NOAA Teacher at Sea
Aboard NOAA Ship Oregon II
July 9 – 20, 2018
Mission: Summer Groundfish Survey
Geographic Area of Cruise: Gulf of Mexico
Date: July 19, 2018
Weather Data from the Bridge
Latitude: 29 57.6 N
Longitude: 087 02.60 W
Speed over ground: 7.3 knots
Barometric pressure: 1014.49
Relative humidity: 84%
Air temperature: 26.8 C
Sea wave height: 1 m
Science and Technology Log
We arrived off the coast of Florida on the evening of Sunday, July 15, and sampled stations in the eastern Gulf until the afternoon of Thursday, July 19. We used the same fishing method during this part of the cruise (bottom trawling), but added a step in the process, deploying side scan sonar in advance of every trawl. This measure was taken both to protect sea life on the ocean floor (sponges and corals) and to avoid damaging equipment. The sea bottom in this part of the Gulf—east of the DeSoto Canyon—is harder (less muddy) and, in addition to coral and sponge, supports a number of species markedly different than those seen in the western Gulf.
Side Scan Sonar
In contrast to single-beam sonar, which bounces a single focused beam of sound off the bottom to measure depth, side scan sonar casts a broader, fan-like signal, creating nuanced readings of the contour of the ocean floor and yielding photo-like images.
When we arrive a station in this part of the Gulf, we begin by traversing, covering the usual distance (1.5 miles), but then turn around, deploy the side scan sonar, and retrace our course. Once we’ve returned to our starting point, we recover the sonar, turn around again, and—provided the path on the sea bottom looks clear—resume our course through the station, this time lowering the trawl. If the side scan reveals obstructions, it’s a no-go and the station is “ditched.”
And Now for Something Completely Different . . . Fish of the Eastern Gulf
We spent the first half of this leg of the survey in the western Gulf of Mexico, going as far west as the Texas-Louisiana border. The second half we’re spending in the eastern Gulf, going as far east as Panama City. From here we’ll work our way westward, back to our homeport in Pascagoula.
Thanks to different submarine terrain in the northeastern Gulf—not to mention the upwelling of nutrients from the DeSoto Canyon—it’s a different marine biological world off the coast of Florida.
Here’s a closer look at the submarine canyon that, roughly speaking, forms a dividing line between characteristic species of the western Gulf and those of the eastern Gulf:
And here’s a selection of the weird and wonderful creatures we sampled in the eastern Gulf. As this basket suggests, they’re a more brightly colored, vibrant bunch:
Video credit: Will Tilley
Our move into the eastern Gulf marks the midpoint of the cruise, and we’ll be back to Pascagoula in a few short days. The seas haven’t been as serenely flat as they were in the eastern Gulf, nor has the sky (or sea) been its stereotypically Floridian blue, but I’ve found life aboard ship just as pleasurable and stimulating.
In my final blog post, I’ll have more to say about all the great folks I’ve met aboard NOAA Ship Oregon II—from its Deck Department members and Engineers, to its Stewards and NOAA Corps officers and inimitable Captain—but here want to reiterate just how thoughtful and generous everybody’s been. The “O2” is a class act—a community of professionals who know what they’re about and love what they do—and I couldn’t be more grateful to have visited their world for a while and shared their good company.
Busy as we’ve been, I haven’t had much time for sketching during this part of the cruise, and, as the selection of photos above suggests, I’ve concentrated more on taking pictures than making them. Still, I’ve begun a small sketch of the ship that I hope to complete before we reach Pascagoula. It’s based on a photograph that hangs in the galley, and that I’m going to attempt to reproduce actual size (3 3/8” x 7”) . Here’s where things stand early on in the process:
Did You Know?
Any of the western Gulf fish in the basket from my last blog post? Here it is again:
And here is a visual key to the four species I was fishing for, each figuring prominently in my blog post for July 15:
1: Red Snapper, Lutjanus campechanus
2: Longspined Porgy, Stenotomus caprinus
3: Gulf Butterfish, Peprilus burti
4: Brown Shrimp, Farfantepenaeus aztecus
A few Stenotomus caprinus and Peprilus burti have been left unhighlighted. Can you find them?