Win the Kyushu/Okinawa tourney to gain the ability to see fish you have not caught yet as yellow shadows instead of black ones. It does not highlight every one of them at the same time, but it makes getting to 100% much easier. You will also gain access to the new Area, which contains new fish.
Rare fish will appear as red shadows. The following list includes all of them and what to catch them with.
Kanto Area LOCATION - FISH(FISHING APPARATUS) Oodeo Bay - Red Rockfish (Sea Lice) Guuzenji Lake - Rage Trout (Stone Fly) Koarai Beach - Rainbow Eel (Baby Lonia or Sea Lure worm) Katsumura Bay - Sea Goblin (Broken Ladle)
Chubu Area LOCATION - FISH(FISHING APPARATUS) Hamami Lake - Star Eel (Baby Lonia or Cuttlefish) Nagaha River - Rage Trout (Stone Fly) Manaka Lake - Pink Bass (Stone Fly) Noyama Bay - Midnight Bream (Straw Worm)
Kansai Area LOCATION - FISH(FISHING APPARATUS) Myoujin Straits - Sunrise Fish (Spoon Worm) Godanheki Cave - Giant school of red fish (Sea Lure worm) Hiwa Lake - Pink Bass (Stone Fly) Chamo River - Rage Trout (Stone Fly)
Chugoku Area LOCATION - FISH(FISHING APPARATUS) Shikane beach - Fat Sea Bass (Cuttlefish) Ootori Coast - Round Amberjack (Palolo Worm or Sea Lure S fish) Isono Island - Midnight Bream (Palolo Worm, Straw Worm, or Prawn) Fukuyobi Water - Devil Puffer (Possum Shrimp)
Shikoku Area LOCATION - FISH(FISHING APPARATUS) Urayama Dam - Rage Trout (Stone Fly) Kosa Bay - Red Fish, Dragon Bonito (Prawn) Summer/Sunfish (Jellyfish) Summer (rare); Sunfish rare but not Red Fish. Mikoto Bay - Puffer Trio (Baby Lonia) Muwakai Offshore - Round Amberjack (Sea Lure worm)
Kyushu/Okinawa Area LOCATION - FISH(FISHING APPARATUS) Nagasaki Water - Mom In Law (Prawn) Ookita Bay - Eye Rock Fish (Shore Crab); Winter - Ookita Horse Mackerel (Straw worm) Hazakurajima Beach - Jumbo Parrotfish (Ghost Shrimp) Chura ocean - Stone Puffer (Sea Lice)
Tohoku Area LOCATION - FISH(FISHING APPARATUS) Matsurgahara lake - Rage Trout (Doughball) Monaka River - Manface Fish (Doughball or Frog) Annri River - Water Imp (Cucumber) Daimon Strait - Bluefin Tuna (Sea Lure worm)
Hokkaido Area LOCATION - FISH(FISHING APPARATUS) Ishihari River - Chum Salmon (Meal Worm) Marimo Cape - Fat Sea Bass (Prawn) Yakan Lake - Huchen (Fresh Lure Worm or Meal Worm) Oohokku Ocean - Halibut (Sea Minnow)
Unknown Area LOCATION - FISH(FISHING APPARATUS) Rapuso Monument - Pirarucu (Freshwater set) Blue Cave - Red Metal (Bolt) Deppari Cape - Devil Shark (Raw meat) Fish City - Whale Shark (Spear lure)