Abundance of mesozooplankton in the North Balearic Sea in April 2003

Mouth diameter of the net was 113 cm, mesh size 200 µm. Each sample was split in two aliquots; an aliquot (ranging from 50 to 100%) was immediately fixed with formaldehyde (2-4% final concentration) for specimen identification and counts, while the other aliquot was maintained fresh and immediately utilized for biomass measurements. Volumes of filtered seawater were estimated by multiplying the area of the net mouth by heights of sampled layers from winch readings. Identification and counts of specimens were performed on aliquots (1/20-1/40) of the fixed samples by using a graduate large-bore pipette. Copepods were identified to the species level and separated into females, males and juveniles (copepodites). All other taxa were identified at the species level when possible, or at higher taxonomic levels. Taxonomic identification was done according to the most relevant and updated taxonomic literature.