How to Check Fish Populations in Ponds

Checking the fish population in an outdoor pond can be a difficult task. Fish don't tend to spend a lot of time at the surface and remain still while a concerned pond owner does a headcount. Following a few easy steps can greatly increase your chances of getting an estimation as to how many fish are inhabiting your pond, if your pond contains larger fish that are identifiable in photographs.

Things You'll Need

  • Incandescent flashlight
  • Fish food
  • Submersible lighting (optional)
  • Digital camera
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Instructions

    • 1

      Avoid attempting to check your fish populations during the day as most species of goldfish and koi, as well as minnows, will remain beneath the surface in the heat of the day. Do a head count after dark, on a cool evening. If it has recently rained this can also help bring the fish to the surface. Stay away from the pond during the day when you plan to do a head count at night.

    • 2

      Skip feeding the fish in the pond for one day. Hungry fish tend to surface for food. Allow the pond to settle and the inhabitants to feel comfortable enough to emerge from their hiding places.

    • 3

      Take an incandescent flashlight to your pond at night. Go to your usual feeding spot and place your submersible lights into the pond, if you have them. Submerge the lights gently to avoid disturbing the fish. Begin sprinkling the fish food on the pond surface.

    • 4

      Photograph the scene using the night mode of your camera, whenever there is a group of two or more fish at the feeding spot. Continue doing so as you continue sprinkling more food onto the water. Feed the fish at a rate that is consistent with how quickly they are consuming the food. Continue photographing until you are confident you have had at least one visit from every fish in your pond.

    • 5

      Return to your house. Eliminate duplicate photographs and images that are too blurry. Once you have a good pool of photographs, begin counting the peak numbers you see in each photo. When you see several photos with the same general number of fish, this is likely close to the total number of fish that visited your feeding.

    • 6

      Repeat this process every other night for a few nights, gathering a sample of three or four feedings with photographs. Identify the peak number you saw in any photograph and use that to form an estimation on what kind of population you may have. Determine the difference between the fewest fish you captured in a photo, and the most. Add this number to your peak number to arrive at an estimate.