Being an animal guy myself, initially I was like, there's got to be a better option than shooting. Then I read the rest of the story, about a firefighter afraid for his life and occasionally having to shield himself with his bike against these dogs, and I'm less interested in saving the dog's lives than I am with a dedicated public servant's life. I say either shoot the dogs, but given that even a really good shot shooting backwards on a bike while riding downhill is sketchy, I'd contribute $20 to getting you a bottle of this:

http://www.amazon.com/SABRE-FRONTIER.../dp/B000H7N26A

Easier to spray that all behind you than it would be to be accurate with a pistol, even at short range. A worse situation would be you shooting, and losing focus on controlling the bike and crashing while the 6 remaining dogs decide to continue and have you for breakfast.

And having heard stories of dogs returning home on foot from thousands of miles away, I just get the feeling that relocation will be a stopgap measure.