Fish Health investigations in progress in
Chesapeake Bay, no evidence of toxic Pfiesteria being found|
August 21, 2001
This is the fifth report of the 2001 season.
Fish Health and Pfiesteria monitoring.
On August 7th, 50% (7 of 14) routine monitoring water samples
tested positive for Pfiesteria with the genetic probe by Dr. David
Oldach’s laboratory at University of Maryland Biotechnology Institute. Five menhaden captured in
the region appeared healthy. This is the same region where on July 16th,
9 of 14 samples tested positive for the presence of Pfiesteria. This region was the scene of a prolonged fish
lesion event and numerous water samples that were positive for P.
piscicida presence during August
and September 1999, although there was no evidence of active toxicity.
Back Creek, Manokin
River, area of Millard Long Road bridge:
There were 15 of
27 (55.6%) menhaden collected during routine monitoring on August 9th
that had ulcers. The area was resampled on August 15th and
52.1% (241 of 463) of the menhaden collected again showed ulcers. The
area was revisited on August 20th and approximately 17% (71 of
420) of the menhaden continued to show ulcers although the percentage has
declined relative to the last two weeks.
Each of the two water samples collected each day tested positive
for Pfiesteria but light microscopy results indicated low levels of
Colgate Creek, Patapsco
River: Evidence of a fish kill and fish under stress were
observed on Colgate Creek on August 6th and was investigated by
Maryland Department of the Environment.
Extremely high dissolved oxygen conditions associated with algal
bloom conditions were measured at the site and water samples tested for
nutrient conditions showed high concentrations of ammonia. High ammonia
concentrations can be stressful or toxic to fish.
Water samples collected on August 6th also show one of
three testing positive for Pfiesteria, however, presumptive
counts for Pfiesteria-like cells under light microscopy were
recorded at low densities. Follow-up
sampling on August 9th and 15th revealed no further
fish health problems, but three of six water samples were positive for the
presence of Pfiesteria at low levels.
There has been no evidence of toxicity in one of these samples
subjected to a fish bioassay at Dr. JoAnn Burkholder’s laboratory at
North Carolina State University
Marumsco Creek, Pocomoke
River: A fish kill report was investigated on August 16th
where a total of approximately 16,000 menhaden were found dead. The kill
was estimated to have occurred two days earlier based on the state of
decomposition of the fish. None of the fish appeared to have ulcers and
low oxygen conditions were found at the investigation site (1.3 mg O2/L
at one site and 2.8 mg O2/L at a second site; at least 5 mg O2/L
is typically associated with healthy water quality conditions for most
fish). A sample of seven white perch and four killifish netted at the site
looked healthy. No Pfiesteria was present in water samples tested
with the genetic probe at Dr. Oldach’s lab, University of Maryland
Overall results from the genetic testing of water
samples for Pfiesteria.
notes on water quality condition.
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).
A reminder - please report fish kills, sick fish or fish with lesions to the Maryland Fish Health Hotline at 1-888-584-3110.
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