NOAA Teacher at Sea
Aboard NOAA Ship Oregon II
July 9 – July 20, 2018
Mission: SEAMAP Summer Groundfish Survey
Geographic Area of Cruise: Gulf of Mexico
Date: July 15, 2018
Weather Data from the Bridge
Latitude: 30 05.44 N
Longitude: 085 52.76 W
Speed over ground: 05.3 knots
Barometric pressure: 1015.62 mbar
Relative humidity: 81%
Air temp: 27.6 C
Science and Technology Log
At the time of writing, we’ve completed the “stations” (i.e., the appointed stops where we trawl to collect specimens) in the western Gulf of Mexico, and are headed to the Florida coast, where we’ll conclude the 3rd leg of the Summer Groundfish Survey. Sometime tonight we’ll arrive and resume work, trawling and identifying fish. What follows is my attempt to furnish a detailed description of where we are and what we’re doing.
Stations: Where We Stop & Why
As I explained in my previous blog post, “Learner at Sea: Day 1,” the survey work being performed on this cruise contributes to a larger collective enterprise called SEAMAP, the Southeast Area Monitoring and Assessment Program. The “sample area” of SEAMAP is considerable, ranging from Texas-Mexico border to the Florida Keys.
Spatial coverage of SEAMAP Summer and Fall Trawl Surveys in the northern Gulf of Mexico
Fisheries biologist Adam Pollack tells me that the total trawlable area–that is, excluding such features as known reefs, oil rigs, and sanctuaries–consists of 228,943.65 square kilometers or 88,943.65 square miles. That’s a piece of ocean of considerable size: nearly as big as Louisiana and Mississippi combined.
SEAMAP divides the sample area into a series of statistically comparable “zones” (there are two zones within each of the numbered areas in the diagram above), taking into account a key variable (or stratum): depth. It then assigns a proportionate number of randomized locations to every zone, arriving at 360-400 stations for the sample area as a whole. Statisticians call this method a “stratified random design.”
While Louisiana, Mississippi, Alabama, and Florida participate in the SEAMAP, the lion’s share of stations are surveyed by NOAA.
These are the 49 stations we sampled during the first half of the cruise, off the shore of Louisiana:
Stations covered in the western Gulf during the 3rd leg of the Summer Groundfish Survey
The data from the Summer Survey is analyzed in the fall and available the following spring. NOAA’s assessments are then passed along to the regional Fisheries Management Councils who take them into account in setting guidelines.
The Trawl: How we Get Fish Aboard
NOAA Ship Oregon II brings fish aboard using an otter trawl. As described in “Mississippi Trawl Gear Characterization,” “The basic otter trawl is the most common type of trawl used in Mississippi waters to harvest shrimp. The otter trawl is constructed of twine webbing that when fully deployed makes a cone shape. Floats on the head-rope (top line) and chains on the foot rope (bottom line) of are used to open the mouth of the trawl vertically. To spread the mouth of the trawl open as large as possible, each side (wing) is attached to trawl doors” (http://www.nmfs.noaa.gov/pr/pdfs/strategy/ms_trawl_gear.pdf). Positioned by chains so that their leading edges flare out, those doors are sizable and heavy, 40 inches high and 8 feet long, and help not only to spread the net open (and ‘herd’ fish in) but also to keep it seated on the ocean floor.
An otter trawl deployed
To mitigate environmental harm–and, in particular, to help save inadvertently caught sea turtles—trawling time is limited to 30 minutes. The trawl is 40 feet wide and is dragged over 1.5 miles of ocean bottom.
Here are the trawl’s technical specifications:
Trawl schematic, courtesy of NOAA fishing gear specialist Nicholas Hopkins
It should not go without saying that deploying and retrieving gear like this is mission critical, and requires physical might, agility, and vigilance. Those tasks (and others) are performed expertly by the Deck Department, manned on the day watch by Chief Boatswain Tim Martin and Fisherman James Rhue. Fisherman Chris Rawley joins them on the swing shift, coming on deck in the evening.
The process of bringing the trawl aboard looks like this:
Trawl doors on their way up toward the starboard outrigger
Seizing the “lazy line” with the hook pole
The “elephant ear” (orange section) secured
Chief Boatswain Tim Martin brings a catch over the rail
The bottom of the trawl is secured with a special knot that permits controlled release of the catch.
Among other names, this piece of handiwork is known as the “double daisy chain” or “zipper knot”
The catch emptied into baskets
Before every trawl, the CTD is deployed from the well deck (port side) to collect data on, as its acronym suggests: Conductivity, Temperature, and Depth. According to NOAA’s Ocean Explorer website, “A CTD device’s primary function is to detect how the conductivity and temperature of the water column changes relative to depth. Conductivity is a measure of how well a solution conducts electricity. Conductivity is directly related to salinity, which is the concentration of salt and other inorganic compounds in seawater. Salinity is one of the most basic measurements used by ocean scientists. When combined with temperature data, salinity measurements can be used to determine seawater density which is a primary driving force for major ocean currents” (https://oceanexplorer.noaa.gov/facts/ctd.html).
The CTD secured on deck
The CTD suspended at the surface, awaiting descent
During daylight hours, a scientist assists with the deployment of the CTD, contributing observations on wave height and water color. For the latter, we use a Forel-Ule scale, which furnishes a gradation of chemically simulated water colors.
The Wet Lab: How We Turn Fish into Information
Once in baskets, the catch is weighed and then taken inside the wet lab.
The wet lab: looking forward. Fish are sorted on the conveyor belt (on the right) and identified, measured, weighed, and sexed using the computers (on the left).
Once inside the wet lab, the catch is emptied onto the conveyor belt
Fish ready for sorting
A small catch with a big Snapper
Next the catch is sorting into smaller, species-specific baskets:
Emily McMullen sorting fish
Say hello to the Bat Fish: Ogecephalus declivirostris
Calico Box Crab, Hepatus epheliticus
Blue Crab, Callinectes sapidus
At this stage, fish are ready to be represented as data in the Fisheries Scientific Computing System (FSCS). This is a two-step process. First, each basket of fish is entered by genus and species name, and its number recorded in the aggregate.
Andre DeBose entering initial fish data in FSCS
Then, a selection individual specimens from each basket (up to 20, if there are that many) are measured and weighed and sexed.
Andre and Emily measuring and sexing fish
Occasionally researchers from particular laboratories have made special requests for species, and so we label them, bag them, and stow them in the bait freezer room.
Special requests for specimens
Red Snapper, Lutjanus campechanus, for Beverly Barnett
Once every animal in the trawl has been accounted for and its data duly recorded, it’s time to wash everything down and get ready to do it all over again.
Late afternoon view from the wet lab porthole
The key to enjoying work in the wet lab is, as I see it, the enduring promise of novelty: the possibility of surprise at finding something you’ve never seen before! For me, that promise offsets the bracing physical rigors of the work and leavens its repetitiveness. (Breathtaking cloudscapes and gorgeous sunsets do, too, just for the record. Out here on the water, there seem to be incidental beauties in every direction.) Think of the movie Groundhog Day or Camus’s “The Myth of Sisyphus” and cross either of them with the joys of beach-combing on an unbelievably bounteous beach, and you’ll have a sense of the absurd excitement of identifying fish at the sorting stage. Life in the wet lab is a lot like Bubba Gump’s box of chocolates: “You never know what you’re gonna get.”
At the next stage, data entry, the challenge for the novice is auditory and linguistic. Between the continual growl the engine makes and the prop noise of the wet lab’s constantly whirring fans, you’ve got the soundscape of an industrial workplace. Amid that cascade of sound, you need to discern unfamiliar (scientific) names for unfamiliar creatures, catching genus and species distinctions as they’re called out by your watch-mates. The good news is that the scientists you’re working with are living and breathing field guides, capable of identifying just about any animal you hold up with a quizzical look. It’s a relative rarity that we have to consult printed guides for IDs, but when we do and that task falls to me, the shell-collector kid in me secretly rejoices.
I found it! Ethusa microphthalma (female)
I’m enjoying the camaraderie of my watch, led by Andre DeBose, and, as my posts suggest, I’ve had some good opportunities to pick Adam Pollack’s brain on fisheries issues. My partner in fish data-entry, Emily McMullen–an aspiring marine scientist who’ll be applying to graduate programs this fall–did this cruise last summer and has been an easy-going co-worker, patient and understanding as I learn the ropes. I’ve also had some wonderful conversations with folks like Skilled Fisherman Mike Conway, First Assistant Engineer Will Osborn, and Fisheries Biologist Alonzo Hamilton.
It’s been a busy week, as you’ll have gathered, but I’ve still managed to do some sketching. Here’s a page from my sketchbook on the CTD:
Sketch of the CTD. The main upright tanks, I learned, are Niskin Bottles
And here’s a page from my journal that pictures three species we saw quite often in the western Gulf:
Longspine Porgy (Stenotomus caprinus), Butterfish (Peprilus burti), and Brown Shrimp (Farfanepenaeus aztectus)
Had I the time, I’d sketch the rest of my “Top 10” species we’ve seen most commonly in the western Gulf. That list would include (in no particular order): the Paper Scallop, Amusium papyraceum; Lookdown, Selene vomer; Blue Crab, Callinectes sapidus; Squid, Loligo; Lizardfish, Synodus foetens; Croaker, Micropogonias undulatus; and Red Snapper:
Presented for your inspection: Red Snapper, Lutjanus campechanus
Did You Know?
Four of the species visible on the surface of this basket have been identified in the blog post you’ve just read. Can you ID them? And how many of each would you say there are here on the surface?
Basket of fish
Look for a key in my next blog post.