I give Jenny salmon oil daily for her coat (and all the other benefits of good omegas). When I adopted her, her coat was dull, she hadn't been groomed regularly, and she was shedding huge clumps of dry fur--the salmon oil has definitely helped. Her coat is so soft and shiny now.
You do have to be careful when you introduce salmon oil in terms of starting gradually so as not to have diarreha and you might have to give a little less food to prevent weight gain. It also takes a couple of weeks to notice the difference.