Different gear, different samples

During this cruise we have been using primarily three types of gear to collect plankton samples: a 61-cm bongo net, 1.8-m Isaacs-Kidd midwater trawl (IKMT), and a Video Plankton Recorder (VPR). The bongo and IKMT are pulled through the water and plankton is concentrated at the tail end of the net, also called the cod end.

Two sample jars

Samples collected from the same station using different gear. On the left is a sample collected with a 61-cm bongo net that has lots of small copepods. At right is a sample collected from the 1.8-m IKMT with larger crustaceans and very few copepods. (Photo by Harvey Walsh, NEFSC/NOAA)

Due to different mouth opening and mesh size, bongo and IKMT collect different amounts of plankton, different types of plankton, and different sizes of plankton from the same station. The bongo has a smaller mouth opening and finer mesh than the IKMT, and generally catches smaller zooplankton and fish larvae. The IKMT is more efficient at collecting larger zooplankton and fish.

Various plankton from the IKMT

Plankton collected with the Isaacs-Kidd midwater trawl (IKMT): krill (A), eel leptocephalus (B), lanternfish (C), silver hake (D), and (E) windowpane flounder. (Photos by Chris Melrose, NEFSC/NOAA)

four images captured by the VPR

Images captured by the Video Plankton Recorder (VPR): comb jelly (A), krill (B), Atlantic herring larvae (C), and copepod (D).

Using multiple types of nets or advanced sampling instruments to collect plankton information on a cruise allows researchers to better understand the entire plankton community.

Harvey Walsh
Chief Scientist
DE 11-10 Ecosystem Processes Research Cruise

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