Special new fish species for cold biomes

In my opinion, each biome should have its own unique set of fish, each with its own rarity, so that players who enjoy fishing would have reasons to venture into other biomes to collect them all. Cold-water fish have developed a natural protection against the cold and would only be found in cold biomes. They would also have their rarity level and chances of being found at specific times or hours, such as: a certain fish would only appear during snowstorms or at night. presenting a challenge and a reward that would be really cool to obtain.