Much to the satisfaction of commercial and recreational fishermen alike, the speckled or spotted seatrout (Cynoscion nebulosus) is abundant throughout the Gulf of Mexico, along the southern Atlantic coast, and into Chesapeake Bay. Seatrout living at or near the northern extent of their range, however, are vulnerable to rapid and sustained drops in water temperature. This can result in winter kills, also known as cold stun mortality.

“Winter kills can impact the population at the regional level,” observes Dr. Willy Reay, manager of our Chesapeake Bay Reserve in Virginia. “Fishery managers who are aware of conditions that may lead to such kills can help these populations rebound by taking actions including reduced catch quotas, emergency season closures, and recommendations for voluntary catch and release among recreational fishermen.”

To help fishery managers address this issue, Reay and his staff are using real-time, NERRS monitoring data to create a pilot cold stun alert system that identifies when water temperatures in the Carolinas and Chesapeake Bay drop to exposure thresholds that can cause mass seatrout die-offs. The system also tracks how long these lower temperatures are sustained over time.

“Winter kills are not infrequent,” says Reay. “Their severity depends on environmental conditions, the characteristics of the water body, and the presence and behavior of the fish.

This winter, our region’s seatrout population experienced a notable winter kill, similar to those that occurred in Virginia and Maryland in 2014, South Carolina in 2011, and in North Carolina between 2010 and 2015.”

The scale of this recent kill prompted North Carolina’s Division of Marine Fisheries to enact an emergency season closure through June 15th to allow surviving seatrout to spawn in the spring. Likewise, South Carolina’s Marine Resources Division asked the public not to target seatrout in its waters. Virginia is continuing to assess population impacts.

“We are working with other reserves to expand the cold-stun tool throughout the Mid-Atlantic, Southeast, and Gulf of Mexico, so it can inform fisheries management decisions like these next year,” says Reay.  “Because the NERRS monitoring program collects data on critically important water quality parameters in real-time, we can be nimble in identifying the onset of environmental issues like this and helping coastal communities and resource managers make informed, time-sensitive decisions.”