Lower Susquehanna Fish Kills Believed to be Result of Spawning Stress

HARRISBURG - Recently reported fish kills on the lower Susquehanna River are believed to have been caused by spawning-related stress, according to Pennsylvania Fish and Boat Commission biologists.

“Spawning requires a lot of energy and is very stressful on fish,” said Dave Miko, chief of the Commission’s Fish Management Division. “When a fish is stressed it is more susceptible to infection from a variety of bacteria and viruses. The rigors of spawning may result in abrasions to snouts, tails and fins during courting, nest preparation and defense. These open sores can become infected and may lead to death.”

The Commission has recently received several reports of fish kills occurring in the lower Susquehanna River, ranging from individual fish to groups of several dozen fish of multiple species. The most common species reported have been adult, spawning-aged carp, catfish and smallmouth bass.

In fish kill investigations, dying but not yet dead fish are the most valuable when trying to determine a cause of death. This is because there are numerous common pathogens that rapidly colonize in a dead fish, making it very difficult to determine the cause of death.

“Users of the resource often provide the Commission with the first indication that something is occurring along waterways,” said Miko. “That’s why we’re asking anglers who see dead or dying fish to report them by using a telephone hotline number that has been set up to accept these reports or to report them through our website. If we can get some of the dying fish, our fish pathologists can then examine them for parasites, bacteria and viruses.”

The Commission along with the Pennsylvania Department of Environmental Protection and the U.S. Geologic Survey are expanding their efforts in 2009 to investigate the potential causes of the fish kills and disease which have occurred on young smallmouth bass in recent years.