Localized fish health events in Chesapeake and Coastal Bays
August 23, 2000
This is the fifth biweekly report for 2000.
Localized fish health events are being observed over areas of the lower Eastern Shore in the Chesapeake and Coastal Bays, and recently at several sites on the western shore of Chesapeake Bay, primarily in waters with measurable salinity. Most fish collected representing a wide range of species have appeared healthy and the recent events are mainly related to menhaden. A detailed summary of river systems under heightened investigation due to fish health events and being monitored for fish health, water quality and Pfiesteria testing is given below.
Fish Health and Pfiesteria
Marshall Creek, Newport Bay watershed: On August 7th, 16 of 41 of menhaden collected had external ulcers. Additional sampling on August 10th, 14th and 17th found 23 of 146, 0 of 23, and 25 of 36 menhaden with ulcers respectively. Pfiesteria piscicida was identified from water samples at the site August 7th and 10th with no evidence of toxicity based on field observations. No Pfiesteria was found in water samples from August 14th and 17th .
Pokata Creek at Fishing Bay: On Pokata Creek, Sampling on five days between August 4th and 15th only collected menhaden on August 4th (1 of 2 menhaden had ulcers) and August 15th (14 of 28 menhaden with ulcers). All other species looked healthy. Water samples tested positive for Pfiesteria at the same sites and days as the ulcerated menhaden were collected; there is no evidence of Pfiesteria toxicity.
Pocomoke River: 13 species totaling 1770 fish were collected on August 8th. Four of the five menhaden had lesions; the remaining 12 species and 1765 fish appeared healthy. There is no evidence of Pfiesteria in the water column in the region at this time.
Cambridge Creek, Choptank River basin: On August 3rd , 30 of 51 menhaden collected had ulcers. Collections made on August 4th found 10% of menhaden with ulcers and no menhaden were captured on August 7th . Genetic probe results were negative for Pfiesteria from water samples collected August 3rd . Some dead fish were observed in the area on August 10th and water samples have been collected by the Horn Point Lab.
Greenwood Creek, Eastern Bay: Fish with ulcers were observed on August 10th but no menhaden were captured in netting efforts. Water samples collected from the site were negative for Pfiesteria.
Wallace Creek, Honga River: A group of menhaden with ulcers was observed on August 17th. Sixty menhaden were collected from the site on August 18th, and all had ulcers. Water samples collected both days at the site of the ulcerated fish were positive for Pfiesteria, although there is no evidence to date of toxicity.
St. Mary's Creek, Potomac River basin: Nine menhaden were collected near Tippity Whichity Island on August 10th and 3 had ulcers. The area was revisited on August 15th and 7 of 33 of the menhaden had ulcers. Water samples collected on August 10th were negative for Pfiesteria with genetic probe testing at Dr. Oldach's laboratory.
South River: On August 12th there was a report of a fish kill. The site was visited on August 14th by Maryland Department of the Environment; 5 dead menhaden were located and water quality conditions showed low dissolved oxygen (3.5 mg O2/L) associated with an algal bloom of the dinoflagellate algae Prorocentrum minimum. A water sample collected from the site tested negative for Pfiesteria. Additional sampling on August 16th found only 5 of 174 menhaden with ulcers and improved dissolved oxygen levels in the surface waters (6-7 mg O2/L); bottom water oxygen levels were, however, very low at 1.1 mg O2 /L.
Shiles Creek, Wicomico River, Eastern Shore: A small number of menhaden were collected on August 7th but the percent of menhaden with ulcers was high for each site (2 of 2 menhaden at one location and 3 of 19 menhaden collected at a second site). Water samples tested negative for Pfiesteria.
Baywide: More than 150,000 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.
In cooperation with the Maryland Department of Natural Resources, a portable REPS facility is monitoring the water at a potential site of toxic Pfiesteria activity on the Chicamacomico River. REPS complements other on-going monitoring efforts to give early warning of potential risks to human and ecological health.
The first figure (above) shows how fish in the REPS respond through time when exposed to water with toxic Pfiesteria in the laboratory. Eight fish were exposed to a toxic Pfiesteria culture at North Carolina State University (NCSU) Pfiesteria Laboratory directed by Dr. JoAnn Burkholder and Dr. Howard Glasgow. The graph shows a rapid alarm response to Pfiesteria (6 or more of 8 fish showing stress). A brief drop-off in response between 1200 (noon) and 1800 (6 pm) on June 17 is followed by continuous alarms for the rest of the test.
This second graph shows response data from eight fish in the REPS now in use on the Chicamacomico River at Drawbridge, MD during a period when no know harmful materials were present. During this recent four day period, only a few fish showed stress responses and the REPS never reached the alarm level. If there were to be a major toxic Pfiesteria event at this Chicamacomico River site, the REPS should rapidly detect the event and automatically provide a warning to scientists at the Maryland Department of Natural Resources.
The Defense Department is one of the Agencies supporting the Federal Agencies' Chesapeake Ecosystem Unified Plan to study the effects of harmful microorganisms such as Pfiesteria on aquatic resources and human health. The U.S. Army convened a Pfiesteria work group in 1998 to identify potential hazards posed by this type of organism to military personnel. The REPS system was developed with support from the U.S. Army Medical Research and Material Command and the U.S. Army Corps of Engineers. An earlier version of REPS was developed in cooperation with the Installation Restoration Program at Aberdeen Proving Ground, MD to detect various toxins in groundwater.
The Pfiesteria detection work was made possible by a grant from the Environmental Monitoring for Public Access and Community Tracking (EMPACT) program of the U.S. Environmental Protection Agency. Grant participants include USACEHR, the U.S. Food and Drug Administration, the Johns Hopkins University/Applied Physics Laboratory, and the University of Maryland School of Medicine.
Routine Pfiesteria sampling.
Table 1. Positive Pfiesteria piscicida samples during the routine monitoring program for year 2000. (Sampling period: January 10-August 10, n=395)
Weather, Water Flow and Water Quality
Water quality conditions for the first week of August in Coastal Bays tributaries such as Ayer Creek where fish health is being intensively monitored and nearby Trappe Creek have elevated dissolved oxygen levels but lower salinity by 5 to 15 ppt versus 1998 and 1999. In Chesapeake Bay, Nanticoke River monitoring sites typically show 1-2 ppt lower salinity now than at the same time in 1998 or 1999. Dissolved oxygen levels are at or above stressful levels and tending to follow the seasonal patterns of the past 3 years. On the lower Pocomoke River, dissolved oxygen conditions near Shelltown are at stressful but not severely hypoxic conditions; downstream in Pocomoke Sound, dissolved oxygen levels are similar to values in previous three years. For Williams Point, oxygen conditions are near or above a healthy level of 5 mg O2/L. Salinity levels in the lower Pocomoke follow the pattern of those in the Nanticoke and are as much as 10 ppt lower than the first week in August between 1997-99.
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 early August show water temperatures remaining near 30 oC (about 86 Fo); dissolved oxygen levels in early August have declined to hypoxic levels (below 3 mg O2/L) at the freshwater or very low salinity stations (Cedar Hall Wharf and Rehobeth). Such levels are often considered stressful to warmwater fish under elevated temperatures. The more saline station at Shelltown shows a steady pattern of daily fluctuations at more healthy dissolved oxygen levels supporting the measurements made during biweekly monitoring. This pattern in water quality between the upstream freshwater sites and the downstream reach has been observed since 1997. Such patterns in dissolved oxygen distribution 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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