A Quiet Place (in the Gulf of Mexico)

Day 31 and 32

Welcome back, survey followers!

After a slight delay, NOAA Ship Gordon Gunterdeparted on the afternoon of July 27 for the third and final leg of the 2024 Vessel Survey for Abundance and Distribution of Marine Mammals and Seabirds. The team has been working hard all summer. Now, with some new folks joining our ranks, we are ready to make the final push toward the western Gulf of Mexico. We steamed all night to make it west of the Mississippi River Delta.

The bird observers were back at it on Saturday afternoon. They began surveying just south of the Mississippi barrier islands while we transited to the start of our survey lines for this leg. That afternoon and evening they saw many schools of fish, some of which seemed to attract hungry birds. The bird team spotted sandwich terns, royal terns, laughing gulls, black terns, and an Audubon's shearwater. They also saw several small groups of bottlenose dolphins, and even some tuna. Sunday began slowly with a distant, poorly lit, unidentifiable large gull. Later, the bird team briefly saw a masked booby, followed by a string of brown boobies throughout the day. They also spotted a royal tern, two sandwich terns, a Cory's shearwater, and an Audubon's shearwater.

Sunday was busy for the acoustics team, with 22 detections. Most of these were dolphins, but they heard one excellent beaked whale vocalization! They also heard seismic airguns, many oil rigs, and even a squeak originating from somewhere on the Gordon Gunter. Thankfully, a change in the ship's speed resolved the squeak, which was a huge relief to the acoustic team's ears!

The marine mammal team had a steady day of sightings, which was great for getting back in the swing of observing as we began this final leg. They recorded 15 sightings throughout the day, mostly dolphins and a few sperm whales. They were able to identify bottlenose, stripedand pantropical spotted dolphins.

That concludes our weekend update. Goodnight and have a pleasant tomorrow!

Day 33

Greetings followers,

The survey team spent the day far offshore in a quiet space between the Loop Current to the east and a Loop Current eddy to the west. Viewing conditions were moderately good and sightings were slow. The marine mammal team had only one sighting-unidentified dolphins-which made for a very long day. The acoustics team spent the morning troubleshooting equipment, which meant they could not collect data until later in the afternoon. Once they began recording, there were sadly no acoustic detections the rest of the day.

The bird team began the day with boobies! Two brown boobies visited the ship before 7:30 a.m. and a few more came by to pick off some flying fish during the day. After lunch, an immature red-footed booby visited-the first of this leg-and the booby least encountered on these surveys. We only recorded two on Leg 1, and four on Leg 2, so this was an exciting sighting! This worn red-footed booby showed off its skill at catching flying fish above the surface, versus on a dive like most brown boobies do. It was successful once or twice, displaying acrobatics not often seen in the larger booby species.

The marine mammal team spotted a young masked booby in the big eyes-the large binoculars we use to sight distant animals. The bird team spotted a few other seabirds: Cory's and Audubon's shearwaters plus a band-rumped storm-petrel. The other species we encountered were more land lovers (though all are known for their oceanic wanderings): barn swallow, brown pelican, laughing gull, and royal tern. The laughing gull was quite worn and barely had any tail feathers at all! It spent some time preening on the ship before jumping off after our turn onto our new trackline. We were also lucky to see an Atlantic mahi mahileaping out of the water in pursuit of some flying fish! Overall, quite a productive day for the bird team!

Hopefully tomorrow will be busier as we head inshore toward a Loop Current eddy edge. These oceanographic features tend to bring up nutrients from the depths of the ocean that help produce more food for small fish-and therefore, more food for birds and marine mammals!

Day 34

Hello survey followers,

The crew pushed farther west today. We had a favorable sea stateof about 2 for most of the day, but there wasn't much cloud cover which made for especially hot survey conditions. The marine mammal visual team had a slightly more interesting day than Monday, with 10 sightings. There were a few sightings of pantropical spotted dolphinsthat were possibly one very spread out group. Each visual team also saw a group of pilot whalesat the same time, but at different bearings and 1.5 miles apart. This survey has two visual teams that operate independently, so that it's possible to have independent sightings. A goal of the two-team survey design is to estimate what only one team might miss. The pilot whale sightings were a good example of this design in action. The whales may have been part of a loose group, which are often widely spaced but in communication with each other. As we approached the northern end of our track, we counted some bottlenose dolphin groups and other unidentified dolphins.

Tuesday was a busier day for the acoustic team. It started off slow but steady and then picked up momentum as we approached the shelf. Of the 11 acoustic detections, 10 were unidentified dolphins. Steaming north towards shallower waters comes with an increase in industrial activity. That afternoon, we detected a seismic vessel used to survey the seabed, and its operations could be heard over 10 kilometers away. This gave us a stark reminder of the ocean noise endured by marine life in the Gulf of Mexico on a daily basis.

Today, the bird team squeezed out double-digit bird sightings! The bird numbers were buoyed by the influx of mostly younger brown boobies opportunistically feeding on the flying fish that the Gunter flushed up. To round out the rest of the day, we had additional sightings of royal terns, Audubon's shearwaters, a lone juvenile barn swallow, and a few band-rumped storm-petrels. Hopefully as we continue southward again on the next line, we will enter into more interesting waters and currents-and therefore more species.

Moving along!

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