There isn't any real way to determine the sex of a walleye except during pre-spawn when the females have a largish gut and the males are very obvious by the milt. Having said that, you can bet the large walleyes you catch or see are females. Males run smaller and are more aggressive during the pre-spawn period.

However, I know of a 10-pound walleye that was caught in Roosevelt about 15 years ago, so size isn't a perfect determinor.