some radar questions



I am working on a project that utilizes a radar and an open array antenna.
The antenna is installed on the land to monitor a fish farm in the sea which is located at a distance 1300meters from the land (where the radar antenna is installed).

1.How to restrict the angle of firing
From the images I can see that the antenna is firing 360 degress and this may have side effects to the health of the employees who work on land near the antenna. How can i restrict this and make the antenna fire only for 90-100 degrees towards the area where the fish farm is located? How this feature is called and is it available on all models?

2.The radar operated around 2500 hours and the magnetron should be changed every some hours. A Guard Zone was configured and after a year of operation the users claim that the farm is shown more up on the screen than before. Is there any chance that farm is shown farther than before 1 year due to the fact that magnetron deteriorated? I know that due to deterioration it can show worst in big distances but can it show the targets farther than they appeared before because of deterioration?

3. I am setting a guard zone around the farm monitoring if a boat is coming in the zone to raise an ALARM and it continuously ring and this is because of the farm that exists in the zone (that's what i understood). Is there any way to set an alarm to monitor only the boats and not just to check if there is anything in this zone?

4. The fishermen claim that the radar is scaring away the fish in the area. I know that this may sound stupid but is there any sense on this?
Can you please tell us what model Furuno radar you are using?