NOAA Teacher at Sea
George Hademenos
Aboard R/V Tommy Munro
July 19 – 27, 2022
Mission: Gulf of Mexico Summer Groundfish Survey
Geographic Area of Cruise: Eastern Gulf of Mexico
Date: August 25, 2022
In this post, I would like to walk you through my interactions and observations with the science research being conducted aboard the R/V Tommy Munro, in particular, the steps that were taken during a trawling process. The entire process involved three stages: Preparing for Sampling, Conducting the Sampling, and Analyzing the Sampling with each stage consisting of six distinct steps.
View the following steps in an interactive tour here: Trawl Sampling Process (Genially)
I. Preparing for Sampling
Step 1: The ship travels to designated coordinates for sampling sites as determined for the particular leg of the Survey by SEAMAP (Southeast Area Monitoring and Assessment Program).
Step 2: Once the ship reaches the site, a Secchi disk is attached to a cable and lowered into the water off the side of the ship to determine visibility. When the disk can no longer be seen, the depth is recorded and the disk is raised and secured on ship.
Step 3: A CTD (Conductivity, Temperature, and Depth) unit is then prepared for deployment. It is a rectangular chamber with sensors designed to measure physical properties of the water below including dissolved oxygen, conductivity, transmissivity, and depth.
Step 4: The CTD unit is powered on and first is submerged just below the surface of the water and left there for three minutes for sensors to calibrate. It is then lowered to a specified depth which is 2 meters above the floor of the body of water to protect the sensors from damage.
Step 5: Once the CTD unit has reached the designated depth, it remains there only for seconds until it is raised up and secured on board the ship.
Step 6: The CTD unit is then turned off and the unit is connected through a cable to a computer in the dry lab for data upload. Once the data upload is completed, the CTD unit is flushed with deionized water using a syringe and plastic tubing and then secured on the side of the ship.
II. Conducting the Sampling
Step 1: The trawling process now begins with the trawl nets thrown off the back of the ship. The nets are connected to two planks, each weighing about 350 lbs, which not only submerges the nets but also provide an angled resistance which keeps the nets open in the form of a cone – optimal for sampling while the ship is in motion.
Step 2: Once the trawl nets have been released into the water from the ship, the ship starts up and continues on its path for 30 minutes as the nets are trapping marine life it encounters.
Step 3: After 30 minutes has transpired, a siren sounds and the ship comes to a stop. The two weighted planks are pulled upon the ship followed by the trawl nets.
Step 4: The trawl nets are raised and hoisted above buckets for all specimens to be collected. Then begins the process of separation. In the first separation, the marine life is separated from seaweed, kelp and other debris. The buckets with marine life and debris are then weighed and recorded.
Step 5: The bucket(s) with marine life are emptied upon a large table on the ship’s stern for separation according to species.
Step 6: Each species of marine life is placed in their own tray for identification, examination, and measurements inside the wet lab.
III. Analyzing the Sampling
Step 1: After all species were grouped in their trays, all trays were taken into the wet lab for analysis. Each species was positively identified, counted, and recorded.
Step 2: Once each species was identified and counted, the total number of species was weighed while in the tray (accounting for the mass of the tray) and recorded on a spreadsheet to a connected computer display system.
Step 3: For each species, the length of each specimen was recorded using a magnetic wand with a sensor that facilitated the electronic recording of the value into a spreadsheet.
Step 4: Weights of the collected species were recorded for the first sample and every fifth one that followed.
Step 5: If time permitted between samplings, the sex of selected specimens for a species was determined and recorded.
Step 6:Once the entire sampling was analyzed, selected samples of specimens were placed in a baggie and stored in a freezer for further analysis with the remaining specimens returned to a larger bucket and thrown overboard into the waters. The separation table was cleaned with a hose and buckets were piled in preparation for the next sampling.
In this installment of my exercise of the Ocean Literacy Framework, I would like to ask you
to respond to three questions about the fifth essential principle (The ocean supports a great diversity of life and ecosystems.), presented in a Padlet accessed by the following link:
Remember, there are no right or wrong answers – the questions serve not as an opportunity to answer yes or no, or to get answers right or wrong; rather, these questions serve as an opportunity not only to assess what you know or think about the scope of the principle but also to learn, explore, and investigate the demonstrated principle. If you have any questions or would like to discuss further, please indicate so in the blog and I would be glad to answer your questions and initiate a discussion.