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Rainbow trout vision: the science and the numbers

Oncorhynchus mykiss · order Salmoniformes · Fish: all the numbers

The rainbow trout has 5 colour channels, including violet.[1][2][3] Its sharpest vision resolves 4.29 cycles per degree, against 63.75 for people in this dataset.[7] The rainbow trout stops seeing flicker at 27.1 Hz, against 60 Hz for people.[28][29]

See it on your photoBack to How does the rainbow trout see?
  • 5colour receptor classesMeasured*
  • 4.29cycles per degree (sharpness)Measured
  • 27.1hertz flicker fusion (motion)Measured

The rainbow trout (Oncorhynchus mykiss) is a fish in the order Salmoniformes. Its eyes belong to the vision type Shallow-water fish tetrachromat: four cone types including ultraviolet and far red. Measured in this species: colour, sharpness and motion (flicker fusion). Measured core: measured values on at least 3 of the 6 dials.

This is a simulation built from published eye measurements, not what the animal experiences.

Method: How we know what animals see (the See Like Animals vision engine) · Sources · Last updated . Every value below carries its evidence level and sources; nothing is typed by hand.

What the rainbow trout sees: colour receptors

Rainbow trout colour receptor peaks, 300 to 700 nmRainbow trout: 5 receptor peaks at 416, 453, 514, 530, 570 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Rainbow trout: 416, 453, 514, 530, 570 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • It has 5 colour receptor classes; people have 3.
  • Its sharpest vision resolves 4.29 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • It stops seeing flicker at 27.1 Hz, against 60 Hz for people in this dataset, so fast motion looks choppier to it.[28][30]

The six dials

Evidence levels: how the tiers work. "Measured" means a value measured in this species; "Estimated" values come from a close relative or an eye-size formula. The last column gives the values for people from the same catalogue.

Vision values for the rainbow trout (Oncorhynchus mykiss), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
5 receptor classes: 416 nm (VS/SWS (violet)), 453 nm (SWS (blue)), 514 nm (MWS (green)), 530 nm (MWS (green)), 570 nm (LWS (long))
measured in this species
Measured (not re-verified)[1][2][3]Colour receptors: 3 receptor classes: 421.5 nm (VS/SWS (violet)), 532 nm (MWS (green)), 558.4 nm (LWS (long)) Measured (not re-verified)[4][1][5][6]
SharpnessAcuity
4.29 cycles per degree
median of 1 behavioural rows (method priority rule)
Measured[7]Acuity: 63.75 cycles per degree Measured[8][9]
Field of viewBinocular overlap
32.85°
group default: median of tier-A values in vision type the "Shallow-water fish tetrachromat" type within phylum Chordata (2 species: Danio rerio, Notemigonus crysoleucas)
Group default[10]Binocular overlap: 122.5° Measured[11][12]
Total field of view: 200° Measured (not re-verified)[13]
Blind area behind the head: 160° Derived[13]
Eye placement: frontal Derived[11][12]
Sharp zones (foveas)Number of foveas
0
group default: mode of tier-A values in vision type the "Shallow-water fish tetrachromat" type within phylum Chordata (2 species: Toxotes jaculatrix, Anableps anableps)
Group default[14][15]Number of foveas: 1 Measured[16]
Fovea type: fovea Measured[16]
Fovea type
ventrotemporal area (high rgc density)		Group default[14][15]
Night visionActivity pattern
diurnal
group default: mode of tier-A values in vision type the "Shallow-water fish tetrachromat" type within phylum Chordata (224 species: Amphiprion ocellaris, Acanthochromis polyacanthus, Acanthurus bahianus, Acanthurus…
Group default[17][18]Activity pattern: diurnal Measured (not re-verified)[19][20][21][4][22][23][24][18]
Pupil shape: vertical Group default[25][26]
Reflective layer (tapetum): no Measured[27]
Rods vs cones: cone-dominated Derived[19][20][21][4][22][23][24][18]
Rods vs cones
cone-dominated		Group default[17][18]
Motion (flicker fusion)Flicker fusion frequency
27.1 Hz
median of 2 rows (no bright-light flag) (behavioural/whole-eye ERG rows; all rows: [27.0, 27.1])
Measured[28][29]Flicker fusion frequency: 60 Hz Measured[28][30]

All fish side by side: Fish: every measurement. Method: how we know what animals see.

Sources

  1. Kirwan
  2. Schweikert et al. 2018
  3. VPOD in-vivo (MSP / single-cell) lambda… 2025
  4. Longcore 2023
  5. Müller et al. 2009
  6. Thermal Activation and Photoactivation of Visual… 2004
  7. Caves et al. 2017
  8. Kirk et al. 2004
  9. Veilleux et al. 2014
  10. Pita et al. 2015
  11. Heesy 2004
  12. Heffner et al. 1992
  13. Campbell & Green 1965
  14. Schwab et al. 2001
  15. Temple et al. 2010
  16. Kopania et al. 2025
  17. Froese et al.
  18. Moura et al. 2024
  19. Anderson et al. 2017
  20. Borges et al. 2018
  21. Wilman et al. 2014
  22. Maor et al. 2017
  23. Jones et al. 2009
  24. Schmitz et al. 2011
  25. Banks et al. 2015
  26. Cervino et al. 2021
  27. Guareschi et al. 2025
  28. Healy et al. 2013
  29. Lafitte et al. 2022
  30. Inger et al. 2014

Every value cites its sources (all sources). Values were extracted from these works and converted (units, medians, derived values); changes are ours, and the listed sources do not endorse this site. Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this? Method: how we know.