperature when heart rate is maximized (Tpeak) and when cardiac arrhythmia occurs (TArr­). Higher incubation temperatures increased TAB, Tpeak, and TArr­, but high interindividual variation in all three metrics resulted in great overlap of individuals at TAB, Tpeak, and TArr­ ac..., , , # Effects of incubation temperature on the upper thermal tolerance of the imperiled longfin smelt (Spirinchus thaleichthys)

[https://doi.org/10.25338/B8H06D](https://doi.org/10.25338/B8H06D)

Contact: Yuzo Yanagitsuru, [e-mail], [e-mail]
All analyses were conducted in R version 3.6.3
File: LFS\_cardio\_breakpoint.R includes script that calculated all breakpoint temperatures
File: lfs\_cardio\_stats.R includes script for statistical analyses.

Description of column headers
File: Heart\_rates\_compiled.xlsx

'Analyzed dataset' includes data that were used for analyses.
'with missing measurements' includes data that were incorrectly assayed (temperature steps were missing during assay)

* Date - Date assay conducted
* ID - Individual fish identification number
* Clutch - Clutch/cross identification (i.e. ID for different pairs of male/female broodfish)
* Temperature - Temperature in degrees Celsius that heart rates were measured
* Acclimation - Incubation tem...