I was asked at work how I could tell the difference between a male and a female muskie. The first thing that came to my head was "females get bigger". So if you get a 50" muskie, you can pretty much say "It's a female", but what about all of the others?
I found a good website that had a graphic. (See http://www.lakescientist.com/2010/muskellunge ). This graphic shows the difference between the anus/vent area of the males and females. I then set out to take pictures of the anus/vent area of the fish I would catch. (The vent is used either excrete eggs or sperm.) Of course, as muskie fishing goes, it wasn't until a couple weeks later that I and two friends caught four fish. We took the necessary pictures. I then looked at them and didn't feel I had the expertise to make the call. I emailed the pics to the Maryland DNR. They made the call. Now, with what the DNR shared with me, I feel I can make some good identification of the fish I catch. I imagine there will be the close calls that I might not get correct. These close calls may be immature fish, as I think the mature fish will be somewhat similar to those below.
Pictured below are three of the pictures that we took of the fish we caught on 12/31/2010 and 01/01/2011. I've given the anus width in blue, and the vent width in red. You can see how much wider the female's vent is compared to her anus. In the single male picture, the vent is almost the same width as the vent. Also include is the graphic contained in the above web article.