Which of the following tactics is generally advised if a crew member encounters a suspicious vessel?

When encountering a suspicious vessel, the advised tactic is to gather information and report to the command. This approach prioritizes the safety of the crew and the overall mission. By collecting data such as the vessel's registration, behavior, and any observable activities, crew members can provide critical details to command that can aid in assessing the situation and determining the appropriate course of action.

This tactic allows for a thorough evaluation of the vessel and the context in which it is operating. Command can then make informed decisions, potentially coordinating with other assets or law enforcement if necessary. Effective information gathering also helps avoid unnecessary escalation and ensures that the situation is addressed in a measured and organized manner.

The other options do not align with best practices in maritime security and tactical operations. Launching an immediate attack could lead to conflicts that might escalate beyond control without proper justification. Ignoring the vessel dismisses potential threats that could harm the mission or crew. Signaling the suspicious vessel to leave the area could provoke a reaction without understanding the situation, which also could lead to unpredictable outcomes. Thus, gathering information and reporting to command not only adheres to established protocols but also enhances crew safety and operational effectiveness.