It depends on the situation.
The number of trips required to qualify for a pilotage certificate will depend on the particular origin and destination pairing, in accordance with the level of risk to navigational safety.
Those transits are set in order to ensure that the experience level a licensed pilot has is equivalent to the bridge crew operating that vessel. It's really based on the principle that someone who conducts the same transit over many years has the same level of knowledge and experience as a marine pilot, with respect to the licensed pilot. In some sense, the experience and the knowledge of the bridge crew are equal to that of a licensed marine pilot; therefore, they can apply for a certificate.
However, the certificate only applies to a very specific set of origin and destination pairings. They don't become a licensed pilot eligible to navigate anywhere in the St. Lawrence. A pilotage certificate is only valid for a certain port of origin and a certain destination.