Project SE1503 Aboard NOAA Research Ship Oscar Elton Sette: Midwater Trawling & Soft-Bottom Trapping!

Big traps, Lobster traps, Minnow traps…Oh My!

June 15, 2015

Written by PIFSC guest blogger Cassie Pardee

Photos courtesy of Diona Drake and Don Kobayashi

One of the many projects on SE15-03 is the deployment of different traps to varying deep water depths (~100-300m) to sample species living in the deeper soft-bottom habitats. Each evening we deploy a group of 6 lobster pots (photo 1) and two minnow traps and then deploy the BIG trap (photo 2). I say BIG because I have been inside this trap three times now and I find it to be quite roomy (photo 3). The traps sit on the bottom overnight and in the morning we bring up the haul to see what we caught.

As the winch and crane bring up the traps from the abyss we wait with baited (!) breath to find out what’s inside. On our first deployment in Uracas the big trap came up with three comet groupers and an amber jack weighing in at 27 pounds (photos 4 and 5), but our lobster traps returned basically empty. However, during our second overnight deployment in Maug the roles were reversed. The big trap came back with nothing and our hopes were dashed, but we retrieved full lobster traps with conger and moray eels (photo 6), some shrimp, a hermit crab, and another crab species. The fun part about the trapping process is we aren’t really sure what we are going to catch each night, so it is always a surprise to see what comes up from the deep.

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Photo 1: Open lobster traps waiting to be baited

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Photo 2: Baited big trap waiting to be deployed into the water

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Photo 3: Cassie in the trap after setting up the video camera

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Photos 4 and 5: Catch from the big trap from the first overnight deployment with Uracas in the background.

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Photo 6: Moray eel from the lobster traps after the second overnight deployment

Midwater Trawling Operations!

June 15, 2015

Written by PIFSC guest blogger Allison Miller

After a slightly delayed start, we are up and running here on the Oscar Elton Sette for research project SE1503. Two days ago we visited the island called Uracas (or Farallon de Pajaros) where we deployed the SteelToe (also called SE6, a small boat which sets our the “ring-net” traps), our “BIG” trap, and our crab “pots” during the day. We call our trap “BIG” because it is very BIG (Figure 1). So big, that scientists and volunteers can sit in it (Figure 2), but don’t worry we didn’t throw it overboard until they got out.

We deployed our first midwater Cobb trawl the night we were at Uracas. At approximately 9:00pm we deployed the net. The net mouth spans 50 feet in diameter and tapers down in size to about two feet in diameter (Figure 3) where it meets our trawl “cod-end” bag. This bag is what collects most of the organisms. Before we deployed the net, we zipped the bag to the small (two foot) end of the net (Figure 4) and tied three TDRs (temperature-depth recorders) to two different points on the net (the headrope and the footrope). Then our amazing deck crew team deployed it off the stern of the ship.

This trawl followed a four-step trawl plan; the net was deployed at its deepest depth for approximately 20 min then it was moved up to a second depth for 20 min, then to a third for 20 min, and finally to a fourth depth for 20 min. At each depth it was given 15 minutes to equilibrate (called “EQ” on the radio) before the 20 minute time period began. We will follow this four-step Cobb trawl plan for the duration of the cruise, with some minor tweaks to the depths depending on patterns in the scattering layers and our desire to capture both deep-water species as well as the larval forms of insular species which are generally shallower.

At 1:00am, a few of us sleepy scientist and volunteers accumulated on the back deck of the ship and we waited as the trawl line was dragged in. At approximately 1:30am our sleepiness had been replaced with excitement as the main net came aboard the stern deck. As it came in, we carefully checked and picked organisms off the net and placed them in a small tub. By the time our trawl bag (or “goodie bag” as some called it) came aboard, our small tub was already a quarter of the way filled with pelagic fish, cnidarians, crustaceans, and a cookie-cutter shark (Figure 5)! We unzipped the trawl bag from the net and then weighed everything we collected (called the “wet weight”). After that, we began processing our catch. By 5:00am we had successfully counted, weighed, and measured everything we collected in our trawl bag (Figure 6). We were all pretty tired, but we felt proud and pleased with our first midwater Cobb trawl.

-Allison

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Figure 1: Our “BIG” trap.

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Figure 2: The “BIG” trap is so big that four small scientists and volunteers can sit in it.

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Figure 3: The trawl “cod-end” bag attached (zippered) to the rear part of the main net, which is essentially a coarse mesh plankton ring net.

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Figure 4: The main net tapers down to the trawl “cod-end” bag.

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Figure 5: Pelagic fish, cnidarians, crustaceans, and a cookie-cutter sharks collected by the midwater Cobb trawl.

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Figure 6: Example of our post-processed midwater Cobb Trawl specimens.

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