Switch Ginger Island freshwater only yielding ocean fish

[RhysStardew]

Trying to complete the island fishing quest, and when it came to catching blue discuss, the river and pond on ginger island west are only yielding tuna, super cucumber, and lionfish. These are all ocean fish and shouldn't even be able to spawn in these areas.

 

[olivia11]

Trying to complete the island fishing quest, and when it came to catching blue discuss, the river and pond on ginger island west are only yielding tuna, super cucumber, and lionfish. These are all ocean fish and shouldn't even be able to spawn in these areas.

That definitely sounds like a bug those fish should not be spawning there.
You might want to try reloading the save or checking for mods that could affect spawns.