The 19-year-old father of 12 offspring through three different females - Farah, Tiffy and Soda - showed signs of tiredness at around midday on Monday, the southern city said in a statement.
"Mike could no longer get out of the pool and was brought ashore by staff. The extremely weakened animal was treated by a vet but died from acute heart failure around 3:30 pm," it said.
"Mating season is a common time for fatalities when bulls often stop eating for days to devote themselves fully to mating. For sea lion bulls with a harem this is the most exhausting time," it noted.
The statement added that Mike's offspring can be found in zoos as far afield as Berlin, Spain and the Netherlands, and that the 285-kilo (550-pound) animal was so "good natured" that people could touch him.
"He will be remembered fondly by visitors of the animal park for his appearances during shows in the dolphinarium where he had close contact with the dolphins," it said.
The record age for a sea lion in captivity is 30. In the wild they have a life expectancy of 17.