I was playing a modpack that has this mod in it and was trying to catch every fish and get every rod. But when I was trying to get the soul salmon, I realized that it was taking way too long. So I went into a creative world with only this mod installed to look into this further and I tested every biome specific fish/crate. I found that all of the biome, weather, and moon phase specific overworld fish and crates are obtainable, but all of the nether biome specific fish and crates aren't. You can get all of the generic nether fish and crates, but it's pretty disappointing that a lot of stuff is currently unobtainable...