In 2024, 1,865 volunteers reviewed underwater videos; cameras recorded 4 fish species missed by traditional traps

Usually, in a fish survey, researchers place nets or traps into the water to catch fish, allowing them to count and identify the species collected. However, not every fish would swim into the net, and some fish could escape the traps, leading to incomplete survey results.

In 2024, researchers decided to use a different method. They paired traditional fish trapping with underwater cameras and invited volunteers to examine the footage. The effort involved 1,865 citizen scientists, who reviewed and analyzed the video footage which consisted of many short video fragments and helped to find fish in waters. This was the Where's Walleye? project, which found that four fish species, golden shiner, common carp, black crappie, and smallmouth bass, were detected on camera but not in traditional trap surveys, showing how underwater video can reveal animals that standard sampling methods may overlook.

Why traditional fish surveys miss some species


For decades, fish surveys have relied on nets, traps and other sampling equipment to estimate fish populations. Researchers can investigate fish directly and gather data like size, weight, and condition of the fish. However, they also have limitations. Fish may avoid entering traps, escape before they are counted or simply move through areas where sampling equipment is not placed. As a result, some species can remain undetected even when they are present. Underwater cameras have also been studied as a way to observe underwater life. Rather than waiting for fish to go into a trap, the cameras capture the underwater activity that occurs in front of the camera, making a continuous visual record of the activity.

How citizen scientists joined the fish hunt

Watching hours of underwater footage is a task that would take researchers enormous amounts of time. Researchers launched the Where's Walleye? citizen science project, where participants watched short underwater video clips and recorded whether they could see fish. They also identified different species whenever possible. Many volunteers reviewed each video, which meant that researchers could test the different volunteers' responses for consistency and enhance confidence in the final classifications.

What the cameras revealed beneath the surface

The underwater video was more than a confirmation of what researchers already knew. It also identified species not detected by the traditional trapping method. This showed that using one survey technique alone can miss a proportion of the fish community of the same waterbody. The cameras also recorded fish behaving naturally in their habitat instead of reacting to traps or handling by researchers. This gave researchers an additional tool to study fish behaviour, including the time they spent and how they moved throughout the water. The results indicated that underwater video could supplement existing approaches by filling gaps in traditional surveys.

Why one survey method is not enough

Traps can be used to obtain useful biological data as individual fish can be measured. However, cameras provide a non-invasive alternative to observing species which might not be captured. It is particularly crucial for conservation projects to have more accurate information when monitoring rare and declining species. The loss of even a small number of species during regular surveys can influence management decisions and habitat assessments.

How underwater cameras changed fish surveys

The success of the project indicates that underwater imaging could become more significant in freshwater studies. As cameras become less expensive and easier to use, scientists can observe rivers, lakes, and wetlands more often without interfering with the wildlife. In addition, video recordings will provide researchers with a permanent archive that can be accessed with the latest methodologies of identification. Instead of depending only on notes obtained from one field study, researchers can analyze old videos for more information about various species and how fish communities change over time.