Jeff Peterson: The Work in the Eastern Gulf, July 19, 2018


NOAA Teacher at Sea

Jeff Peterson

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

Date: 2018/07/19

Time: 16:34:47

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.

Towed Side Scan

How side scan sonar works: The harder the object, the stronger the image returned. See: https://oceanservice.noaa.gov/education/seafloor-mapping/how_sidescansonar.html#

 

Side scan sonar device

Side scan sonar device in its cradle.

 

 

Rigged and ready for deployment.

Rigged and ready for deployment. Signals from the sonar are conducted up the cable and picked up by the electrically powered lead on the block.

 

on its way in

Side scan sonar on its way in astern.

 

descending

Side scan sonar just beneath the surface & descending.

 

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.”

 

Coming about

Coming about before deploying the side scan sonar.

 

 

And Now for Something Completely Different . . . Fish of the Eastern Gulf

Panama City, Florida

Off Panama City, Florida – Tuesday morning, July 17, 2018

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:

Bathymetric map of the Gulf of Mexico

Bathymetric map of the Gulf of Mexico, with proposed dive sites for Operation Deep-Scope 2005 indicated by red arrows and yellow numbers. Site #1 is on the southwest Florida Shelf in the Gulf of Mexico, where deep-water Lophilia coral lithoherms are found. #2 is DeSoto Canyon, a deep erosional valley where upwelling of deep nutrient rich water means greater animal abundances. #3 is Viosca Knoll, the shallowest site, where spectacular stands of Lophelia provide abundant habitat for other species. See: https://oceanexplorer.noaa.gov/explorations/05deepscope/background/geology/media/map.html

 

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:

Basket of catch

A basket of fish. Upper right: Lane Snapper, Lutjanus synagris. On the left: Sand Perch, Diplectrum formosum. The plentiful scallops? Argopecten gibbus.

 

 

Sand Perch, Diplectrum formosum

Sand Perch, Diplectrum formosum

Razorfish, Xyrichtys novacula

Razorfish, Xyrichtys novacula

A basket of Xyrichtys novacula

A basket of Xyrichtys novacula

 

Angelfish, Holacanthus bermudensis

Angelfish, Holacanthus bermudensis

Angelfish closeup

Holacanthus bermudensis details: tail fins (front specimen), pectoral fin & gill (behind)

 

Jackknife Fish, Equetus lanceolatus

Jackknife Fish, Equetus lanceolatus

Lined Seahorse, Hippocampus erectus

Lined Seahorse, Hippocampus erectus

 

 

Argopecten gibbus

Argopecten gibbus (all 2,827 of them)

Pink Shrimp, Farfantepenaeus duorarum.

Pink Shrimp, Farfantepenaeus duorarum. Note the signature “pink” spot by my thumb.

 

Calamus

Calamus

 

Lionfish, Pterois volitans

Invasive scourge of the Gulf: Lionfish, Pterois volitans

Lionfish, Pterois volitans

Lionfish, Pterois volitans

 

Burrfish, Chilomycterus schoepfii

Burrfish, Chilomycterus schoepfii

 

 

Scorpionfish (aka Barbfish), Scorpaena brasiliensis

Scorpionfish (aka Barbfish), Scorpaena brasiliensis

 

Southern Stargazer, Astroscopus y-graecum (juvenile)

Southern Stargazer, Astroscopus y-graecum (juvenile)

 

Ocellated Moray Eels, Gymnothorax saxicola

Ocellated Moray Eels, Gymnothorax saxicola

 

Trumpetfish, Aulostomus maculatus

Trumpetfish, Aulostomus maculatus

 

 

Video credit: Will Tilley

 

debris

Mysterious debris: A bottom-dwelling payphone?

 

Personal Log

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.

storm

A squall on Monday morning, July 16, 2018. Off the stern there to starboard, Blackfin Tuna were jumping.

 

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:

IMG_8230 2.jpg

Work in progress: sketch of NOAA Ship Oregon II

 

Did You Know?

Any of the western Gulf fish in the basket from my last blog post? Here it is again:

Basket of Fish from Western Gulf

Basket of Fish from Western Gulf

And here is a visual key to the four species I was fishing for, each figuring prominently in my blog post for July 15:

Basket of fish revision

Basket of Fish from Western Gulf: now color-coded

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?

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