Monthly mesoozooplankton samplings started in 1950s, performed by vertical tows of Hensen net (73 cm mouth diameter, 330 µm mesh size) from 35–0 m. Samples were fixed in 2 % formaldehyde solution buffered with borax. No flowmeter was used. From 1950s-1995 mesozooplankton was sampled on approximately monthly basis and data are available from January 1972 to November 1995 (with gaps in 1975) and include the abundances expressed as no.ind.m-3 at group level of the zooplankton groups such as Copepoda, Cladocera, Appendicularia, Chaetognatha, Tunicata, Ostracoda, Polychaeta, Decapoda larvae, various meroplankton larvae, Pisces ova, Pisces larvae and Hydromedusae/Siphonophora. From 1995 the sampling program with Hensen net was interrupted and investigations continued with Nansen net, 125 µm mesh size.