Image copyright Brent Just Image caption Canadian football is very similar to American football, except for a few different rules

On paper the sport of Canadian football, the lesser-known, much poorer, northern cousin of American football, should be struggling to exist.

Not only does it have to compete with Canada's obsession with ice hockey, but it has the goliath that is American football's National Football League (NFL) just across the border.

And by any measure you care to check - such as the value of TV deals, team revenues, and player salaries - Canada's professional gridiron competition, the nine-team Canadian Football League (CFL), barely bumps the needle.

For example, annual TV revenues at the NFL total more than $5bn (£3.2bn) per year, compared with just $32m at the CFL.

Meanwhile, the annual turnover at the richest CFL club, the Saskatchewan Roughriders, was $55m in 2003, while the NFL's Dallas Cowboys made $560m, and the Toronto Maple Leafs hockey team secured $190m.

Yet with the 2015 CFL season now under way, Canadian football has actually never been in better health.

Image copyright Jeff Vinnick Image caption Canadian football's version of the Super Bowl is called the Grey Cup

The current TV deal, first signed in 2013 and recently extended, is double the previous agreement.

And teams have seen their profits skyrocket - the Edmonton Eskimos recorded a 2014 profit of $2.8m, twice that of 2013, and it is a similar situation at other clubs.

CFL commentators, team owners and fans put the continuing success of the sport down to one central thing - a loyal core of passionate supporters.

'Cultural differences'

The sports of American and Canadian football both developed in the mid-19th Century, evolving from the British game of rugby.

While the two forms of gridiron are in essence the same game, there are some key rule differences. For example, Canadian football has larger pitch measurements, and one more player per side.

Image copyright Jeff Vinnick Image caption Fans of Canadian football are a fun and characterful bunch

Brad Humphreys, a sports economist at the University of West Virginia, who spent several years at Canada's University of Alberta, says the CFL benefits greatly from the strong desire of Canadians to maintain a separate identity to the US.

"Canadians are acutely aware of the cultural differences [between the two countries], and acutely interested in maintaining their own separate cultural identity," he says. "The CFL is one way they can do that."

David Holmes, 51, a lifelong fan of Vancouver's CFL team, the BC Lions, happily points out that the first recorded game of Canadian football took place in 1861, eight years before the first documented American football match.

He says that the Canadian game's long history and heritage is a big part of what keeps fans coming back.

Image copyright David Holmes Image caption A youthful looking David Holmes photographed at a BC Lions home game in 2011

"That's probably one of the things that carries me forward with avid support of the BC Lions," he says.

Like many other committed fans, he adds that he caught the bug thanks to his parents taking him to games from a young age.

Mr Holmes says: "I have really, really strong memories and associations from when I was young. I collected player cards and autographs, and I've sort of kept up with that. I have a massive collection of them."

He also says that Canadian football players are better athletes than their counterparts in the US.

"The athletes, I think, have to be in better shape to play the CFL game. It's kind of a faster game than the NFL."

'Different levels'

At the Saskatchewan Roughriders, one of three CFL teams to be owned by their fans, a lack of local competition from other sports gives the club an advantage over its league rivals.

The club's chairman, Wayne Morsky, says: "We're fortunate that there are no other professional sporting teams in the province [of Saskatchewan]. There is no hockey team, no baseball team, no soccer team."

Image copyright Rich Lam Image caption Canadian football is as high impact as its American cousin

Mr Morsky adds that his team, which is based in the city of Regina, the capital of Saskatchewan, also benefits from Canada's high level of internal migration.

"There are also a lot of expatriates who live throughout the country, particularly to the west of us," he says. "When we are visiting in Calgary or Edmonton [in the province of Alberta], it's close to a 50-50 split in the crowd. It's that connection."

Gridiron differences

The Canadian field of play is 110 yards long by 65 yards wide (101 m by 59 m), rather than 100 yards long by 53.3 yards wide in American football

Canadian teams have 12 players on the field per side, while there are 11 in the US

In Canadian football teams have three attempts to move the ball forward by ten yards, compared with four in the American game

In Canadian football the gap between the main lines of the offensive and defensive teams at the start of each play has to be one yard. It is less than a third of this distance in American football

Rod Smith, a veteran presenter on Canadian sports TV channel TSN, says that CFL also thrives in part because it doesn't try to compete with the NFL.

"I don't like the either-or aspect of it," he says. "I don't think it's mutually exclusive for a football fan. You can love both leagues.

Image copyright TSN Image caption Broadcaster Rod Smith says it is wrong to criticise the CFL for being much smaller than the NFL

"I resent not only NFL fans who think the CFL is not as good by comparison, but CFL fans to bash the NFL for whatever reason. Both are very good brands of football.

"The NFL is bigger money. A lot of things about it on a much grander scale.

"But to necessarily assess something's value strictly based on how much money it makes and how many people watch it is misguided. I really think it is possible to be good at different levels."

Yet the CFL is not without some challenges. Two players have recently filed a 200m Canadian dollar ($160m; £100m) lawsuit against the league due to concussions they say they sustained during matches.

Image copyright Jeff Vinnick Image caption Some CFL followers say it should be doing more to attract younger fans

Mr Morsky adds that the CFL has to do more to follow the NFL's lead and turn every game into a full-day event."The NFL has done a fantastic job of that with tailgating, and we're doing more and more of that," he says.

But perhaps the biggest issue for the CFL going forward is the age of its fanbase.

According to Rod Smith, the league isn't doing enough to attract more young fans.

"It's a particular problem in the bigger markets [like Vancouver and Toronto]," he says. "That's something that the league is concerned about.

"They want to reach a younger demographic for obvious reasons. But how they do it? That's a big question."