I have a saltwater fly line that has 2 abrasions - one at about 45 feet and one about 50 feet (those oyster beds are nasty!). Each is about 6 inches long. The abrasions are tiny nicks in the line and aren’t readily noticeable just by looking at the line - but you can feel them when stripping line in.
Anything I can do with it, short of replacing the entire line?
Time to buy a new line.
nope !!! ur screwed ! get a new line
While fishing one day last year as I was stripping my fly back, I felt a spot on my fly line. Upon looking at it, I decided that I must have stepped on it at one time or another. I did not want water to get into the fly line core through this knick, so, I got my Loon’s Knot Sense out and put on a very small drop on that spot and let the sun cure it and went back to fishing. That was last year and I am still using that fly line with no problems. The funny part is that the knick is at about 30 feet up the fly line and just about everytime I feel that very smooth bump come through my stripping fingers I will get a hit!! 
So, now I use that repair bump as my signal to pay attention, you are about to get a hit!! Loon’s Knot Sense might be something that will work for you. It sure won’t hurt anything to try it. The repair with it is leaves a very smooth surface and it seems to hold real well.
MNFisher:
I have successfully buffed out minor abrasions and rough spots on fly lines using a combination of a [url=http://solutions.3m.com/wps/portal/3M/en_US/Scientific_Anglers/Fly-Fishing/Products/Accessories/Floatant_Dressing/FlyLineCleaningPad/:8e34b]Sci Anglers abrasive line cleaning pad[/url:8e34b] followed by brisk rubbing with a dry cloth.
As long as the abrasion doesn’t go all the way down to the core the line still should be fishable. The line coating is PVC and also can be smoothed out with a CAREFUL application of heat which will melt and smooth the coating.
Always save old fly lines for experiments. I have amazed myself with what can be done to salvage a line for at least SOME more use.
Unless you can see the core, the line is fine. Just put a couple of coats of pliobond on the nicks.
I can also HEARTILY endorse the shrink tube method.
Been there, done that and it WORKS!