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Another Week, More Surprises at Sea

August 27, 2021

During August 4–10, 2021 on Leg 2 of the 2021 AMAPPS abundance survey, we worked mainly in Canadian waters on the southern edge of Georges Bank, farther south to the Gulf Stream, and in international waters.

Two images side by side. Left image shows 6 to 7 common dolphins diving together at the water’s surface. They are dark on the top with light colored bellies. Right image shows two dark-colored Atlantic spotted dolphins swimming on the surface. Common dolphins (A) and a mother and calf Atlantic spotted dolphins (B) photographed during Leg 2 of the AMAPPS abundance survey on the NOAA ship Henry B. Bigelow. Credit: NOAA Fisheries
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Chart displays the latitude and longitude of the sighting area. Water temperatures are represented by colors with cooler waters inshore and warmed waters further from shore. White circles denote sightings of Atlantic spotted dolphins. These are farther offshore in deeper waters. Black triangles denote sightings of common dolphins, and these are closer to shore in shallower waters.
Distribution of Atlantic spotted (white circle) and common dolphin (dark triangles) sightings, overlaying the track lines (black line) and the sea surface temperatures reported for August 8, 2021. Credit: NOAA Fisheries

Since the start of this leg on July 23 through this week, we have surveyed about 830 nautical miles. Unfortunately, some 180 of those miles were covered during strong Beaufort wind force scale 5 and 6, not the best conditions for detecting cetaceans using high-powered binoculars. Beaufort scale 5 or 6 winds are considered fresh to strong breezes, with wind speeds between 19 and 31 miles per hour. However, since that is all Mother Nature gave us, we will adjust the analyses accordingly.

Mother Nature also gave us warmer waters than we had seen before, and the observed distributions of cetaceans changed accordingly. Each species has its preferred water types. Common dolphins were in waters cooler than about 22°C (about 71.6°F), while Atlantic spotted dolphins liked it hot!

Seabird Team

The bird is in flight with the ocean in the background. It has a black-and-white head, its wings are slender, pointed, and black-tipped, and its tail is forked.
Least tern, the world’s smallest tern. Credit: NOAA Fisheries/T. Johnson

The bird team had another fantastic week with high diversity and several remarkable sightings. In this week alone we saw 21 species. Choosing a single highlight among the many is no easy task. For example, the least tern we saw southeast of Cape Sable, Nova Scotia is rarely seen anywhere in Canada. We also saw a young masked booby. This sighting is only the fourth or fifth ever recorded for this species in waters off Massachusetts, and a first for an AMAPPS cruise. 

The light colored bird is in flight, traveling away from the photographer. Its long, slender black-tipped wings are lifted, with the sky in the background
A masked booby. This large, long-winged, white-and-black seabird is found in tropical oceans and off our southern Atlantic and Gulf coasts. It is a rare visitor to North America, and also called the masked gannet or blue-faced booby. Credit: NOAA Fisheries/T. Johnson

The other scarce species seen this week are more commonly associated with warmer water and typically found farther south than our study area. These warm-water species included two red-billed tropicbirds, a single white-tailed tropicbird, and a brown booby. In keeping with the warm-water theme, this week we also saw many Audubon’s shearwaters, more commonly seen in more southerly waters.

Passive Acoustics Team

The acousticians were thrilled to recognize beaked whale vocalizations in real time out in the field! Beaked whale echolocation clicks are too high in frequency for humans to hear without help. We can identify different species by turning unique combinations of time, frequency, and intensity into an image, called a Wigner plot.

 Three color plots with unique light shapes representing vocalization patterns of Cuvier’s, Sowersby’s and Trues/Gervais’ beaked whales.
Wigner plots of beaked whale clicks analyzed by acousticians Samara Haver and Jennifer Wallace-Turek in real time on AMAPPS 2021 – Leg 2. From left to right: Cuvier’s beaked whale (A), Sowerby’s beaked whale (B), and True’s/Gervais’ beaked whale (C). Credit: NOAA Fisheries

On August 10 we had a rare treat: several long acoustic recordings of beaked whales, probably captured because the animals were on a deep dive close to our trackline. We recorded a Cuvier’s beaked whale for about 11 minutes and a True’s/Gervais’ beaked whale for about 20 minutes. The length of the True’s/Gervais’ recording aligns with what we know of the True’s beaked whale group vocal period duration, as documented on other surveys. 

In contrast, the Sowerby’s beaked whale vocalizations recorded were only about 10 seconds, and we recorded only about six clicks. Just catching the Sowerby’s vocalization was exciting since the high frequencies emitted from this species are difficult to record. Picking out these vocalizations is like finding a needle in a haystack!

Night Ops Team

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 three rows, two images each, all with black backgrounds and tiny, light-colored animals.
Video plankton recorder images. Clockwise from top right: a peneid shrimp, a hydromedusa, a gastropod veliger, krill, a crab megalopa and a larval fish. Credit: NOAA Fisheries

The night watch completed a conductivity, temperature, depth transect across the Northeast Channel, staying just south of the Canadian longline fishing fleet. The Northeast Channel separates the northernmost part of Georges Bank from Browns Bank and is in Canadian waters. The following night we conducted video plankton recorder (VPR) tows highlighting the variable oceanography and diverse plankton in the slope environment. We took advantage of being in warm, salty Gulf Stream eddies to sample for bluefin tuna larvae. 

We were shadowed by schools of small jacks and flying fish, attracted to the lights on our side-sampling station. Last, we did a series of parallel VPR tows above Physalia Seamount finishing just before a series of thunderstorms moved into the area. The VPR continues to capture astounding pictures.

 

Debra Palka

Chief Scientist, Leg 2

Aboard the NOAA Ship Henry B. Bigelow

 

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Last updated by Northeast Fisheries Science Center on August 31, 2021