I'm no good at catching fish one at a time, but I grew up on a commercial fishing boat. Here's a couple of fish traps- the first one is good for streams- using closely-spaced poles can substitute for a net as a way to get fish to congregate for a short while and increase your catch with rod and reel or a spear. You can also net off streams if you've got a net and take everything and the poles can be stacked nearby when not in use. You can't leave it too long, as any trash or branches can screw it all up as they come downstream.
For saltwater, I used to help tend a sardine weir in downeast Maine, too, when I was in college. This is a permanent shoreline trap requiring an investment in time and 3-4 people with a good boat and access to nets. They trap fish and then you periodically corral the fish and heave them out of the water. An adult and a kid can tend and maintain the weir, but you need 4 strong people to build it and hang the nets initially. Looks more intimidating than it is. The picture shows a big ass one that provided about 10% of the US's canned sardines in the 50's and 60's. A manageable weir is 5,000-7,000 sq feet.
Depending on where someone is, a serviceable crab trap, or crayfish trap if in fresh water, can be made from a 5 gallon bucket with a lid if you can bury it to where the lip is only 1-2 inches above the gravel. The hole in the lid needs to be only 2-3 times the body size of whatever you're looking to catch. You poke 1-2 small holes an inch or two above the bottom, insert string with a slipknot at the end (to hold bait), put the lid on and bury it.
Paul B. (Hawsepiper)
Thanks, Paul. I appreciate you taking the time to teach us this - I learned something new too.