See the links below as they appeared in the press. While more may emerge on the event itself, it is interesting to compare these two news reports. Both would be based off of the same press release (issued by they Yukon Coronor's office), but they take a different tack, especially with the story headline.
It is noteworthy that the Whitehorse News report omitted the outfitter's name, while the CBC included it.
This is also the first time I have seen a coroner using "a witnessed drowning" as grounds for no further investigation. I can think of three "witnessed drownings" in Ontario that did follow with a coronor's investigation.
http://www.cbc.ca/news/canada/toronto/story/2011/07/15/yukon-canoe-capsize-death.html
http://www.whitehorsestar.com/archive/story/no-further-investigation-planned-into-mans-death/