As compared to what? What city is a hockey market, by your definition?
Do yourself a favour and Google "GTHL" - it's the world's largest hockey league, and it's in Toronto. Within the GTA you have over 30,000 kids participating in Minor Hockey, dozens of arenas and adult leagues, and multiple Jr A franchises and college teams. A conservative estimate would be that 100,000 to 200,000 Torontonians play hockey at some level. But, I suppose that's not enough to qualify as a "hockey market" ?
Perhaps it would be a "hockey market" if you include nearby cities like Guelph, Kitchener, Barrie, Hamilton, and Oshawa, all of which provide strong support for Major Junior / AHL teams.
The reality is this: Torontonians don't want to fight traffic and drive 40+ minutes to the Ricoh Centre to watch the Marlies play. That does not mean it's not a hockey market, it just means that they don't want to fight traffic to watch the Marlies play because the arena is not conveniently located for the target market: families who live in the suburbs.