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## Using Tracker to measure fish swimming speed in the wild post and replies

Is it possible to measure fish swimming speed in the wild with Tracker? - June 22, 2015 at 5:24
Molly Scott
1 Posts

Hey everyone,
I am a PhD student studying fish swimming speeds. I only came across Tracker from a paper I read today and was hoping to get some information/advice about capabilities of Tracker.

Basically, I am looking for a method to estimate fish swimming speed in the wild in meters/second or bodylength/sec. I would like to use video to film individuals swimming for a certain amount of time (10s) and get estimations of distance and hence swimming speed-
1) Is this possible using Tracker?
2) Is tracker able to give estimates of fish size as well as speed?
3) And can Tracker estimate distance/swimming speed if the start frame and end frame are completely different, i.e. have no points of reference in terms of habitat for measuring distance? My fish species are apex predators who are quite fast swimmers.

### Replies to Is it possible to measure fish swimming speed in the wild with Tracker?

Re: Is it possible to measure fish swimming speed in the wild with Tracker? - June 24 2015 11:49

lookang
220 Posts

1 Yes it is possible using Tracker but within error limits that the fish are moving perpendicular to the line of sight. this can provide you an estimate of the fish swimming speed in the wild in meters/second (you need a unit of measure in the video at the position of fishes) or bodylength/sec (perhaps you do not need a ruler of sorts).

2 i recommend you use something in the video as a unit of measure to calibrate against the fishes body length. If so , tracker can give estimates of fish size as well as speed

http://weelookang.blogspot.sg/2015/06/tracker-motion-of-person-progressive.html

use ruler to calibrate length

3 for a moving camera reference frame, you need to tell Tracker what is constant, a rock that is to be used as origin (0,0) or else nothing can help in completely different/ or no points of reference in terms of habitat for measuring distance?

http://weelookang.blogspot.sg/2015/06/tracker-constant-acceleration-of-050.html

use a fixed object as reference origin (0,0)

In summary, you need to be scientific (reference length, fixed camera point, fixed object to be used as origin(0,0) ) about your video taken in order for the results to be scientific (repeatable and accurate). else, it is not going to yield data on the speed of fish correctly in the wild.

Post edited June 24, 2015 at 11:57 PM EST.

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