Fish Health events continue in Chesapeake and Coastal Bays tributaries, no evidence of toxic Pfiesteria.

September 6, 2001

This is the sixth report of the 2001 season.

Fish Health and Pfiesteria monitoring.
Back Creek
:  Investigations continue at Back Creek off the Manokin River in the vicinity of Millard Long Road bridge. On August 23rd, 25% of the 175 menhaden collected from 4 sites had ulcers. Four water samples were collected at the locations in the area with two of the four samples testing positive for Pfiesteria. Fish health data from August 9th through August 23rd shows the of % of menhaden collected with ulcers during each visit to the Millard Long Bridge site (Figure 1). Between August 9 and August 30th, 9 of 14 water samples collected on Back Creek have tested positive for the presence of Pfiesteria in this area although always at low densities and no evidence of active toxicity.

a bar graph showing time series for % Menhaden with ulcers collected at Millard Long Road Bridge, Back Creek 2001

Manokin River:  On August 30th, MD DNR field crews reported gulls actively feeding on dead and dying menhaden in an approximately 100 yd stretch of river downstream of the confluence of Kings Creek.  There were 20 - 30 moribund fish observed coming to the surface on their sides and 5 dead fish.  All observed fish had anal ulcers.  Dissolved oxygen ranged from 4.6 - 5.7 mg/l.  Two suites of water samples were collected for Pfiesteria analysis.  Results were negative for the presence of Pfiesteria piscicida and P. shumwayae.

Field crews and Natural Resources Police monitored the river between August 31st and September 4th. Very few menhaden have been found but approximately 90% exhibited ulcers. All Pfiesteria tests to date have been negative.

Wicomico River: Field crews and Natural Resources Police monitored the river between August 31st and September 4th. Three menhaden were captured during sampling on September 4th in the vicinity of Whitehaven (1 of 1 menhaden collected had ulcers) and off the mouth of Shiles Creek (1 of 2 menhaden had ulcers). Water samples were collected at each site for Pfiesteria testing. Previously, on Thursday, August 30th, MD DNR field crews observed thousands of gulls actively feeding on dead or dying menhaden between Whitehaven and Mt. Vernon on the Wicomico River. DNR personnel were able to find two menhaden floating on the surface at Whitehaven, both had anal ulcers.  Dissolved oxygen ranged from 5.6 - 7.2 mg/l.  Four suites of water samples were collected for Pfiesteria analysis on the mainstem of the Wicomico from Whitehaven to near the mouth of the river (Marker 18), and one sample in Shiles Creek.  Twenty-eight fish of a variety of species not including menhaden were collected in the area and appeared healthy. All Pfiesteria tests to date have been negative.

Colgate Creek, Patapsco River:  Investigations continue since the August 6th fish kill. Maryland Department of the Environment and Maryland DNR continue to monitor Colgate Creek in Baltimore City. There have been eight positive results for Pfiesteria from fifteen samples taken over the last three weeks.  No recent evidence of toxicity has been found. Elevated ammonia levels remain a possible cause for the fish health event.

Beardís Creek: On August 28th, approximately 900 dead menhaden were report in Beards Creek, a tributary of the South River (Anne Arundel Co.).  Most of the dead fish were in a small, shallow, unnamed tributary where they probably died due to low diurnal oxygen levels.  Afternoon dissolved oxygen levels were very high (9.3-11.2 mg/L) suggesting that they may have reached lethal levels early in the morning. A bloom of Gyrodinium estuariale was in progress.  A water sample was collected for Pfiesteria testing. Sample results are pending.

Nanticoke RiverOn August 20th, 24% of menhaden (16 of 68) collected upstream of Wetipquin Creek had ulcers. This routine monitoring site has been sampled five times this year and no Pfiesteria has been found in the area.

Coastal Bays canal near West Ocean City:  On August 29th, approximately 3,000,000 dead Atlantic silversides were reported from a canal in West Ocean City (Worcester Co.).  Investigation by DNR Fisheries Service personnel on the morning of August 30th revealed that a sill of sand and silt had built up near the mouth of the canal, stranding fish inside except during high tides.  Dissolved oxygen was very low in the canal: 2.1 mg O2/l at the surface, 0.25 mg O2/l  at one foot, and 0.05 mg O2/l at two feet (bottom) and is the probably cause of the kill.

Overall results from the genetic testing of water samples for Pfiesteria.

As of August 31st, 10% (47 of 459) of routine water samples collected for 2001 were positive for the presence of Pfiesteria.

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

General notes on water quality condition.
Flow conditions for the Chesapeake Bay have been below average since May and with the exception of April, flows into the Bay are below average for the year. Since August 15th, conditions at Nassawango Creek, Snow Hill, MD on the Pocomoke River however are 3-5 times the median discharge levels for the 51-year data set for the area.

Salinities have declined in recent days in response to the increased flows as can be seen at the continuous monitoring stations at Rehobeth on the Pocomoke River, Drawbridge at the Chicamacomico and Decoursey Bridge on the Transquaking River (see charts below).

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