| Virginia
Journal of Science.
2001. Vol 52 (4) : 231-239 |
| Effects
of Collection, Transport, and Redeployment Methods on Natural Mortality
of Rangia cuneata (Mactridae)
used in Biomonitoring Studies Eugene G. Maurakis, Science Museum of Virginia, 2500 W. Broad St., Richmond, VA 23220 and University of Richmond, VA 23173, David V. Grimes, Virginia Department of Environmental Quality, 629 E. Main St., Richmond, VA 23219, and William C. Gretes, University of Richmond, VA 23173 ABSTRACT
Sporadic, high mortality in test populations of wedge
clams (Rangia cuneata) has
limited the potential for using this otherwise desirable test organism
in biomonitoring studies. To determine whether high mortality was
due to ontogenic or experimental variables, a two-phased study was
conducted. In phase I, mortality of collected and re-deployed
wedge clams, subjected to varying transport conditions, was determined
at 7, 14, 21 and 60 days re-deployment. The use of three
transport times (1, 2, 3 hr.), two vehicle conditions (open, closed)
and three transport treatments (open, closed, iced containers) yielded
18 test groups. Individual test group mortalities were below 10%
through the 21 day re-deployment period and peaked at 13% at the 60 day
re-deployment point. The low rates of mortality
observed in phase I of this study indicate that reasonable collection
and transport of wedge clams does not significantly increase natural
mortality and suggests other parameters are more strongly
correlated to test population mortality. In phase II of this
study, percent survival of collected and "acutely" redeployed and
"acclimated" redeployed wedge clams was determined. Acclimated
re-deployment is the transfer of R.
cuneata from saline to freshwater in decrements of 3-4 ppt/day
in accord with recommendations in Bedford and Anderson (1972).
Acute re-deployment is the placement of R. cuneata in lower salinity waters
or freshwater without acclimation. Although percent survival of
clams acutely deployed to the freshwater test site was significantly
(p<0.05) less than the percent survival at other test sites,
mortality was only 3.3 %. No significant differences (p<0.05)
were recorded in the percent survival of acclimated redeployed wedge
clams.Keywords: Rangia cuneata, wedge clam, mortality, bioconcentratable pollutants |