Gelcoat is slightly less flexible than
fiberglass, over time it gets even less flexible, thus can get those spider cracks that are just surface deep.
Sealing as Raz suggests and keeping an eye on them is a good approach. Impact cracks that radiate out from point of impact or bulls eye cracks that are in concentric circles around impact warrant some checking to see if fiberglass under gelcoat has any damage. Or at least a little closer monitoring.