Spending a penny has cost Kerrin McEvoy $500 at Randwick with the leading jockey fined after being caught short.

McEvoy ducked into a barrier to relieve himself before the second race but his actions were caught on television.

The barriers were also in front of the grandstand for the 2400m race and stewards told McEvoy it was a bad look for the sport and he should have been aware he could be seen.

McEvoy pleaded guilty to the misconduct charge.

"I was supposed to ride light today and when Capitalist was scratched I re-hydrated," McEvoy said.

"I needed to go. I wasn't anticipating the cameras."

Chief steward Marc Van Gestel said had it not been for McEvoy's clean record and standing in the industry the penalty would have been greater.

"You have got to accept in this day and age there are cameras around," he said.

"We think the conduct is out of character and if your record and standing in the industry wasn't what it is, the fine would have been greater."

McEvoy's percentage for his win aboard Knit `N' Purl will more than pay the fine.