(1) Development of measuring system for jellyfish by VPR
Fish are sampled by a net in general; however, the very fragile organisms, such as jellyfish, are easily broken in a net. Visual Plankton Recorder (VPR) provides a solution to this problem. A stroboscopic camera is towed just like a net to take pictures of such organisms. This enables us to estimate number and size of the organisms without net samplings. Recently, VPR was improved by using a camera equipped with a wide-field lens, and the best shooting conditions were selected for almost transparent jellyfish. Amazingly, recent applications of the update VPR suggested that from 10- to 100-fold more jellyfish are distributed in the mid- and deep-sea ecosystems than expected before based on net samplings.
VPR system and its application. (a) Main body of VPR; (b) and (c) Pictures of jellyfish taken by VPR; (d) Comparison of density estimates between VPR and MOCNESS.
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