Preliminary Findings Related to Health Assessment Parameters for White Perch (Morone americana) From Chesapeake Bay Tributaries
Christine Densmore1, DVM, PhD; Vicki Blazer1, PhD;
Chris Ottinger1, PhD; Larry Pieper2, BS; Craig Weedon2, BS; Craig
Harms3, DVM, PhD, DACZM; Suzanne Kennedy-Stoskopf3, DVM, PhD, DACZM; John
Young4, MS; Deborah Cartwright1, MS; Paul Peach1, BS
1National Fish Health Research Laboratory, Leetown Science
Center, U.S. Geological Survey, Leetown, WV, USA; 2Maryland Department of Natural
Resources, Annapolis, MD, USA; 3College of Veterinary Medicine, North Carolina State
University, Raleigh, NC, USA; 4Aquatic Ecology Laboratory, Leetown Science Center, U.S.
Geological Survey, Leetown, WV, USA
In fall 1996 and spring 1997, watermen along the Pocomoke River, a tributary of the Chesapeake Bay
on the lower Delmarva Peninsula, noted an increased frequency of lesions among the fish in their catch. Lesions appeared
on numerous species of fish and varied considerably, ranging from small foci of petechial hemorrhage to extensive areas of
ulceration extending through the integument to underlying tissues. Some watermen also reported overall decreased body
condition among their catch. Subsequent scientific investigations undertaken to establish the cause(s) for these lesions
also revealed that there was a paucity of any previously established "normal" baseline data concerning the health of fish
within the Chesapeake Bay ecosystem.
In 1998, a cooperative 3-yr research effort between scientists from the U.S. Geological Survey, the
Maryland Department of Natural Resources, and North Carolina State University was initiated in order to establish baseline
fish health data for white perch (Morone americana), a representative species of fish, among Chesapeake Bay
tributaries, and to compare health related parameters among these fish from different tributaries. In 1998 and 1999, 24
white perch were collected from five Chesapeake Bay tributaries by net trawls at three different sampling periods (June,
August and October) each year. Data were collected from the specimens via a necropsy-based fish health assessment protocol
incorporating both gross and histologic observations and characterization of lesions. Blood was collected for hematologic
analyses including hematocrit, plasma protein concentration, and total/differential leukocyte counts. Tissue was also
collected from hematopoietic kidney and spleen for immunologic functional analyses including lymphocyte mitogenesis
assays, macrophage bactericidal assays, and cytokine (transforming growth factor - â) expression analysis. Water
quality data and watershed land use data were also collected for each sampling interval/site to further discern any
spatial differences noted in the health-related parameters.
Sampling for the first 2 yr of the study is completed and data analysis is currently underway.
Preliminary findings have established that a variety of gross lesions were apparent on the white perch from the 1998 and
1999 collections, ranging from incidental, such as mildly frayed fins to severe, such as extensive multifocal hemorrhage.
Leukocyte functional analyses indicate that significant temporal and spatial differences in immune cell function exist for
white perch in the tributaries surveyed. Hematologic data also indicate a few potential differences between sites as well
as over time.