I have friends working for few Ottawa's AYCE sushi restaurants before. I am told that all tips from customers do not go to the servers' pockets. All tips go to the owners!
The servers are paid on a per day basis (some are paid CASH). This include some of the kitchen staff. The trick is only one server knows to speak fluent English. Others' English are not so good. They can get a job in Ottawa, they are very happy already.
So, don't bother with higher tips if you go there to eat.
Besides, why you want to go to eat raw sushi/sashimi in AYCE sushi place? I worry about the cleanliness and how the kitchen staff handles the raw food. Do you know the 50% of Asian have H. Pylori (幽門螺旋菌) and mostly from eating raw food. If you want to eat sushi or sashimi, pay few more dollars to go eat in a traditional Japanese restaurant.