Data for Comparison of Size, Terminal Fall Velocity, and Density of Bighead, Silver, and Grass Carp Eggs for use in Drift Modeling

Abstract

Invasive Asian carps established in the United States spawn in turbulent water of rivers and their eggs and early larvae develop while drifting in the current. The eggs are slightly denser than water and are held in suspension by water turbulence. The eggs are believed to perish if they settle before hatching. It is thus possible to use egg drift modeling to assess the capability of a river to support survival of Asian carp eggs. Data to populate such models include the physical properties of the assessed rivers, and information on egg size, density, and terminal fall velocity (sinking rates). Herein, we present the physical characteristics of the eggs as a function of post fertilization time. We recorded mean egg diameter and terminal fall velocity for eggs from each species during the first five hours of development, and at approximately 12 and 22 hours post fertilization. Eggs of all species reached their maximum size before 4 hours. Water-hardened Silver Carp Hypophathalmicthys molitrix and Grass Carp Ctenopharyngodon idella eggs were similarly sized in our trials, and Bighead Carp Hypophathalmichthys nobilis water-hardened eggs were the largest. After water hardening, Silver Carp eggs sank slowest and Bighead Carp eggs sank fastest. For a given species, smaller diameter eggs generally had faster terminal velocity and had higher specific gravity than larger eggs. These data were used to develop a regression growth model of eggs of three species of Asian carp, which includes time-dependent relations for density and diameter of eggs. Asian carp growth models used in conjunction with egg drifting models provide insights regarding the potential of a river to transport Asian carp eggs in suspension until hatching.