Did you go back and consume the Gimberry after you caught the berry fish? It is located up and slightly left of the sell station. If you don't eat it you can't catch the gimfish. After you eat the Gimberry it just takes a ton of bait. Keep at it! You'll get there.
You can, but you need special gear and have to start at some very early hour of the morning in order to avoid problems... so I opted for the hike up to the glacier. Still well worth it.
