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Study Documents Prevalence of Fish Disease Using Photos Collected by Public

Research Shows Power of Citizen Scientists in Understanding Aquatic Environments

September 17, 2019

A smartphone is held by two hands, showing the Fish Finder app's opening page.

A Shedd Aquarium research biologist published a new research study that documents the prevalence of a fish disease, black spot disease, across North America using solely photos of fish taken by the public. The study, published in the International Journal for Parasitology: Parasites and Wildlife, helps answer questions about where the disease is most pervasive in the ecosystem for several species of small-bodied native fish. It also establishes that photo databases like iNaturalist are valid resources for data collection and species surveying, as the study is the first to be published using only third-party photos.

“In addition to allowing us to document the prevalence of a disease in freshwater ecosystems across North America, this research study is proof that photo databases populated by anglers, boaters, kayakers, recreational fishers and more can be used for real scientific purposes,” said Dr. Austin Happel, research biologist at Shedd Aquarium and author of the study. “I am optimistic that with continued photo submissions on these databases, scientists can utilize this data to help us learn and answer questions about aquatic animals and their ecosystems.”

To conduct the study, Happel evaluated 1,383 photos of fish submitted to iNaturalist, an online platform that community members can submit photos of nature to, which then creates a catalog of photos for scientists to view where wildlife can be found and can even help flag the spread of invasive species. The photos were submitted from 471 different users across North America; those individuals are referred to as “citizen scientists” by researchers because they are community members volunteering their time to contribute to scientific data collection.

The study concluded that regardless of fish species group, black spot disease is most prevalent in waterbodies in southern Ontario – watersheds of East Georgian Bay, Northern Lake Ontario, the Niagara Peninsula and Northern Lake Erie – with a 27% prevalence of the disease, as compared to the average prevalence across the rest of the study area, 6.8%. Causes for this geographic pattern, the study notes, are likely due to a combination of biological ecological and environmental factors. None of these factors are indicators of poor ecosystem health, however, as diverse parasite communities are thought to occur in healthy ecosystems.

“While this study provides insight into where this disease can be found and what fish it is impacting, the most important aspect of the study is that it shows us research, even parasitology which often receives little funding, can be conducted with the help of citizen scientists,” said Happel. “Data voluntarily provided by community members offers a means of collecting data at frequent internals and across wide geographic areas with a low cost to agencies.”

Just as there is little information known about the black spot disease prior to the new study, there is still much to be studied about aquatic animals in the Great Lakes watershed. Using the iNaturalist platform, Shedd Aquarium created an original app to address gaps in knowledge in the Great Lakes region using photos from citizen scientists. The app, called the Great Lakes Fish Finder App, offers a field guide to Great Lakes fish species and enables users to submit images of fish they catch or see. Knowledgeable community members and Shedd researchers help users identify the fish species which can later be used to inform scientific studies, like the new study published by Happel. The app is available for Apple and Android devices.

To read the open-source research study published in the International Journal for Parasitology: Parasites and Wildlife, visit


Happel, A., A volunteer-populated online database provides evidence for a geographic pattern in symptoms of black spot infections, International Journal for Parasitology: Parasites and Wildlife (2019), doi:

PHOTOS: Photos submitted to the Great Lakes Fish Finder app and other relevant images are available for download: https://personal.filesanywhere... credit: ©Shedd Aquarium