Seal Surveillance Continues!

Posted on February 5, 2024

About 10 years ago, a NAVFAC LANT researcher noted that the NOAA Stock Assessment Reports stated that the southernmost extent of the range for gray and harbor seals was New Jersey, despite increasingly regular sightings of both species every winter in Virginia. This initiated a study to monitor both species at two major haul-out sites in southeastern Virginia from fall to spring each year, and subsequently expanded to the use of wildlife camera traps and satellite tagging. These annual haul-out surveys led to the range extent being updated to include Virginia in 2018 for harbor seals and in 2021 for gray seals.

Harbor Seals at the Chesapeake Bay Bridge Tunnel in January of 2024. NMFS General Permit # 19826.

The haul-out counts and camera trap studies are continuing this winter, and have been in full swing. So far, there have been 12 haul-out surveys since November 2023—6 at the Chesapeake Bay Bridge Tunnel, and 6 at a haul-out location on the barrier islands of Virginia’s Eastern Shore, with the highest counts of the season so far being 38 and 23 seals at these sites, respectively. Unlike previous seasons, no gray seals have yet been sighted, only harbor seals. Individual seals can be identified as unique individuals by the marks and coloration of their fur. Our photo-ID catalog of seals contains 170 individual harbor seals and 1 gray seal from the 2015-2022 seasons.  Of the 170 harbor seals, 88 (52 percent) were observed only once and 82 (48 percent) were re-sighted on more than one occasion across the seven field seasons, indicating that these seals exhibit seasonal site fidelity to the lower Chesapeake Bay and coastal Virginia waters.

Harbor Seals at the Chesapeake Bay Bridge Tunnel in January of 2024.  NMFS General Permit # 19826.

A drone is often utilized at the Eastern Shore location in order to obtain an overhead count to compare to the vessel counts made by marine mammal observers. NAVFAC is working on the logistics to also add a thermal camera to the Eastern Shore location in order to obtain counts of hauled out seals at night when the other cameras are not able to collect data. Results from the tagging project indicated that harbor seals spent more time hauled out at night rather than during the day, so current counts may be underestimating the number of seals using these haul-out locations.

For more information on this project, see the project profile for Haul-Out Counts and Photo-Identification of Pinnipeds in Virginia.

Harbor Seals at the Chesapeake Bay Bridge Tunnel in January of 2024.  NMFS General Permit # 19826.