Day 24
On Friday, we headed southwest down one of our longest transect lines—which was about 200 nautical miles in length—in the central Gulf of Mexico. We started the day in waters that were about 100 meters deep and quickly headed down the continental slope to deeper waters. Survey conditions were amazing with flat seas and partly cloudy skies. Both the visual and acoustic teams had that warm fuzzy feeling that it was going to be a good day.
The acoustics team reported the freshly cleaned propellers may have been magic, because abracadabra, the Gordon Gunter was back to being a super quiet ship. Reduced noise from the ship means the hydrophone array has a better chance of detecting marine mammal vocalizations. The team heard a record-breaking 19 acoustic detections—including 11 detections of sperm whales encompassing more than 20 individuals! Other detections included various dolphin species and an unidentified beaked whale.
The visual team almost lost themselves in a pile of sighting sheets today, with 33 total sightings! They started with bottlenose dolphins, but the species quickly switched to deep water ones. The team sighted a large group of pilot whales, spread out over at least a mile in front of the ship. We rarely see elusive species like pygmy sperm whales, dwarf sperm whales, and beaked whales. Due to great viewing conditions, six of the team’s sightings were of these species. They also saw the usual host of dolphins, including pantropical spotted dolphins and striped dolphins. No matter how many dolphin species we see, a survey doesn’t feel complete without Clymene dolphins. Today, a group swam quickly to the Gordon Gunter’s bow to swim in the pressure wave. The team also had several sperm whale sightings, including one that passed closely down the port side of the ship.
This morning the bird watch was slow. Other than a magnificent frigatebird spotted in the distance during off-survey time, not even a flying fish broke the monotony. As the ship moved offshore into deeper water and salinity increased, the bird team finally began to see flying fish again. They also saw laughing gulls and royal terns, and some of the terns followed the ship farther offshore. The sighting of the day was a new species for Leg 2—a small flock of about 30 Wilson's storm-petrels feeding over some fish! These small seabirds nest in the southern hemisphere, some all the way down in Antarctica. Many of them make an annual journey north, with some traveling all the way up to Canada! As the water became our favorite shade of blue and the seaweed density increased, we began to see more seabirds like Audubon's shearwaters and Cory's shearwaters. Also of note were some feeding sooty terns, one sub-adult brown booby, and one masked booby that was likely under 1 year old. The bird observers teeter totter between their bird sightings and capturing amazing photos of birds, marine mammals, and other sea life. These opportunities come once in a lifetime (or maybe once a survey), so they definitely make the most of it!
Days 25 and 26
Happy Monday, survey enthusiasts.
We spent the weekend far offshore in deep water, even getting close to the border of U.S. and Mexican waters. For the most part, the weather was great with an average sea state of Beaufort 3. The visual and acoustic detections were plentiful.
The marine mammal visual team had a relatively steady weekend, with 26 visual detections on Saturday and 14 on Sunday. We observed the usual deep-dwelling species including sperm whales, beaked whales, and dwarf or pygmy sperm whales. We also saw pilot whales, rough-toothed dolphins, Risso’s dolphins, and several groups of pantropical spotted dolphins. We even managed to get a couple biopsies from the pantropical spotted dolphins that approached the ship. Biopsy samples provide genetic data to identify individuals and aid in population assessments. They can potentially be used to sample tissues for stable isotopes, lipid composition, and other data to better understand the animals’ diet and condition. The highlight of the weekend was a sighting we initially thought were killer whales. As we got a better view, we realized they were false killer whales (aptly named). We took advantage of the sighting and got two biopsy samples from the group before continuing on our track to finish the day.
On Saturday morning, the acoustic detections flooded in as we approached the edge of the Loop Current, starting with a sperm whale encounter followed closely by some beaked whale species. Later on, the team detected some rough-toothed dolphins’ whistles on the hydrophone array. The day ended with a chorus of false killer whales. In total, the acoustic team had 17 detections. Sunday also began with excitement—a sperm whale detection that contained 13 individuals and lasted almost an hour! The remainder of the day was quieter with a few unidentified toothed whales. We ended the day with a nice little nightcap of dolphins whistling into the sunset.
For the bird team, Saturday started with a fair amount of activity, but by mid-afternoon we were in no-birds-land. Fortunately, things picked back up again after dinner. We sighted a few Audubon's shearwaters, several brown boobies, some band-rumped storm-petrels, a royal tern, an unidentified jaeger, two unidentified storm-petrels, and two barn swallows. The two most exciting birds of Saturday were a black-and-white warbler and a brown noddy. The sightings of the warbler and swallows suggest the first wave of migration might be starting to hit us in the central Gulf of Mexico; we will see what other migrants we spot in the coming days.
Sunday conditions were beautiful with seaweed scattered around us. It was organized into windrows, and even some nice current edges, with large patches of more than 5 square meters! This made for perfect conditions for seabirds and flying fish. While we saw both, they were not present in the numbers we hoped for with such nice habitat. In the morning we saw the usual brown boobies and a distant tropicbird. A red-footed booby made an appearance, tacking back and forth across the bow targeting flying fish. There were only a couple of these gorgeous, streamlined boobies on the last leg and we've already doubled that count. (Competition? You bet!) Sooty terns seem to be showing up more regularly. We saw a few feeding flocks today, some associated with Audubon's shearwaters. We also saw a couple of band-rumped storm-petrels traipsing across the bow, and passed a nice flock of 15 Cory's shearwaters sitting on the water. It was a good weekend for the bird team.
Day 27
The survey group woke up with a new view, after transiting overnight to a different transect line. We started the day heading southeast, dodging several oil rigs and drillships that requested a wide, 2-mile clearance. Sighting conditions were variable, but overall relatively good.
Navigating around oil rigs and drillships in shallower waters meant a noisy morning for the acoustic team. Oil rigs, drillships, and the vessels that service them, have distinct sounds that contribute to the soundscape of the area. After passing through the noisier area with rigs and drilling, the marine mammal detections started to come in for a total of nine today.
Today was a slow day on the bird front. We saw only eight species of birds, which was one of our lowest count days of Leg 2. We saw a lone Audubon’s shearwater and band-rumped storm-petrel in the morning. We had intermittent brown booby guests throughout the day that peaked at nine individuals soaring around us at once, after a close pass by a rig in the afternoon. We also saw a handful of royal terns come in for a quick flyby. A lone barn swallow flew in over the flying bridge canopy, only to pull a Houdini and disappear without a trace. At the end of the day we had a feeding flock composed of sooty terns, Audubon’s shearwaters, and a single Cory’s shearwater. We added a small flock of 11 lesser yellowlegs to our list of migrants.
The marine mammal visual team had 18 sightings today, but it seemed slow because most of them were distant, unidentified dolphin groups. The groups we identified were bottlenose dolphins and pantropical spotted dolphins, pilot whales and sperm whales.
Shout out to Kate Sutherland for taking amazing photos every day! I wish I could include all of them.
