Using a throat pump to acquire a sample of what a fish has recently been feeding on is not an irresponsible or inhumane act. A proper throat pump has a beveled end that tapers down slightly to avoid any harm done on fish, and the fish itself does not have to leave the water for more than three seconds to grab a throat sample. A throat pump is not meant to be jammed into the stomach of the fish, only pull a sample of what has recently been ingested.
To throat pump a fish, cradle it upside down in your net with the pump in your opposite hand. Fill the bulb with water, then allow most of it to be squeezed out while the tube remains wet. Depress the bulb, insert it directly into the fish’s throat and quickly release the bulb. Immediately set the fish back in the water and set your throat pump aside. Release the fish before examining the contents.
Once the fish has made its way safely back to the depths, squeeze the contents from the pump into a small glass vial with some fresh water. This will be a great indication of exactly what fish are feeding on in recent minutes, pay close attention to the bugs that are still alive and moving. From here, choose your fly accordingly to match what is on the menu.