DUTCH CARIBBEAN — The Dutch research institute IMARES has just concluded an aerial survey for marine mammals. The work was done in support of management of the Exclusive Economic Zone (EEZ) and plans to declare the EEZ a Marine Mammal Sanctuary. Focusing on the ABC islands, they covered approximately 2,500 km of sea both north and south of the islands spotting Humpback Whales, Bottlenose Dolphins, Spotted Dolphins and Roughtooth Dolphins. But their most exciting discoveries were a Whale Shark spotted north of Aruba and a Basking Shark seen in the waters north of Curaçao.

Read the official press release by IMARES here:

Aerial surveys of whales and dolphins around ABC islands

In the first half of November, during counts from an airplane, a survey team of IMARES-Wageningen University recorded four different species of whales and dolphins around the ABC islands. In addition, researchers recorded sharks, turtles, rays and seabirds.

In total, more than twenty types of so-called charismatic megafauna were recorded. The survey was primarily aimed at determining species composition, abundance and distribution of whales and dolphins. Data on other species such as sharks , turtles , rays and seabirds were also collected.
Marine mammals recorded by the survey team were the Humpback Whale (Megaptera novaeangliae), Bottlenose dolphin (Tursiops truncatus), Spotted dolphins (Stenella frontalis and Stenella attenuata) and Roughtooth dolphin (Steno bredaensis)). The first three types are relatively common around the ABC islands. Humpback whales overwinter in the area, in summer staying in the north up to the sub-Arctic regions. Bottlenose dolphins are in the area throughout the year. Little to nothing is known about the numbers and distribution throughout the year. The two species of spotted dolphins (Atlantic spotted and Pantropical spotted dolphin) are difficult to distinguish from the air. Both species occur in the area, but quantitative data are lacking. Observations of Rough-toothed dolphin are rare. This species can easily be confused with bottlenose dolphins by less experienced observers.

Of the remaining observations two shark species are worth mentioning. A whale shark (Rhincodon typus) was seen north of Aruba. Quite remarkable was the observation of a Basking Shark (Cetorhinus maximus) north of Curacao. Observations of this species are very rare in the region. Recent research of basking sharks fitted with transmitters has shown that this species overwinters in the Caribbean or crosses the area on their way to wintering areas northeast of South America.

The aerial surveys were specifically designed for the purpose of observing whales and dolphins, but the principle is simple. A plane flies along a grid of predetermined lines, distributed over a certain area, while a survey team of experienced observers counts all marine mammals that are seen . The survey team consisted of two observers, Steve Geelhoed and Hans Verdaat, and data recorder Nicole Janinhoff, who recorded the observations data in real time as well as making additional observations. The counts were done from a twin-engine plane of Air Key West with special ‘bubble’ windows allowing observers to look under the airplane. The team operated from Hato airport, Curacao. From there they covered a total distance of about 2500 km in the Exclusive Economic Zone (EEZ) of the ABC islands. The observations were spread over twenty so-called transects. These stretched out to about 130 miles (240 km) north of the ABC islands. Roughly two-thirds of the whole EEZ was covered. Possibly in the next few years the entire EEZ can be surveyed .

The surveys are funded by the Dutch Ministry of Economic Affairs and WWF Netherlands. IMARES Wageningen University is a marine research institute in the Netherlands which studies among others coral, fish, seabirds and marine mammals.