01/11/2021
Those who follow this page may realise I'm often discussing and pondering trout vision.
Here is some further information on how the process of how these images were created for those who seem to be doubting the validity of the images. (which is fine if its valid but "a trout ate my size 20 midege from 6 feet, your wrong" isn't exactly a good counter point or even opposing what is shown here)
Visual Acuity in all species is measured in arc minutes. The lower the number of arc minutes (or seconds) the greater detail one can see. A study on rainbow trout found rather conclusively that they see with a visual acuity of 14 arc minutes. This is the study cited in the image. While it is a study from 1979 the methodology that was used is still used in visual acuity studies of other species today. So the figure of 14 minutes of arc definitely holds some credibility from a scientific perspective.
Once you have the number (14 minutes) it is possible to model a trouts visual perspective using some more modern technology that has been widely used to model other species visual perspectives. I will cite this here for anyone interested, the study shows a number of animals visual perspectives based on their visual acuity.
So by using these two resources you are able to create an image with some level of confidence that is atleast in the ball park of rainbow trouts visual perspective.
A common question I’ve had…
A fish travelled 6 feet (or more) to take my fly, how’s that possible based on your images?
This is only measuring acuity which is the detail a species can see. Just because they cannot see the detail of the fly they can still see the general profile, shape and size from a good distance which is often enough to atleast have them come closer for a look. You will notice often trout will turn away at the last minute, I think this may be due to the fact they got close enough to see it wasn’t the real deal hence the last minute rejection.
Also in the fish world compared to other species 14 minutes of arc is a very high level of acuity.
Study mentioned above:
Caves EM, Johnsen S. AcuityView: An r package for portraying the effects of visual acuity on scenes observed by an animal. Methods Ecol Evol. 2017;00:1–5
Looking to make this into something user friendly that we can all use.