Sport is defined as:
sport
[ch8194] [ch8194]/sp[ch596]rt, spo[ch650]rt/ Show Spelled[spawrt, spohrt] Show IPA
noun
1.
an athletic activity requiring skill or physical prowess and often of a competitive nature, as racing, baseball, tennis, golf, bowling, wrestling, boxing, hunting, fishing, etc.
Define Athlete:
ath·lete
[ch8194] [ch8194]/[ch712]æ[ch952]lit/ Show Spelled[ath-leet] Show IPA
noun
a person trained or gifted in exercises or contests involving physical agility, stamina, or strength; a participant in a sport, exercise, or game requiring physical skill.
If you go by definitions then a professional fisherman is an Athlete. He is trained (and most are gifted) in an activity requiring skill, therefore he is an athlete.