Understanding Blotchy Bass Syndrome

Coordinated efforts are needed to understand where and when fish and wildlife diseases occur as well as the biological threats that diseases pose to animal populations. However, the ability of resource managers to sample for diseases is usually limited in space and time and requires special training beyond typical skill sets. 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 clinical disease presentation by citizens and community members thus could be an additional resource to expand biosurveillance efforts by fish and wildlife agencies.

Blotchy Bass Syndrome

Black basses (Micropterus spp.) are among the most popular sport fishes in the world and serve as keystone predators within aquatic ecosystems. Melanosis (aka Blotchy Bass Syndrome or BBS) is a condition characterized by black, ink-like spots, on the skin, fins and/or mouths of black basses. For many years, fisheries biologists thought it was just a stress response. Turns out, we were only half right. Researchers at the U.S. Geological Survey (USGS) Eastern Ecological Science Center in Leetown, West Virginia have recently identified that BBS is associated with a novel family of viruses known as Adomavirus (Adomaviridae). 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 (i.e., temperature, spawning, sun exposure). 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.

Black basses exhibiting hyperpigmentation have been observed in numerous waterbodies across the country in increasing frequency. We have received reports of bass with blotchy bass syndrome from major reservoirs, large and small streams, and public and private ponds. Although multiple states have noticed bass with hyperpigmentation, little is known about the occurrence and prevalence of blotchy bass syndrome across North America and no comprehensive surveys have been completed. A coordinated biosurveillance network is needed to understand the geographical extent, seasonality, prevalence, 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 at West Virginia University. However, more help is needed to establish biosurveillance efforts across the fishes’ entire range and sample throughout the year.

Citizen science: Partnering for success

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 encouraging them to share what they’ve seen when fishing likely requires some non-traditional approaches. 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.”

To encourage reports at a broader scale that would be 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, which resulted in over 1,000 angler photo submissions in 2022. 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 MyCatch app of every bass they catch from March 1, 2023 through February 29, 2024 –  whether blotchy or not– to help researchers understand not only where the virus has been observed but also where it has not yet appeared.

Next steps

USGS and partners will be analyzing photos submitted by citizen scientists over the next year to check for new hotspots and identify additional areas to sample to confirm the presence of the virus. State agency and private/commercial fisheries management biologists, who are willing to participate, will receive sample kits to collect tissue samples from blotchy bass they catch. Additionally, 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 more comprehensive “boots on the ground” sampling and engagement efforts with partners at state agencies and volunteer anglers on the ground. “We want to encourage additional reports this year 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. Gaining a better understanding of the various factors that impact virus spread will further enhance detection efforts and inform management practices to stop or slow the spread. Ultimately, coordinated biosurveillance and monitoring should help detect novel viruses before they become established, allowing for appropriate management action.