Quantitative Assessment of the Vertical Distributions of Micronektonic Fishes with Opening/Closing Midwater Trawls

AbstractSome problems of sampling oceanic micronekton with midwater trawls, especially those with opening/closing devices, are reviewed. Contamination of the catches is a major problem with codend opening/closing devices. Avoidance and escapement are perennial problems with small nets typically used by oceanographers. In order to capture the full spectrum of mesopelagic fishes, including agile or large ones, large nets as well as small nets are needed. Large trawls are not practical to use from most research ships, and the volume of water filtered is difficult to measure.