Introduction & Objectives

The purpose of this project is to collect information and quantitative data on the seasonal occurrence, distribution, habitat use, and density of protected marine species (i.e., marine mammals and sea turtles) in the waters surrounding the Naval Air Station Patuxent River (NAS PAX) in the Chesapeake Bay. Data collected during this monitoring effort will support planning and impact assessment analyses under NEPA, MMPA, and ESA.

Technical Approach

The study area covers portions of the Chesapeake Bay as well as the mouth of the Potomac River. University of North Carolina, Wilmington (UNCW) and the Virginia Aquarium Foundation (VAQF) conducted monthly fixed-wing aerial surveys comprised of almost 600km of trackline effort covering a ~2400 km2 area. Aerial survey design followed those used in other offshore areas with similar monitoring goals.

HDR deployed and analyze data collected by C-PODs (i.e., passive acoustic data loggers) to document the seasonality and occurrence of echolocating cetaceans in the area. Photo-ID efforts from a small vessel will also be conducted opportunistically during C-POD deployments/refurbishments.
Researchers from the Center for Research into Ecological and Environmental Modelling (CREEM) at University of St. Andrews advised on survey design for both the visual data and the passive acoustic data and will analyze data from the line-transect surveys using standard design-based analysis methods.

Progress & Results

Monthly aerial surveys were conducted from April 2015 through October 2017. Bottlenose dolphins (Tursiops truncatus), loggerhead sea turtles (Caretta caretta), and unidentified hardshell sea turtles were observed in the study area, primarily during the summer months. Dolphin sightings are generally concentrated in the south-west portion of the survey area where the Potomac River empties into Chesapeake Bay. Over the course of the study, there were 24 bottlenose dolphin sightings comprised of an estimated 578 individuals.  Additionally, there were 38 sightings of loggerhead sea turtles for an estimated total of 47 animals.  

Five C-PODs were initially deployed in July 2015 and refurbished every 4-6 months.  The units were finally retrieved in November 2017. Researchers also collected opportunistic photo-identification photos from 4 different dolphin groups encountered during refurbishment trips. The first year of acoustic data corroborate the visual detections and demonstrate a summertime distribution of dolphins in the study area.  The C-POD instruments also collect ambient water temperature data that will be used to analyze occurrence patterns relative to environmental factors.

Researchers from CREEM will be applying statistical methodologies to estimate dolphin abundance and characterize any distribution patterns that may be evident in the data.  HDR will be analyzing the acoustic data to compliment results from the visual surveys. 

A comprehensive analysis of both the visual and acoustic data has been completed and a final report is now available for download.  In addition, the full data set is also available through OBIS-SEAMAP.