No Pfiesteria-related fish kills reported this year

UPDATE: Maryland's Pfiesteria Monitoring Activities
September 18, 1998

Fish Health

DNR continues to monitor fish health through standard assessment programs in Maryland's 23 rivers, the upper, middle and lower Chesapeake Bay, and the Coastal Bays. Nearly 300,000 fish of varied species have been examined so far this year, and, overall, Maryland fish populations are very healthy. Less than half of 1 percent of fish sampled have displayed symptoms of illness or injury, which is typical of all fish populations.

Pfiesteria Monitoring Program
No Pfiesteria-related fish kills have been reported this year.

Since April, DNR has been intensively monitoring fish health as well water and habitat quality along the tributaries that last year experienced fish kills, fish in distress and episodes of large numbers of fish exhibiting sores consistent with toxic Pfiesteria. These tributaries include the Pocomoke and Chicamacomico Rivers and Manokin River/Kings Creek. Additionally, the Nanticoke, Big Anemessex and Eastern Shore Wicomico Rivers, and two coastal bay tributaries, St. Martin and Newport Bay, are also being monitored under this program because of their similarities (in terms of water quality and physical dynamics) to last year's affected waterways.

Fish communities on these systems continue to be sampled every two weeks. Tens of thousands of fish have been examined, and nearly all have been healthy. Occasionally, fish are found with anomalies, as would be expected in normal fish populations.

Of particular interest to this program is the health of juvenile menhaden, because this species was primarily affected in last year's Pfiesteria events. Low numbers of menhaden with Pfiesteria-like sores (generally less than 10 per sample) have been periodically found in small total samples from the Pocomoke, Manokin, Eastern Shore Wicomico, Nanticoke and Chicamacomico Rivers over the last month. These findings resulted in increased monitoring in two areas, the lower Wicomico River near Shiles Creek and the Chicamacomico near Drawbridge Road, because low numbers of menhaden with sores were found for several consecutive days. All other fish species examined in these areas have been healthy. There have been no dead fish, nor any fish with lesions acting erratically.

Fish were intensively sampled for seven days in early August in the lower Wicomico River because small numbers of menhaden with lesions were found by a DNR crew of fish biologists during routine monitoring. The increased sampling yielded several dozen to a few menhaden with lesions daily, in decreasing prevalence. Fish sampling was adjusted to a weekly schedule, then eventually back to a bi-weekly schedule according to DNR's Pfiesteria monitoring program.

DNR also responded with increased monitoring of water and habitat quality on the Wicomico River and Shiles Creek. Water quality crews have taken water samples in the creek and river to measure standard water parameters (oxygen, salinity, temperature, pH), nutrients and algal communities, as well as water samples for Pfiesteria analysis. Standard water parameters at the site of the lesions have been typical for the region. While recent nutrient data has not yet been received from laboratories, the Wicomico River is generally representative of most Lower Eastern Shore tributaries in that it contains higher levels of nutrients -- phosphorus and nitrogen -- than similar tributaries elsewhere in the state.

Of six water samples taken from the lower Wicomico near Shiles Creek when menhaden with lesions were initially observed, two showed very low levels of what could be toxic Pfiesteria-like cells, per Dr. JoAnn Burkholder's lab in North Carolina. The estimated cell levels were 130 cells per milliliter (ml) and less than 50 cells per ml. To put this in perspective, Dr. Burkholder estimates that at least 100 cells per ml are necessary to cause Pfiesteria-like fish lesions. Organism species and toxicity have not yet been confirmed

A similar situation -- findings of small numbers of menhaden with lesions for several consecutive days -- occurred on the Chicamacomico River near Drawbridge Road in early September. DNR intensively sampled fish in the area for more than seven days to monitor for an escalation in the number of affected menhaden, as well as for any additional signs of possible toxic Pfiesteria activity (dead menhaden with characteristic lesions, or menhaden behaving erratically). Due to a decrease in prevalence, fish are now monitored there on a weekly basis.

Of Seven water samples taken for Pfiesteria analysis, four showed very low levels of what could be toxic Pfiesteria-like cells, per Dr. Burkholder's lab. Estimated cell levels in these four samples were less than 100 cells per ml. Organism species and toxicity have not yet been confirmed

DNR Natural Resources Police (NRP) officers are an important part of DNR's Pfiesteria monitoring program. They complement work done by DNR's fish health and water and habitat quality assessment teams by patrolling tributaries daily and conducting visual inspections for signs of possible toxic Pfiesteria activity.

Water and Habitat Quality

In addition to the above mentioned sampling for water quality and Pfiesteria analysis, water sampling to measure quality parameters has continued monthly at approximately 12 sites on each tributary in DNR's monitoring program. Site specific information continues to be received and compiled; assessments should be completed in early winter. Some comparative information is available for the Pocomoke River as follows:

Pocomoke River 1997/1998 Comparisons

Preliminary results of intensive, longitudinal sampling are now available and allow us to make some comparisons of habitat (water) quality on the Pocomoke River between 1997 and 1998. In general, it appears that nutrient levels on the river were similar in 1998 to what they were in 1997, but that heavier spring 1998 rainfall resulted in lower salinities and shifted algal concentrations further downstream than during 1997. Conditions seem to have returned to more typical levels by mid-August.

In addition to our longitudinal monitoring, we have two continuous monitoring stations that are part of the EPA-funded Environmental Monitoring for Public Access and Community Tracking (EMPACT) study. At each station, physical parameters (water temperature, salinity, dissolved oxygen, pH) are measured at the surface every 15 minutes. One station is at Cedar Hall Wharf and the other station is one mile upstream from Williams Point. Sampling began on May 18, and we receive and analyze the data once a week from the field personnel who maintain the two monitors; this data is then placed on the DNR web site at . Highlights from the data so far are:

  • Salinities have continued to increase and are back to normal levels.
  • Even though relatively little rain fell as a result of Hurricane Bonnie there were some tidal affects. The strong winds that resulted from Hurricane Bonnie resulted in higher than normal salinity and dissolved oxygen values for 2-3 days.
  • Dissolved oxygen values in the upstream site near Cedar Hall Wharf remain in the 4-5 mg/l range, which appear to be a little higher than last year's levels.


DNR's Fish Health Hotline (1-888-584-3110) has received more than 350 calls over the last month from interested citizens with questions concerning Pfiesteria. Of these calls, 104 were to report fish health problems; most of these concerned striped bass.

DNR, along with other coastal states, is analyzing the recurring problem of what is initially believed to be bacterial infections in some striped bass. The problem generally peaks in late summer, when water temperatures are highest. Scientists have agreed that the issue is not Pfiesteria.

The hotline continues to provide information to the public concerning Pfiesteria. It is also provides many opportunities to reassure the public that Maryland seafood remains delicious and safe to eat. The hotline is also a source of information for DNR's Rapid Response Teams, who comprise another valuable component of DNR's Pfiesteria monitoring program. These teams are available and on call 24 hours a day, seven days a week to respond to fish kills and fish health issues statewide.

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