Aerial Surveys to Confirm Seal Haul-out Sites in Virginia

Posted on January 14, 2025

Each fall/winter, some portion of the Northwest Atlantic harbor seal population that summers in New England make their way south to Virginia. For the last decade, haul-out surveys at two distinct areas in southeastern Virginia have provided a solid baseline of data on the number of seals found on the known haul-out locations. In addition, we know from tagging studies that only a fraction of the seals in the area haul-out at any given time, so while haul-out counts provide great data, they provide an incomplete estimate of seal numbers.

Map of satellite tagged harbor seal locations in 2022

To develop better estimates of the total number of seals in the area, we need to confirm that we are counting seals at all the sites they might occupy in Virginia.  More recently we have been using time-lapse images from wildlife trap cameras to count seals and are working towards developing a “population” estimate from those counts. We know only a small number of the total seal population makes its way south, so the estimate would be for the seasonal Virginia population.

Currently, based on sighting records and discussions with local biologists, we assume that the two haul-out areas we are currently studying are the only locations were seals regularly haul-out. However, as with any hypothesis, we need to test that assumption to verify that it is true. To test that assumption, we are flying a series of coastline surveys during the winter of 2025. We are aiming for two surveys a month during peak seal season (January-March) in Virginia.

Surveys are flown from a Cessna 337 Skymaster plane, which is a twin-engine aircraft used for scientific surveys around the world. The surveys are flown at an altitude of 700-800 feet with two pilots in the front, and two observers in the back of the four-seat plane. When seals are sighted, the plane circles the seals for photographs and to document the number of seals present. It does not appear that the seals are bothered by the presence of the aircraft and remained hauled out while the plane was circling overhead.

Image from the HDR Inc and navy Aerial Survey Team of seals hauled out at the Chesapeake Bay Bridge Tunnel, image taken under NMFS scientific research permit #28184

Image from the HDR Inc. and navy Aerial Survey Team of seals hauled out on the Eastern Shore, image taken under NMFS scientific research permit #28184

This initial flight was conducted in January in conjunction with an offshore survey for whales, and covered the Virginia outer coastline, as well as some areas where seals have been sighted infrequently in the past.  During this initial survey, 56 seals were observed in total at the two known haul-out areas. No other seals were observed along the Virginia coastline.

We are planning for five more surveys during peak seal occurrence in Virginia, so check back for more results later this year.