A vessel greater than 100m in length is engaged in fishing at anchor in restricted visibility. What fog signal should she sound?

When a vessel greater than 100 meters in length is at anchor and engaged in fishing in restricted visibility, it is required to sound a specific fog signal to ensure that other vessels can detect its presence.

In restricted visibility, a vessel at anchor is obligated to sound one prolonged blast at intervals of two minutes. This is a standard signal to alert other vessels of its location and status, as indicated in the International Regulations for Preventing Collisions at Sea (COLREGs). The signal promotes safety by ensuring that a large, anchored fishing vessel can be noticed by approaching vessels that may also be navigating in restricted visibility conditions.

The other signals mentioned would not be appropriate for a fishing vessel at anchor under these specific circumstances. The different options could pertain to other situations, such as moving vessels or vessels engaged in other types of activities, but the rule for a vessel at anchor clearly specifies the sound to be one prolonged blast every two minutes. This helps maintain clarity and uniformity in communication amongst vessels operating in restricted visibility.