To add to Preston's advice and infomation on using a "throat pump". Never use one on a small (under 12") fish. It is probably best to learn on a dead specimen. I went to a "put and take" lake and harvested a nice rainbow. I dispatched the fish and got out the pump. Depress the bulb and insert the tube into the fish's mouth until you feel the tube stop against the narrow part of the throat. Release the bulb and slowly draw the pump out of the fish. The suction of the bulb being released will draw any recently ingested food items into the tube. Then you squeeze the bulb and empty the contents into a container of some sort to inspect the contents. If you don't want to kill a fish to practice, you could ask another angler who has killed one if you could practice on their fish. Practice makes perfect. The first one that I pumped had some green colored item in it. I squeezed it into my container for examination, that fish had been feeding on lime sherbert sparkle "Power Bait" SS