Ayer Creek becomes first Coastal Bays tributary with Pfiesteria confirmed; lesioned menhaden widespread in Chesapeake Bay

August 4, 2000

This is the fourth biweekly report for 2000.

Fish Health and Pfiesteria
Ayer Creek: On July 24, 27% (33 of 122) of menhaden captured during routine sampling of the fish community by Maryland Department of Natural Resources Resource Assessment Service on Ayer Creek (a tributary of Chincoteague Bay) at the Rt. 376 bridge were found to have ulcers (see photo on left).  This is the first time that a significant percentage of menhaden with lesions has been found in the Coastal Bays since the fish health monitoring program began sampling the waters in 1998. No fish kill has been observed this season in the area. Pfiesteria piscicida was identified, however, by Dr. Oldach's genetic probe in water samples collected July 24th from the site but detected in low abundance; water samples sent to Dr. JoAnn Burkholder's showed no evidence of toxicity. Six subsequent visits to the area during the past two weeks has found similar lesion incidences among menhaden and Pfiesteria-like cells at very low levels. To date there is no evidence of toxic Pfiesteria activity. Other fish species found in the net catches appear healthy. Further sampling will be conducted during the week of August 7.

Nanticoke River: A small number of ulcerated menhaden were recorded from two samples collected from the Nanticoke River on July 19. Routine water monitoring results were negative for Pfiesteria in the region at this time. Additional sampling on July 31 in the Nanticoke watershed found fish with lesions, mostly white perch, in Chicone Creek and sampling on August 1 found ulcerated menhaden (8 of 26; 31%) on Wetipquin Creek. Water samples collected at all these sites have been negative for Pfiesteria except for one sample collected at Wetipquin Creek on August 1. Results from North Carolina State University indicate low densities of Pfiesteria-like cells in this sample. This site will be revisited on August 4.

Fishing Bay: Lesioned menhaden were captured at two sites in the Fishing Bay watershed during routine sampling on August 2. Approximately 40% of 500 menhaden captured at Pokata Creek and Elliots Island Rd were found to have lesions. Water samples indicated the presence of Pfiesteria at moderate levels by both Dr. Oldach's probe and North Carolina State University. Moderate levels of an organism which may be Pfiesteria were also identified in samples collected on the western shore of Fishing Bay associated with a low number of lesioned menhaden. The Pokata Creek site will be revisited on August 4th.

Pocomoke River: On the Pocomoke River, no menhaden have been captured during two sampling events since July 13th but other fish species captured appeared healthy. The area is scheduled to be sampled again on August 8th.

Cambridge Creek: A high percentage of lesioned menhaden were collected in Cambridge Creek (a tributary of the Choptank River) on August 3, and gulls were observed feeding on the fish in the area. Water samples were collected for Pfiesteria analysis and results are pending.

Baywide: More than 132,000 fish have been examined during the fish health monitoring program through the Chesapeake and Coastal Bays. Overall percentage of fish observed with anomalies (sores, ulcers, lesions, tumors, etc.) remains below 1% with local summer season events having >1% affected fish described previously in this and earlier reports.

A reminder - please report fish kills, sick fish or fish with lesions to the Maryland Fish Health Hotline at 1-888-584-3110.

Routine Pfiesteria sampling.
Approximately 70 sites in the Chesapeake and Coastal bays are monitored monthly for the presence of Pfiesteria. Ayer Creek became the first coastal Bays monitoring location where Pfiesteria piscicida has been confirmed. In Chesapeake Bay, a positive sample has been identified this week from a routine monitoring sample collected from the Middle River on July 20th. For year 2000, we now have 9 out of approximately 420 water samples positive for Pfiesteria (see map below). None of the samples has tested positive for toxicity yet this year.

Weather, Water Flow and Water Quality
Around the Bay, flow conditions for July continue to follow very normal flow patterns for the Bay. Local rains patterns have produced regions with elevated water flows over historical levels. The USGS monitoring station located on Nassawango Creeek in the Pocomoke Basin in late July - early August for example shows water levels 5-25 times greater than the 49 year historical median levels.

Water quality conditions in Ayer Creek

 and the Nanticoke River

in the areas where fish with anomalies have recently been found show water temperatures tending to be lower this year versus 1998 and 1999. Salinity levels at monitoring sites have been declining in the past month and both conditions would be related to the recent stretch of cloudy and rainy weather.

Continuous water quality monitoring stations are in place through the EMPACT program (Environmental Monitoring for Public Access and Community Teaching) at three sites on the Pocomoke River in the region of the 1997 fish kill; a fourth station is now up and running on the Chicamacomico River where fish health events have been recorded in previous years. River conditions for the Shelltown area during the first half of July show water temperatures heating up to near 30 oC (about 86 Fo); dissolved oxygen levels were slowly declining during mid-July at all three Pocomoke sites (Shelltown, Cedar Hall Wharf and Rehobeth) to levels typically considered stressful for warm water fish (below 5 mg/L). Oxygen conditions upstream of Shelltown have declined to severely low levels (around 3 mg/L) versus the Shelltown station (just below 5 mg/L). This pattern in water quality has been observed since 1997 and may have implications for keeping menhaden and other species of fish in the lower river by reducing access to these upstream areas.

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