GONEFISHING Try using the "Scan Offset" settings in the preferences to center the captured bobber area around the base of the bobber, rather than the feathers. This usually involves moving the captured area to the left (negative x offset) and down a bit (negative y offset). You'll have to play around with the numbers to find good values for your screen resolution.
While the feather color is great for identifying the bobber itself, the base is the most distinctive area that changes when a fish is caught (ie, it disappears around the *splash*). Centering the scan area on the base, as well as expanding the scan radius if necessary, will help GoneFishing to accurately determine when a fish is caught.
I hope that helps.
(Version 1.1.2)