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October 21, 2022

Observations of fish and wildlife disease by the public can supplement biosurveillance efforts by state and federal agencies. Researchers at the U.S. Geological Survey Eastern Ecological Science Center are working with partners at universities, state agencies, and recreational organizations to crowd-source smartphone images from anglers of fishes exhibiting blotchy bass syndrome.

Coordinated efforts are needed to understand where and when fish and wildlife diseases occur and the biological threats that diseases pose to animal populations. However, resource managers’ ability to sample for diseases is usually limited in space and time. The public is often aware of and interested in fish and wildlife diseases, particularly those that lead to changes in appearance of animals or affect species of high recreational or commercial value. Observations of disease by citizens and community members thus could be an additional resource to expand biosurveillance efforts by fish and wildlife agencies.

a USGS scientist wearing a black t-shirt and a facemask is swabbing the skin of a fish to collect a biological sample
Clay Raines, a USGS scientist, performing a dermal swab on a Largemouth Bass at a Bass Pro Shops retail store with a presumptive case of blotchy bass syndrome.  The collected swabs can be used to isolate DNA and RNA which can be used to identify pathogens including those associated with hyperpigmentation.  The study of blotchy bass syndrome is part of an ongoing EESC biosurveillance effort to study viruses in wild fish.  


Black basses (Micropterus spp) are enigmatic North American fishes that support the most economically valuable freshwater sport fishery in the United States and serve as keystone predators within aquatic ecosystems. Hyperpigmentation or black, ink-like spots, on the skin of black basses has been observed in a number of waterbodies across the country in increasing frequency.

Researchers at the U.S. Geological Survey (USGS) Eastern Ecological Science Center have recently identified that this condition, now called blotchy bass syndrome, is associated with new, emerging adomavirus. Association of viruses and skin hyperpigmentation had been documented before in humans, but never in fish. Basses with skin hyperpigmentation were first observed in the 1980s and at the time it was assumed that the condition was caused by environmental contaminants or stressors. The potential for virus-caused hyperpigmentation poses a more complicated fish health diagnosis because while an adomavirus has been identified as the culprit, other factors like contaminants or stressors may still play a role in when and where blotchy bass syndrome occurs.

Although multiple states have noticed bass with hyperpigmentation, little is known about the prevalence of blotchy bass syndrome across North American and no comprehensive survey has been completed. A coordinated biosurveillance network is needed to understand the geographical extent, seasonality, and biological threat of this viral disease to black basses.

In early 2021, USGS Eastern Ecological Science Center established a blotchy bass syndrome task force that includes federal and state fisheries managers across the states where black basses are managed. “Often wildlife disease research is reactive, for example, responding when you observe a die off of fish. In this case we can collect baseline information in real time, with the goal of being able to use these data to build predictive models and potentially forecast where and when we might see blotchy bass next,” notes Clay Raines, a USGS biological science technician with Eastern Ecological Science Center who is helping investigate blotchy bass syndrome as part of his dissertation research. However, more help is needed to establish biosurveillance efforts across the fishes’ entire range and sample throughout the year.

Gloved hands and a discolored swab showing successful collection of hyperpigmented skin tissue to the swab.
A dermal swab being used on a Largemouth Bass at a Bass Pro Shops retail store with a presumptive case of blotchy bass syndrome.   We can see the transfer of pigmented epidermal tissue to the swab changing its color. The collected swabs can be used to isolate DNA and RNA which can be used to identify pathogens including those associated with hyperpigmentation.  The study of blotchy bass syndrome is part of an ongoing EESC biosurveillance effort to study viruses in wild fish. 


Recreational fishing is a popular pastime in the United States, with over 40 million people fishing for freshwater species every year. Blotchy bass syndrome has received increased attention from anglers and resource managers during the past decade and is a frequent topic of discussion and reporting on angling websites and blogging platforms. “Although bass with spots have been observed for decades, we are now seeing fish with this condition in new places and new waterbodies where people have not noticed splotchy fish before,” says Raines.

Anglers thus have the potential to contribute to biosurveillance efforts by reporting the condition of the bass they catch to researchers – but how to encourage them to share what they’ve seen when fishing? Researchers turned to social media to solicit images of bass with black spots from anglers. Smartphone images and associated metadata such as the location and date of the photo represent a unique opportunity to gather substantial information about blotchy bass syndrome with minimal time, effort, and resources on behalf of the angler or agency. A citizen science approach fosters public engagement in natural resource management and can boost science literacy, helping ensure that management and policies are socially accepted. Soliciting citizen science participation among the public can also lead to increased ownership over fisheries management and exercising this “social license” has extended benefits to both agencies and communities.

“Nearly everyone has a smartphone and could be contributing to the dataset– that’s up to 300 million potential citizen scientists in the United States!” says Raines. “Even 10 years ago, if you wanted to be a citizen scientist you might need to attend a weekend workshop to get certified to collect data for one specific research project. Now citizen science can be much more inclusive and there are lower barriers to participating. For our project, participants don’t need a formal training course because what we need in a photo is captured by how people naturally take pictures of fish.”

USGS and partners at West Virginia University first requested public reports about blotchy bass via grassroots campaigns on social media that targeted special interest groups such as the North American Native Fishes Association. However, these initial efforts resulted in only modest gains of information from anglers. To encourage reports at a broader scale that would be more useful for understanding where and when blotchy bass syndrome is occurring, researchers took a two-pronged approach. First, they leveraged messaging through larger social media channels hosted by state agency partners such as Texas Parks and Wildlife Department. Anglers who witness suspected cases of blotchy bass syndrome in Texas can send them directly to an agency biologist through the end of December 2021. In a second, complementary effort, researchers established new partnerships with Bass Pro Shops and Angler’s Atlas.  Both of these recreational organizations are well-known, trusted resources of anglers nationwide, which helped increase the reach of the request to anglers to submit images of their catches to benefit the national biosurveillance network. Anglers are encouraged to submit photos to Angler’s Atlas of every bass they catch through November 2021–  whether blotchy or not– to help researchers understand not only where the virus has been observed but also where it has not yet appeared.


USGS and partners will be analyzing photos submitted by citizen scientists over the next several months to check for new hotspots and identify additional areas to sample to confirm the presence of the virus. Researchers also have a wealth of information from smartphone images to use to build models which identify what factors are associated with blotchiness, such as time in season, size and type of waterbody, size of fish, and time of day.

The analysis and models will be used to inform where the team should expand sampling and engagement efforts with partners at state agencies and anglers on the ground. “We want to encourage additional reports in 2023 because there’s already evidence that season and temperature may affect blotchy bass syndrome and we want to learn more about why this occurs,” notes Raines. Researchers are already planning another call to citizen scientists for bass photos next spring and summer to help fill in the gaps. Gaining a better understanding of the various factors that impact virus spread will further enhance detection efforts. Ultimately, coordinated biosurveillance and monitoring should help detect novel viruses before they become established, allowing for appropriate management action.

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