Publications

Understanding the relationship between animal community dynamics and landscape structure has become a priority for biodiversity conservation. In particular, predicting the effects of habitat destruction that confine species to networks of small patches is an important prerequisite to conservation plan development. Theoretical models that predict the occurrence of species in fragmented...

A key in a different format is presented for the tadpoles of the United States and Canada. More details of ontogenetic variation are included than in many keys and more attention is paid to identifying species by using characteristics of living tadpoles.

Between 1983 and 1986 the National Wildlife Health Center (NWHC) conducted a nationwide study of lead poisoning of waterfowl from federal and state refuges. This survey was done to assist in identifying zones with lead-poisoning problems. One thousand forty one moribund or dead waterfowl were collected and examined. The presence or absence of 13 gross lesions selected as indicators of...

Data from more than 200 sites in nontidal portions of the Chesapeake Bay were compiled to document annual nutrient and sediment loads and trends for the period 1985 through 1996 as part of the 1997 Reevaluation of the Chesapeake Bay Program goal of reducing nutrient loads 40 percent by the year 2000. Annual loads were estimated by use of the Minimum Variance Unbiased Estimator (MVUE)...

No abstract available.

Assessing potential effects of flow regulation on southeastern warmwater fish assemblages is problematic because of high species richness and poor knowledge of habitat requirements for most species. Our study investigated relationships between availability and temporal persistence of key habitats and fish assemblage structure at regulated and unregulated sites in the Tallapoosa River...

No abstract available.

Estimating species richness (i.e., the actual number of species present in a given area) is a basic objective of many field studies carried out in community ecology and is also of crucial concern when dealing with the conservation and management of biodiversity. In most studies, the total number of species recorded in an area at a given time is taken as a measure of species richness...

Ground-water discharge is a significant source of nitrate load to tidal creeks, coastal estuaries, and Chesapeake Bay. Different studies have found that forest buffers greater than 200 feet wide remove most of the nitrate from passing ground water. These buffers are commonly included in regional nutrient-management strategies. Results of a U.S. Geological Survey study on the Eastern...

Protogynous wrasses (Thalassoma duperrey): females (F), primary males (PM) along with a few terminal-phase males (TM) and sex-changed males (SM), were used to characterize the topographical organization of the pituitary. In general, immunocytochemical and ultrastructural features of the adenohypo-physeal cell types of the saddleback wrasse pituitary resemble those of other teleosts. In...

The Susquehanna River contributes nearly 50 percent of the freshwater discharge to the Chesapeake Bay in a year of normal or average streamflow. The river also transports the greatest amount of nutrients (estimates of nearly 66 percent of the nitrogen and 40 percent of the phosphorus load) from all nontidal areas in the Chesapeake Bay Basin. Excessive nutrients in the Bay result in algal...

Power analysis after study completion has been suggested to interpret study results. We present 3 methods of estimating power and discuss their limitations. We use simulation studies to show that estimated power can be biased, extremely variable, and severely bounded. We endorse the practice of computing power to detect a biologically meaningful difference as a tool for study planning...