A new method to measure the terminal velocity of small particles: A demonstration using ascending eggs of the Atlantic menhaden (Brevoortia tyrannus)

A new method, incorporating video, motion analysis, and a novel experimenta l apparatus, was used to measure the terminal velocity of particles. The me thod facilitated the investigation of treatment effects and maximized the n umber of measurements for each replicate, thus improving the statistics for a population of particles. The eggs of the Atlantic menhaden (Brevoortia t yrannus) were used to demonstrate the method by investigating the effects o f salinity and stage of development on their ascent rate. Egg ascent rate w as greatest at intermediate salinity (36.5 parts per thousand) and decrease d in the late stage of embryonic development. We estimate eggs at oceanic s alinities (>35.5 parts per thousand) in nature to ascend at 0.19-0.25 cm s( -1).