Aug. 29, 2008
Vol. 38, No. 395

For more information, contact Craig Shirey, Fisheries Section, Division of Fish and Wildlife, 302-739-9914, or Joanna Wilson, Public Affairs, 302-739-9902.

Fish Kill Involving Juvenile Menhaden Reported in Torquay Canal

            This morning, DNREC staff responded to a fish kill involving an estimated 5,000 to 10,000 young Atlantic menhaden 4 to 5 inches long in Torquay Canal, a deep circular lagoon upstream from the mouth of Bald Eagle Creek, located at the head of Rehoboth Bay. Testing by the DNREC Division of Water Resources environmental laboratory showed the likely cause: not enough dissolved oxygen in the water.

            “We’ve been expecting fish kills all summer, but the dry conditions and other factors seem to have prevented that so far. This is the first fish kill we’ve had since June,” Fisheries Manager and Fish Kill Coordinator Craig Shirey said.

            Shirey and DNREC Marine Biologist Dr. Robin Tyler, who helps monitor water quality in the area, agree that the weather created ideal conditions for a fish kill in the canal, a still water lagoon with a long history of fish kills due in part to its lack of water-oxygenating circulation.

            “We had a little rain yesterday, with cool, cloudy weather that chilled the surface layer of water. The cooler surface water sank, and mixed with the water underneath. An investigator at the scene noted the smell of hydrogen sulfide, an indication of anoxia – no dissolved oxygen – in the water below. In a very short time, possibly even minutes, the entire mix would have turned anoxic and affected anything in it at the time, in this case, the menhaden,” Tyler explained.

            Young menhaden travel in large, dense schools, and tend to congregate in sluggish waters such as Torquay Canal, to which they are drawn by abundant algae, their primary food source.

This afternoon, water samples from the site were screened by the University of Delaware for any harmful algae that might have contributed to the fish kill. Numbers were well below any concern for toxicity.

To report a suspected fish kill, please call 302-739-9914 from 8 a.m. to 4:30 p.m. Monday through Friday and 800-523-3336 weekends and after hours, and give location and, if possible, an estimated number of fish involved and species if known.