What's your workflow? These look like errors you get from changing the lowpoly mesh after baking. Did you export your highpoly out of Zbrush and bake in Maya, or somewhere else like Xnormal? Did you make any changes to your lowpoly after baking the map? Any overlaps in your lowpoly UVs? Any UV mirroring?
I would suggest not baking in Zbrush. Xnormal or Maya will do a better job with an exported model. I haven't baked normalmaps in Zbrush, but it looks like the gaps are places where the raycasting failed, where the baker couldn't "see" the highpoly surface for some reason. Could be overlaps, could be ray distance, dunno.…