A person who has participated in a survey.
People that are employed are 'employees'. People that are interviewed are 'interviewees'. Seems only right that people who are surveyed are called 'survees'.
'Over 60% of survees under the age of 7 said they preferred to sleep with a night light.'
'She was a survee who gave false information.'
'The majority of survees indicated that they disliked the taste of marmite, though my guess is they didn't eat it the right way.'