Answer
He is likely suffering from basal cell carcinoma, which is form of skin cancer that is caused by long exposure to the sun.
Work Step by Step
Since he has ulcers on his forearms and face, it is likely he has basal cell carcinoma. Because these parts are generally exposed to sun, and the occupation of fisherman is an outdoor one. The ulcers developed by basal cell carcinoma are small and round and they have a shiny translucent surface. These ulcers grow slowly.
