When fishing at the Holo House, you catch extra bonus fish if you successfully catch multiple fish in a row. If I switch to a different fishing rod by talking to Bloop, will it break my fishing chain?
You're warned right in the shop that changing rods will reset your current chain.
That includes buying a new rod (which automatically equips the bought rod) or switching to one in your inventory. So if you were binging on fishing and you're ready to buy a new rod, you might want to wait until you're about ready to sign off (since the multiplier doesn't persist between plays).