When it comes to learning to fish you can spend a lifetime, but if you want to learn the basics of rod and line fishing then Graeme Pullen (he's been an angling journalist for decades) does a show on YouTube called the totally awesome fishing show, goes from basics right up to catching record breaking sharks and him and his son mike are really likeable guys so it's easy to learn from them.
That's a fun hobby and you could catch fish for the table, (carp are very tasty from running water, if you're allowed to take them, check the rules for your piece of river.) do also check whether you need a permit or be a member of a club to fish in your river, it's not always obvious, you'll definitely need a rod license, came from the post office last time I had one, I've only been sea fishing for a few years so I haven't needed one.
If you're planning on learning to fish for survival then you'll want to learn how to make and use fish traps and nets, but you won't be able to practice the use of them in a river though as I think it's prohibited near enough everywhere.
You can still learn the skills though and put them into practice if you need to.
One thing that it really is worth looking into is whether there are American Signal Crayfish in your stretch of water, they're an invasive species that escaped from farms and do untold damage to our rivers, and consequently they need to be got rid of but they're also really tasty, so if they are in your local river then grab yourself a permit (think the environment agency issues them), it's a small fee and they'll want to make sure you can tell an American crayfish from a native. Then grab a couple of folding prawn traps and you'll have a free supply of something that you'd pay a whole bunch of money for!
That is not dead which can eternal lie, and with strange aeons even death may die.
