WPU Biology Students Study Migration of Contaminated Fish in Crabtree Creek

November 29, 2021

Catfish contaminated by PCBs are heading downstream, which may be putting Raleigh residents at risk. And WPU biology students are figuring out why.

PCBs are artificial organic chemicals used in manufacturing until they were banned in 1979. WPU’s biology students have been studying the PCB contamination of Raleigh’s Crabtree Creek in Raleigh for several years, explained Professor Patrick Myer. 

In previous studies, Myer and his students had established that fish in the creek possess high levels of PCBs throughout their muscles and organs. As a result, eating contaminated fish leads to high rates of cancer. 

Myer said the initial contamination site was a small headwater stream near Crabtree Lake. In that area, signs warn that people should not eat the fish due to the health risks. However, about 10 miles down from the contamination site, the signs change to a recommendation of limited but acceptable ingestion of fish.

Myer said Crabtree Creek’s regular flooding might be pushing the highly contaminated fish downstream — to the area where people may be fishing and consuming those fish. 

“A limited study our students did several years back proved this,” he said. “We tagged about 50 catfish near the original spill site and discovered that two of the fish had made it 22 miles down the creek to the Neuse River. Therefore, fish with high levels of PCBs from upstream were being pushed down the creek by frequent flooding and channelization.”

Immersive Learning

Tagging and measuring catfish is just one of two projects undergraduate students are doing this year in Myer’s classes. Getting into the field is part of WPU’s core tenant to provide immersive learning, which means learning by doing — often outside the classroom. 

Myer said this year’s students are performing two research projects, work that includes project development, data collection, processing and analysis, and preparation of a PowerPoint presentation to be given in the spring.

Studying Catfish

This year’s study expands on previous research, Myer said. Students are trying to determine the catfish movements. On a recent Friday, they went to the halfway point at Crabtree Creek to tag and measure the fish. 

“We are particularly interested in what proportion of catfish can withstand the heavy flooding and stay within a particular area,” Myer said. “We are also interested in how fish are affected by natural and man-made ‘fish blocks’ in the creek, which do not allow fish to swim back upstream.” 

In some cases, fish manage to get past the fish blocks, Myer said. For example, Lassiter Mill waterfalls is a good example of a natural fish block. As a side project, the students release some of the tagged fish above the falls to see what conditions push them downstream.

“Will the fish voluntarily swim over the falls, or does the flooding push them over?” he said. 

Students who partake in this work must first catch the fish in traps. The traps then soak for two days before they measure, weigh, and tag each fish. They catch far more than they need, ranging from a few ounces to 5 pounds each. Students release most of the fish and then keep some to release at Lassiter Mill falls. 

Robert Davis, a senior, said he was surprised by the number of catfish they found as well as how they varied in size. 

“It was a lot of fun working with Dr. Myer and Dr. [Lisa] Bonner,” Davis said. “It was such a great opportunity to step outside of the classroom and participate in fieldwork firsthand. It was fascinating to see the variety of animals present even in such an urban setting. We noted these through both trail camera footage and underwater traps.” 

Myer said he’s proud that WPU offers undergraduate research that encompasses a wide variety of projects in the biological sciences. 

“Student research is a valuable tool for skill development in preparation for both jobs and graduate/professional schools,” he said.

Habitat Study

The second project is a study of habitat use by mammals and birds at Crabtree Creek. Each student set up and is monitoring trap cameras at strategic localities along the creek shoreline. Students check the camera’s recordings each week and note the species and numbers. 

The goal is to identify the species and numbers of mammals and birds that commonly use the area to access the creek. Myer said it’s a habitat bottleneck along the greenway, with wading birds, ducks, geese, many deer, squirrels, raccoons, muskrats, groundhogs, rabbits, various rodent species, and beavers all gathering. 

The goal is to see if the frequent flooding impacts their use of the area. 

“The results so far have been absolutely remarkable,” Myer said. “We have already discovered that heavy flooding does not hamper the return of many of these animals. After a recent heavy flood, where the water went from 2.5 to 16 feet deep, many of our recognizable individual birds and mammals immediately returned after the water subsided, including the beavers. So far, this has been a very successful data collection season.” 

The students involved this semester are Robert Davis (senior), Cassidy Maitland (junior), Logan Blackmon (junior), Dallas Russell (senior), and Leilani Nguyen (senior).