Fishermen running from enemy ships...

[Handel]

When an enemy ship approaches a coastal city, the fishermen run away from the water. The problem is they become specialists and the city starts to starve. There are free shore tiles wich produce food, butr nevertheless they become specialists. I guess if I put the governor on food producing, this will not happen. But I don't want the cities to be concentrated on food producing... And I don't get a warning when a city starts to starve, so I have manually to check every city where enemy ships arrives and manually to remove the specialists.
Any advices about this problem?

[vmxa1]

You have a signal. The color changes from gree to white for no growth or pink. In any event you can see something is up.

Also when an enemy come to your area, you should be alert to check on the town.