Is this only on one frame, about 3-4 from the end of the roll? If it is only on one roll, it's obstruction of the liquid flow caused by the very end of the film coming really close to contacting the film on the reel below it. I had this problem (albeit not nearly as severe), and resolved it by folding the very edge of the film up and away from the reel as I load it.
If it's on every frame, then I would say you have a light leak in your camera.
What kind of camera is it?Does it have a detachable back?Hasselblad?Bronica?Looks like the leak starts at the top and tapers off toward the bottom.Judging by your photo.
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