Splice into arcane

[Maxpayne03]

If my opponent cast {Nourishing Shoal} Then splice into arcane {Through the Breach}, do I have priority to use {Surgical Extraction} on the breach in his graveyard before he splice?

[Splicer]

If my opponent cast {Nourishing Shoal} Then splice into arcane {Through the Breach}, do I have priority to use {Surgical Extraction} on the breach in his graveyard before he splice?

Yes, but you won't have seen it in his hand. After he splices, you won't have a chance to stop it.(Unless you counter the Shoal)

[Kaylesh]

If my opponent cast {Nourishing Shoal} Then splice into arcane {Through the Breach}, do I have priority to use {Surgical Extraction} on the breach in his graveyard before he splice?

Yes, but you won't have seen it in his hand. After he splices, you won't have a chance to stop it.(Unless you counter the Shoal)

To add: he splices as he casts the spell, at that time you can't respond. Once the spell is cast, you receive priority, then you can extract, but it won't effect the spliced shoal.