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An Abundance of Dolphins and a Rare Bird

July 09, 2021

This week (June 22–29, 2021) we covered a variety of habitats—from nearshore off New Jersey to offshore international waters more than 200 miles off the U.S. coast.

A small gray-colored dolphin with a lighter-colored belly in mid-leap pit of the water. Clymene dolphin photographed from the NOAA Ship Henry B. Bigelow on June 25, 2021. Credit: NOAA Fisheries/Felipe Triana.

During our daytime visual and passive acoustic data collection, we covered more than 650 nautical miles and saw a high diversity of species.

It is difficult to choose a single highlight among the many outstanding species we recorded this week. However, one of the most memorable sightings was the group of some 60 Clymene dolphin that came over to the ship; thus making it the “Dolphin of the Week”.

Chart showing the East Coast from Cape Cod to Cape Hatteras and adjacent waters. Survey tracks zig-zagging colored lines
Tracklines surveyed this week in search of whales, dolphins, seabirds, sea turtles, and large fish. Credit: NOAA Fisheries.

Other contenders were warm-water species associated with the Gulf Stream, including the aforementioned Clymene dolphins, as well as spinner dolphins, black-capped petrels, Trindade petrels, and brown boobies. So far, striped dolphins (more than 700 animals) and bottlenose dolphins (more than 500 animals) have been the most abundant dolphin species sighted.

The most abundant seabird was the great shearwater, but the most memorable this week was the single white-tailed tropicbird that made a brief appearance at the end of the day on June 25. This rare sighting soars above the rest of the birds to make it the “Bird of the Week”.

A mostly white bird with a long, thin tail feather in mid-flight above the water’s surface.
White-tailed tropicbird. Credit: NOAA Fisheries/Michael Force.

Over the past week, using our towed hydrophone we recorded vocalizations from nearly all odontocete (toothed whale) families. We were particularly excited to get several high quality sound recordings from the Clymene dolphins—a first for us! We will use these recordings to enhance our passive acoustic sound library and to “train” our system to better identify sounds so we can reduce the “unidentified dolphin” category in our data.

A cable laying on the deck of the NOAA Ship Henry B. Bigelow ship.
Our towed hydrophone array. It contains three hydrophones and one depth sensor and is on loan from the NOAA Fisheries Southwest Fisheries Science Center. Credit: NOAA Fisheries.
Four track line maps
Passive acoustic detections of odontocetes collected in real-time during the HB21-02 survey. Credit: NOAA Fisheries.
A fine-mesh, sock-shaped net with a square opening supported by a rigid frame being lowered into the water from the ship.
Neuston net about to be towed just below the surface. Credit: NOAA Fisheries.

We are also on the lookout for larval bluefin tuna as part of a project to better define what may be a spawning area off the Mid-Atlantic. To maximize the chances of encountering these larvae, the night watch conducted plankton tows targeting water that is warmer than 23°C with salinities near or above 35 practical salinity units. We consecutively towed two types of nets—bongo and nueston—in a W-shaped pattern between the surface and 10 m depth. Bluefin tuna samples are preserved in ethanol to permit genetic testing. We are also removing individual salps and preserving them in the minus 80°C freezer. Dr. Ann Bucklin’s lab at the University of Connecticut will use these samples to help create a genetic species barcode for salps.

 

 

 

 

 

Debra Palka, chief scientist

Aboard the NOAA Ship Henry B. Bigelow

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Last updated by Northeast Fisheries Science Center on July 12, 2021