Variations in the Amount of Macroplankton by Day and Night

Abstract

1. Twenty oblique hauls of a stramin ring-trawl, diameter of mouth 5 feet, were made during a period of 48 hours off Liverpool, Nova Scotia, i n May, 1932.2. The common species were Thysanoëssa mschii, Th. inermis, Sagilta elegans, Calanus finmarchicus and C. hyperboreus.3. All of the above occurred in the collections made during the night n i larger numbers than in those in the daytime. No such discrepancy appeared in the case of the Fish Ova.4. The discrepancy is held to be due in each case to a proportion of the population sinking to depths greater than could be sampled by the net.