Buffering line segments that intersect another segment using a specific field value

[ZacharyKasson]

I have a field (Fish) that scribes whether a stream has fish (dark blue - 100 ft buffer) or no fish(light blue- 35 ft buffer for 500ft upstream of fish stream). I'd like to buffer nonfish streams that touch a fish stream for 500 feet with a different buffer value. Currently I am visually finding nonfish streams, measuring 500 ft from the fish stream, splitting the stream at that point, updating the buffer field of that newly split segment, and finally running the buffer on the layer. 

This is very time consuming and I am hoping there is a faster way to do this. I am pretty good at creating geoprocessing tools with python but have not worked much with the buffer tools. Any ideas are appreciated!

[DanPatterson]

Are you using

Create point features along a line—ArcGIS Pro | Documentation

or this

Generate Points Along Lines (Data Management)—ArcGIS Pro | Documentation

 to create the points?

Then splitting the lines with

Split Line at Point (Data Management)—ArcGIS Pro | Documentation

and using this

Multiple Ring Buffer (Analysis)—ArcGIS Pro | Documentation

to create the buffers?

[ZacharyKasson]

I was just using the built in measure tool to follow the line, then split the line using the split tool. Those tools definitely seem useful. Thank you for mentioning those.