Talk to your host and ask if there is anything in particular you need to bring, if fishing gear is provided for you, what you’ll do, where you’ll stay, what you can do in your free time, what’s the fishing like, how you can go fishing etc.
Get your travel insurance.
Check for visa/vaccination requirements. Stay up to date with the latest travel advice and restrictions for your destination.
Get a local sim card on arrival.
Make sure to have a backup plan in case your plans change.