Blog 4 – The Giant Net

Our research vessel has officially become a 24-hour research marathon! No moment is wasted on R/V Melville. There is a coordinated schedule to allow every scientist on board to collect samples or data. Some scientists work only at night or only during the day. Others work throughout the day and night depending on the length of their research activities. All work is done in cycles, which means that the collection of data lasts three to four days at a time.

The reason for this length of time has to do with the selection of a parcel of water that we follow using drifters. Drifters or buoys travel in the direction of a mass of water and we follow their path by the signals they send to our computers by satellite. We are interested in the interactions that occur in one specific part of the ocean at a time.

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Amanda Netburn, a Scripps Ph.D. student, and Jami Chang prepare the Oozeki net for deployment. Some of the trawls are done during the night to collect samples of night feeders.

My first assignment on this experimental cycle was to assist with the Oozeki net mid-water trawl led by Amanda Netburn, a Scripps Ph.D. student. Amanda’s research is awesome! She studies how different species of fish respond to changes in their environment such as warmer temperatures and lower concentrations of oxygen (hypoxic layer). She is especially interested in studying organisms in the mesopelagic layer, which is an ocean layer between 200-1,000 meters (656-3,280 feet) of depth.

To do this, she collects samples of lantern fish at a depth of around 200 meters (656 feet). As we lowered the Oozeki net into the water I imagined it was a giant butterfly net immersed into the ocean to collect fish!

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Dr. Pete Davison, Amanda Netburn, and Jami Chang with a retrieved net.

Using the Oozeki net for Netburn’s research is appropriate because it is designed to catch larger, faster animals that can swim (nekton) in contrast to animals that are free-drifting, such as plankton. Lantern fish are very interesting because they tend to live in the depths of the ocean and travel to the mesopelagic layer to feed at night. They hide in the deep waters in the daytime to protect themselves from predators that are able to see them with the penetrating sunlight in surface waters.

Dr. Pete Davison is also interested in studying lantern fish. He gathers data from a sonar that sends sound waves to the bottom of the ocean. These acoustic waves bounce back creating a sonar picture of the seafloor. But the acoustic waves also reflect off fish and plankton in midwater, where they form “deep scattering layers.”

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This is a lantern fish with a parasitic copepod attached to it.

These scattering layers tell scientists where the concentrations of life in the ocean are located. By measuring the fish we find in the nets, Pete is able to confirm the accuracy of the acoustic data.

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This is a pyrosome.