Wayne Hoggard
Fishery Biologist
NMFS, Pascagoula Laboratory

2002 Mid Atlantic Bottlenose Dolphin Aerial Surveys

Along the eastern seaboard of the United States there exists a coastal migratory stock or population of bottlenose dolphins (Tursiops truncatus). This nomadic stock of dolphins moves north and south along the coastline depending on the season and water temperature. During the summer months the dolphins are dispersed between New Jersey and south Florida. As water temperatures begin to drop in late fall, the dolphins
move south and their northern range extends only to the waters off Cape Hatteras, North Carolina. During 1987-88 a major bottlenose dolphin die off occurred along the mid Atlantic and some estimates suggest that this coastal migratory stock was reduced to only 50% of its original size. Because of the die off, the stock was declared “depleted” and therefore elevated to a status that required a more aggressive conservation plan.

Aerial surveys are one tool used by NOAA's National Marine Fisheries Service to assess and monitor populations of marine mammals . The NOAA Twin Otter aircraft was chosen because it provides a safe and versatile platform that is ideally configured to conduct marine life surveys. The aircraft has twin turbine engines, the latest in navigational and safety avionics, and plexi glass bubbles that provide observers an unobstructed view of the water and trackline. The aircraft's payload allows for the use of two independent survey teams; therefore, separate estimates can be compared, allowing a more precise population estimate. The Twin Otter is equipped with camera ports in the nose and belly of the aircraft enabling the use of high resolution digital photography and videography. A infrared thermometer is mounted in the belly that records sea surface temperatures during the entire survey.

A normal survey crew consists of a NOAA pilot and co pilot, 5 trained marine mammal observers and 2 data recorders. For each bottlenose dolphin sighting, the aircraft is diverted and the herd is circled until the species identification can be confirmed and a herd estimate obtained. This information is then entered into an onboard computer, interfaced with the aircraft’s global positioning system (GPS). Information is also recorded on sea turtles, fish schools, shipping traffic and marine pollution. These data are then used to calculate abundance or population estimates for bottlenose dolphins and any other marine life of interest.

During 2002 aerial surveys were conducted between Sandy Hook, New Jersey, and Vero Beach, Florida, to update the previous 1995 estimates. A winter (Jan. Feb.) and summer (July Aug.) period were surveyed in order to compare the distribution and population estimates between the two periods. Final results have not been published, but preliminary estimates demonstrate that the two team approach helped improve the precision and accuracy of estimates as compared to 1995. This year NOAA’s Twin Otter flew 250 hours in support of the Mid-Atlantic Bottlenose Dolphin Survey. Mid-Atlantic surveys are again planned for 2004 and the NOAA Twin Otter will be the aircraft of choice.