Bubbles or not, here we come!

By Andrew Gray
Andrew Gray pre-breathes to prepare his rebreather for five minutes prior to entering the water for a Stationary Point Count fish survey dive.

Andrew Gray pre-breathes to prepare his rebreather for five minutes prior to entering the water for a Stationary Point Count (SPC) fish survey dive.

Something was different on the recent PIFSC Main Hawaiian Islands Reef Fish Survey cruise led by the Coral Reef Ecosystem Division (CRED). In addition to the usual scuba surveys conducted by scientists, the small boats also deployed scientific divers that resembled a species of bionic frogmen. Instead of scuba, these divers used closed circuit rebreathers (CCR), and while it may look like they were a bit overdressed for the occasion, there was a good reason for it.

When conventional open circuit scuba divers take a breath of air from the tanks on their backs, they exhale it into the surrounding water and create a burst of bubbles containing CO2, residual oxygen not metabolized by the body, and nitrogen, an inert gas. Closed circuit rebreathers (or just rebreathers) are a specialized type of dive equipment that removes the CO2 and re-uses the exhaled oxygen. The diver breathes from a “loop” of gas where CO2 is removed from the exhaled gas by a chemical filter called a “scrubber.” Three oxygen sensors analyze the gas and a computer-controlled solenoid adds additional oxygen to replenish oxygen metabolized by the diver or add more oxygen when specified by the diver. Rebreathers include two small tanks of gas, one of pure oxygen and a second of a gas to dilute the oxygen called the diluent, usually air for depths less than 130 feet.

Closed circuit rebreather (CCR) diver Ray Boland poses with open circuit diver Kristin Golman despite her loud and annoying exhales.

Closed circuit rebreather (CCR) diver Ray Boland poses with open circuit diver Kristin Golman despite her loud and annoying exhales.

This equipment has a number of benefits over conventional scuba. The efficient use (and re-use) of gas allows divers to stay underwater much longer without having to bring an excessive number of tanks. Since the rebreather is mixing an ideal nitrox gas mix for whatever depth the diver is at, rebreather divers can have much longer no-decompression dive times when compared with conventional scuba divers at the same depth. Also, because no air is released into surrounding water, there are no bubbles or noisy exhalations—and that is exactly why we are using them.

It’s understood that visual fish surveys may be prone to certain biases. One of which is that fish behavior may be altered by the presence of a diver in the water. Some fish species may be attracted to the diver, others afraid. In areas where spearfishing is common, targeted fishes likely react to divers very differently than in areas where fishing does not occur. The CRED fish team specializes in conducting Stationary Point Count (SPC) visual fish surveys, which have always been conducted on open circuit scuba. But what effect do the noisy, conspicuous bubbles produced by scientific divers using scuba have on our fish counts and biomass estimates? By using closed circuit rebreathers we can replace the blaring bubble machines with silent divers.

Diving on closed circuit rebreather, Kosta Stamoulis encounters a manta ray (Manta birostris) while conducting a Stationary Point Count visual fish surveys

Diving on closed circuit rebreather, Kosta Stamoulis encounters a manta ray (Manta birostris) during a SPC visual fish survey.

So that’s where the “bionic frogmen” come in. On the recently completed research cruise, CRED and partners conducted stationary point count visual fish surveys throughout the main Hawaiian Islands using both open circuit scuba and closed circuit rebreathers to compare results. Would we record more fish when using the less obtrusive rebreathers? Would we see more of the fish species targeted by fisheries when using rebreathers and the same amount of other smaller non-fished species like butterflyfish and damselfish? Surely we’d see the same number of hawkfish, those small wary fish perched on top of coral heads. Right? Well, we are only about halfway through our comparison study so it’s too early to say just yet, but preliminary results suggest that we are seeing some differences when using rebreathers and not always what we expected. We hope to work up the results in a scientific paper later this year.

Ray Boland meticulously preps his Inspiration rebreather prior to conducting an SPC survey.

Ray Boland meticulously preps his Inspiration rebreather prior to conducting an SPC survey.

If open circuit diving is so obtrusive, why don’t all scientific divers switch to using rebreathers? Because there are some disadvantages to diving with rebreathers which can make life difficult when conducting hundreds or thousands of surveys each year. For one, rebreathers are heavy and bulky, even for me, a 190-pound 6’2” guy. After coercing your body into the 65-pound rebreather and clipping on another 15-pound bailout tank, regular scuba gear feels like floating on a fistful of helium balloons. You also have to deal with much longer setup and breakdown times, more pre-dive preparation and buddy checks, and significantly more expensive gear and consumables. Rather than have everyone switch to rebreather, we are more interested in understanding any differences in fish biomass between open circuit scuba surveys and rebreather surveys. For now, rebreathers are another interesting tool we can use to help monitor and assess reef fish populations around the Hawaiian Islands and U.S. territories in the Pacific Ocean.

Posted in Coral Reef Ecosystem Division (CRED) | Tagged , , , , , , , , , , , , , , , ,

Where are all the Ranina ranina?

Where are all the Ranina ranina?

By guest blogger Lauren Van Heukelem

One main objective of the SE1503 cruise aboard NOAA ship Oscar Elton Sette was to survey the Commonwealth of the Northern Mariana Islands (CNMI) for Ranina ranina (Kona crab or spanner crab) that have been rumored to exist in the archipelago. This species is widely distributed across the Pacific and Indian Oceans in sandy-bottom habitats. It is an edible crab that generally supports sustainable, small-scale fisheries where it is found in abundance. Considering the depth and remoteness of some of the soft-bottom areas in the Marianas Archipelago, there is lack of information on this species yet strong local science partner interest in better understanding the potential distribution and abundance of this species in the area. Such a project was put forth at the “Marianas Trench Marine National Monument and Mariana Archipelago Ecosystem Science Implementation Plan Workshop” that was held in Saipan in May of 2013, and was subsequently chosen by the PIFSC to complete using a research team from the NOAA ship Oscar Elton Sette. The project was originally slated for 2014 but was postponed to 2015 due to scheduling delays. This served as one of the several primary objectives of project SE1503 over 11-27 June 2015.

All SE1503 Kona crab surveying efforts were undertaken by the crew of PIFSC small boat called SteelToe (SE6) and later after mechanical issues the Sette small boat called SE4. Both small boats were deployed off the Oscar Elton Sette nearly every day of the project with the exception of the days that we traveled between islands (Photo 1). Operations onboard SE6 began every morning at 7:30am with a small boat meeting and ended at 16:30 each evening, just in time for dinner. The crew consisted of our SE6 coxswain and SE1503 Small Boat Logistics Lead Jamie Barlow and deck crewmember Tony Flores. The remaining crew rotated between the scientists of SE1503 taking turns being data recorders and deck helpers throughout the cruise. The primary helpers were Lauren Van Heukelem, Erin Kawamoto, and Eric Cruz, but nearly all the SE1503 scientific staff and some Sette staff did a stint on SE6 or SE4 during the mission.

The surveys consisted of throwing eight sardine-baited ring nets attached to a 300ft ground line in sandy areas, considered to be optimal habitat for Ranina ranina, based on maps created for this cruise (Photo 2, 3, and 4). An example map is shown down below for Sarigan, where our spatially-balanced random point trapping survey locations are shown. These stations are located on prospective soft-bottom habitats and represented the starting points for our survey as we worked our way through the archipelago. We came outfitted with a large set of poster-sized charts for the science party to examine and mull over for the following day of operations, and we also shared a copy with the ship’s bridge. Much thanks to the PIFSC Mapping, GIS, and Graphics staff for generating these products for our project. These survey locations were located at a range of depths up to ~125m. The gear was left for a soak time between 30-60 minutes and then retrieved. Species were recorded upon coming up in each of the eight ring nets. Predation by sharks and other species was also recorded based on condition of bait and nets (Photo 5). We were also able to deploy a camera attached to one of our baited ring nets and view predation events occurring during the net soak time. This particular trap had five sharks fighting over the bait (photo 6). We also took some bottom grab samples to help validate the habitat mapping.

Unfortunately we were unable to confirm that Ranina ranina was present in the CNMI. Seven islands were surveyed (Uracus, Maug, Agrihan, Pagan, Alamagan, Guguan, and Sarigan) using a total of 101 ground lines with 808 nets deployed in various depths and no Ranina ranina were recorded. Although we were unable to locate Ranina ranina during our surveys, this does serve as a useful set of data points towards a better delineation of the distribution and abundance of this species across its range. During the course of the survey we were also able to assist in collecting samples for our fellow scientist Allison Miller when invertebrates came up in our ring nets. This allowed her to sample not only the nearshore ecosystems but also in deeper areas for her genetics study.


Photo 1: SE 6 arriving back at the Oscar Sette after a day of surveying.


Photo 2: Sardine baited ring nets used for Ranina ranina capture.


Photo 3: Tony Flores and Lauren Van Heukelem preparing to deploy a set of eight ring nets attached to a 300ft ground line.


Photo 4: Jamie Barlow getting us in position while the crew prepares the nets.


Photo 5: Jamie Barlow bring up a ring net that had had the bait removed by a predator.


Photo 6: Video screenshot of shark removing bait from a ring net.


Map 1: Example map of Sarigan and our spatially-balanced random point trapping survey design targeting prospective soft-bottom habitats in the depth range 0-125m.

Posted in Ecosystems and Oceanography Division (EOD), Scientific Operations

SE1503 – Sharks on the Ship and Videos from the Deep

By Guest Bloggers Cassie Pardee and Diona Drake

Here we present another update from project SE1503 aboard NOAA ship Oscar Elton Sette performing fisheries oceanographic research in the Mariana Islands (11-27 June 2015).

We have been trapping from the Sette with lobster pots, minnow traps, and a BIG trap around most of the archipelago, to supplement the trapping survey being done by the small boat team. Each morning we are never sure what we are going to pull out of the water. We are targeting relatively deep 50-125m soft-bottom areas using the best available mapping information, ship sounders, as well as a small Ponar bottom grab to assist in placing our gear in those areas with unconsolidated substrate (http://youtu.be/gfJqcSpTOSQ). Surprisingly, we are bringing up a more than a few sharks. We are surprised because the small openings in our traps would have seemed to be an effective deterrent to shark bycatch. The most common species being captured include white tip reef sharks (Triaenodon obesus), gray reef sharks (Carcharhinus amblyrynchos), and nurse sharks (Ginglymostoma cirratum). The gray reef and nurse sharks have all been brought up in the giant fish trap (Figure 1). Some of the sharks are so wide, we can hardly believe that they could fit through the trap opening. The white tip reef sharks really love the little, black lobster pots which have even smaller openings and less space. We have even brought up two sharks in one pot a few times (Figure 2), and once three white tips were jammed into a single lobster pot. All of the sharks are released alive once they have been quickly measured, photographed, and two non-invasive fin clips are taken from their dorsal fins for genetic analysis (Figure 3).

During our daytime BIG trap deployment we have been attaching GoPro and FlyWire cameras to the outside and the inside of the trap to see bottom type and what is really going on after we lose sight of the trap. The video footage has been very revealing. Sometimes we will bring up an empty trap and then watch video footage to see fish swim in and then back out of the trap, or watch as sharks and sting rays try repeatedly to enter the trap but are too big to fit through the opening. We have captured video images of garden eels (http://youtu.be/BuJmBKAVRO4), tiger sharks (https://youtu.be/HnirPxNu-Fk), huge sting rays (https://youtu.be/0Vh-oCiaqlU), giant hermit crabs (http://youtu.be/IxxN3InCGgQ), schools of juvenile fishes (https://youtu.be/3s_zIJvuWh0), and various other fish species (some cunning enough to swim in and out of the trap). The video footage exposes a whole new aspect to how the trapping process works and gives us the opportunity to see other species in the area that were too smart (or too big or too small) to get caught in our traps. We also tried collecting some video during the night (http://youtu.be/YZpHLdxJ2zo). While our trapping work is part of a broader ecosystem survey, the findings will feed into a better understanding of how fishing gear operates. The mechanics of the capture process are often overlooked, yet are a key component of fishing gear efficiency and fishery stock assessments that rely on data from fishing gear.


Figure 1. Nurse shark and gray reef shark brought up in the BIG trap.


Figure 2. Two white tip reef sharks being released from a lobster pot.


Figure 3. A white tip reef shark being released after measurement and fin-clips.

Posted in Ecosystems and Oceanography Division (EOD), Scientific Operations

Successful Rose Atoll Marine National Monument and American Samoa Ecosystem and Fisheries Research Prioritization Workshop

Over 30 representatives from American Samoa including resource managers, scientists and local community members met for two days (May 26-27, 2015) in Utulei, American Samoa to share knowledge about past, current and future marine research in the American Samoa Archipelago. Seven sessions were held with 3-4 talks per session on topics related to fisheries, ecosystems, community involvement, understanding and addressing threats, and protected species.  The sessions included both presentations and discussions.

Participants of 2015 Rose Atoll Marine National Monument and American Samoa Ecosystem and Fisheries Research Workshop

Participants of 2015 Rose Atoll Marine National Monument and American Samoa Ecosystem and Fisheries Research Prioritization Workshop

Some of the highlights of the discussion included recommendations for:


  • Prioritize parrotfish life history analysis
  • Spawning aggregations and periods
  • Albacore density in American Samoa Exclusive Economic Zone and time of year
  • Bottomfish stock assessments
  • A lot of stock assessment and life history data are in the queue at PIFSC, but lacking manpower to get final results
  • Integration of different data: connectivity and fisheries data
Department of Marine and Wildlife Resources Biosampling team demonstrating how to extract an otolith from a fish and examining under microscope

American Samoa Government, Department of Marine and Wildlife Resources Biosampling team demonstrating how to extract an otolith from a fish and examining under microscope


  • Nearshore ocean current modeling
  • More work on nearshore connectivity
  • Understanding connectivity at a fairly fine scale
  • Identification of areas that are more resilient (climate change, etc.)
  • Looking at satellite data and productivity (ChlA, SST). Correlate with fishery data, monitoring data and connectivity survey.
  • Look at the environmental variables for the akule fishery
  • How do you engage and sustain community involvement? A. community visits every month. Schedule village meetings with the village mayors and chiefs on village councils.  Community outreach every quarter and annual village council meetings.
  • MPA performance evaluation “score card” (including socioeconomic, biological and institutional) is being developed for the AS system. There should also be some assessments of federally managed areas. This would be to address some of the fishermen’s concerns that maybe they weren’t completely included in the process or that some of the regulations are unfavorable to them.
  • Super Alias. Developing better boats that can go beyond the current measures (50 nm) will be a huge change. This will result in feeding the local folks and having the capability of exporting fish to Hawaii and the mainland. The Secretariat of the Pacific Community (SPC) is working on this, compare to PIFSC research (economically viable).
  • Need research on awareness of allowable and prohibited activities for MPAs. There are several types of MPAs in American Samoa, so getting input from people about their awareness in terms of what is allowed within MPAs.  Include this aspect in future research studies.
  • Continue to develop socioeconomic factors of communities, like where communities are getting their food. Is it from the ocean? Is it from the land?  Are they government dependent?
  • Marine Protected Areas – There is a data need for enforcement and compliance. How often is enforcement going on?  Are people actually complying with regulations?  Bio-monitoring is less meaningful without enforcement information.
  • The territory is relying heavily on imported goods. Is this because there aren’t enough fish to sustain our population?  Is the fish population declining?
  • Identify carrying capacity of Tutuila (population, water, etc.)

Understanding and Addressing Threats

  • More research into the juvenile Crown of Thorns starfish (COTs)
  • Genetic study of COTs
  • High pollution a contributing factor to coral reef degradation (littering, septic system issues, etc.)
  • Lack of COTs predators in American Samoa
  • More research into factors that contribute to coral bleaching (e.g. climate change, ocean acidification)
  • Climate change is primary contributing factor to coral bleaching.
  • Faga‘alu Bay has strong currents so the water circulation patterns likely affect where the nutrients are concentrated (northern side of Bay).
  • More research in Vatia and Pala Lagoon, looking at water quality, identifying pollution, and finding solutions to clean up the area.
  • Are there studies on active removal of coral anomalies / tumors? A. Research in Fagatele Bay – removed anomalies, where they were removed they didn’t come back, but they would still pop up elsewhere on coral.
  • Research on certain types of fish (herbivores, bottom feeders) – should we be protecting certain species more than others? Are there certain species that are more important in American Samoa?
  • Diseases in the system are natural. Reefs that are stressed are more likely to get disease, so keeping the reefs clean and healthy is a growing concern.
  • Understanding the life history of American Samoa reef fish would be helpful to better protect and make management decisions about herbivores that are important to reef resilience
  • Need field work that looks at local catch limits within the territorial waters. Fish size should be regulated because it hasn’t been done yet.  Fish size has been identified as a priority for the territory. Need collaboration with scientists on size limits.
  • American Samoa has a huge need for social science.
Workshop participants discussing community outreach and scientific collaborations during a public session

Workshop participants discussing community outreach and scientific collaborations during a public session

Protected Species

  • Critical habitat research needs to be done. Sand mining has been happening a lot lately, which affects nesting.
  • Severe lack of stock assessments of cetaceans for Odontocetes in this area. It isn’t easy to do logistically.  Upcoming cruises might want to try their best to consider setting up survey methods for that.  High incidents of false killer whale depredation, etc. with the long line fishery.
  • What is the timeline for mapping ESA-listed corals?
  • Longline fisheries have had quite a few incidents of silky shark interactions. This is a species of concern for SPC.  There may be an opportunity to explore more work while looking into shark populations in Samoa as well.
Dr. Bob Humphreys presenting on life history and biosampling in the Sunia Ocean Center, American Samoa

Dr. Bob Humphreys presenting on life history and biosampling in the Sunia Ocean Center, American Samoa


Discussions on potential research projects were initiated. A few examples of the top priorities include:

  • Perceptions of community on establishment of MPAs, MPA terms/types (allowed vs. prohibited activities), etc.
  • Species-specific connectivity studies (by genetics)
  • Disease and Contaminants: Follow-up on Witall studies on landfill inputs into nearshore marine environment (especially Fagatele Bay nearby Futiga landfill)
  • Shallow near-shore marine environment mapping (using LiDAR data)
  • Determine locations, seasons and periods of spawning aggregations
  • Study ocean current models for connectivity studies
  • More contaminant and nutrient work in Vatia (1) H2O quality/LBSP; (2) Management Plan
  • Coral bleaching adaptation responses, find resistant/ resilient colonies or areas
  • More research on juvenile COTS (where are they and when they recruit to reefs)
  • Understanding factors that make a successful MPA (seeding / spillover) biological and socioeconomic
  • What is the carrying capacity of the island? Especially related to landfills and clean water?

Next steps include posting an abridged workshop report summary on our PIFSC internet site with links to all of the speaker presentations. We expect to have a full workshop report draft to share for review by early August with the final expected to be put through our final PIFSC publication review by end of September, 2015.

For more information about other activities from the PIFSC Science Operations Division, browse recent blog posts.







Posted in Coral Reef Ecosystem Division (CRED), Ecosystems and Oceanography Division (EOD), Fisheries Research and Monitoring Division (FRMD), Protected Species Division (PSD), Scientific Operations, Socioeconomics Program | Tagged , , , , , , , , , , , , , , , , , ,

Counting Fish: Bubbles or Not? Expedition underway to assess reef fish populations in the Main Hawaiian Islands

From June 14 to July 3, 2015, the NOAA Ship Hi‘ialakai will be the platform for a research cruise to gather data and improve assessments of the status of coral reef fish populations in the main Hawaiian Islands. Led by project leader, Kevin Lino, and lead scientist, Ivor Williams, of the NOAA PIFSC Coral Reef Ecosystem Division (CRED), the cruise is a multi-agency effort, involving participants from the Papahānaumokuākea Marine National Monument, State of Hawai‘i Division of Aquatic Resources, and the University of Hawai‘i.

A school of unicornfish (Naso unicornis) swarm in the coral reefs off the coast of Maui. NOAA photo by Kevin Lino.

A school of unicornfish (Naso unicornis) swarm in the coral reefs off the coast of Maui. NOAA photo by Kevin Lino.

During the 20-day expedition, scientists plan to conduct approximately 300 underwater visual surveys of reef fishes and habitat, with sites spread widely across coral reef areas in all of the populated Hawaiian Islands, from the Big Island of Hawai‘i to Ni‘ihau. The survey methods and sampling design used for the cruise are consistent with those implemented for NOAA’s existing long-term coral reef monitoring program in the U.S. Pacific, which allows multiple data sets to be readily combined and easily compared.

Scientists survey fish populations using the "Stationary Point Count" method, in which pairs of divers record the number, size, and species of all fishes observed within adjacent visually estimated cylinders 15 meters in diameter. NOAA photo by Paula Ayotte.

Scientists survey fish populations using the “Stationary Point Count” method, in which pairs of divers record the number, size, and species of all fishes observed within adjacent visually estimated cylinders 15 meters in diameter. NOAA photo by Paula Ayotte.

These survey efforts are primarily designed to improve the ability of PIFSC and partners to generate an accurate picture of the status and trends of coral reef fishes around the Hawaiian Islands, but because the overall dataset is highly consistent and widely representative of reef areas across the region, it is suitable for multiple purposes and is being increasingly used for large-scale scientific research by NOAA and external researchers.

Divers conduct surveys from small boats launched from the NOAA Ship Hiʻialakai.

Divers conduct surveys from small boats launched from the NOAA Ship Hiʻialakai.

One project that will be investigated during the cruise will be to compare fish counts gathered by divers on closed-circuit rebreather (CCR) with fish counts by divers using SCUBA. Because divers on CCR do not produce bubbles, they are much quieter and a less intrusive presence in the marine environment. Therefore, it is possible that use of CCR may enable divers to get better information on marine species that are wary of divers.

As with all data collected by NOAA, any information gathered during the cruise will be available on request. All coral reef survey data sets, compiled and analyzed by CRED staff and project partners, are routinely reported in post-cruise monitoring briefs and annual data reports.

Posted in Coral Reef Ecosystem Division (CRED) | Tagged , , , , , , , , , , , , , , , ,

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.


Photo 1: Open lobster traps waiting to be baited


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


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


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


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.



Figure 1: Our “BIG” trap.


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


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.


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


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


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

Posted in Ecosystems and Oceanography Division (EOD), Scientific Operations