Inside N.C. Science: DNA markers track fish migration

On a cloudy spring day last year, I had the opportunity to go out on the Roanoke River with biologists from the North Carolina Wildlife Resources Commission. I collected fish with them as part of my job as a geneticist at the N.C. Museum of Natural Sciences. We work in conjunction with NCWRC and use genetics to track and manage stocking programs for American shad, a native fish currently in decline.

In an effort to bring American shad back to traditional population numbers, NCWRC goes out on the Roanoke and Neuse rivers every spring to collect adult American shad returning to spawn. These fish are taken to hatcheries to spawn; eggs are allowed to hatch safely without being eaten by the predators that share their river ecosystem. The baby fish, called fry, are then released back into the river. In the fall, NCWRC goes back onto the rivers to see how many juvenile fish they can find.

And here is where my job comes into play. NCWRC sends us small fin clips from all adults and juveniles. At the museum, we extract DNA from this fin clip. We then create a unique genetic profile for each fish, using 12 microsatellite markers. Microsatellites are short, repeating stretches of DNA. For example, one string of DNA may contain a certain sequence that repeats anywhere between 10 and 30 times. Such a marker would consequently have 21 different forms, which are called alleles. These microsatellites are scattered throughout the genome in everything from bacteria to humans and, because of their variability, are powerful tools for genetic analysis.

Once we have a unique genetic profile created for each fish, we can use that data to gather a lot of information. We can tell how many of the juveniles NCWRC caught were fry released from the hatchery – versus fry produced in the wild. We can tell if certain stocking locations have greater survivability rates than others. We can tell if and how many of the adults they caught in the spring were actually produced at the hatchery and have returned to reproduce. We can tell if returning adults spawn in their birth river or migrate between rivers. We can even tell if a species has genetically distinct populations between river systems.

NCWRC uses all this information to make informed decisions on how best to stock the rivers and ensure we have great fishing in North Carolina for years to come.

This story was originally published November 1, 2015 at 1:30 AM with the headline "Inside N.C. Science: DNA markers track fish migration."