Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

35.  EXPERIMENTAL STUDIES OF PALLID STURGEON DISPERSAL AND VERTICAL SWIMMING HEIGHT DURING ONTOGENY

Boyd Kynard*, S.O. Conte Anadromous Fish Research Center, Box 796, Turners Falls, MA 01376: Phone 413-863-3807; FAX 413-863-9810; kynard@forwild.umass.edu

Erika Parker, S.O. Conte Anadromous Fish Research Center, Box 796, Turners Falls, MA 01376: Phone 413-863-3830; FAX 413-863-9810; henyey@forwild.umass.edu 

Don Pugh, S.O. Conte Anadromous Fish Research Center, Box 796, Turners Falls, MA 01376: Phone 413-863-3832; FAX 413-863-9810; pugh@usgs.gov

Tim Parker, S.O. Conte Anadromous Fish Research Center, Box 796, Turners Falls, MA 01376: Phone 413-863-3830; FAX 413-863-9810; henyey@forwild.umass.edu

We observed dispersal of pallid sturgeon hatchling free embryo to early-larva life intervals in three water velocity treatments (mean velocity =17.3, 21.1, and 30.1 cm/s).  Water current determined movement pattern of free embryos, carrying them around all test tanks like passive particles until they entered an eddy.  After entering an eddy, the constant swim-up and drift behavior eventually returned embryos to channel flow.  Some late embryos began holding position on day 8 in the slow and moderate velocity treatments, but no embryo or larvae (fish day 12 or older) could hold position in the fast velocity treatment.  Dispersal duration was 12–13 days in slow or moderate velocity treatments, so water velocity had no effect on dispersal duration.  Swimming height of days 0–5 early-embryos (to CTU= 83.5) was < 50 cm, but in a 300 cm deep swim tube, days 6–11 late-embryos (to CTU= < 200), dispersed throughout the water column, and on some days, swam higher in the day than at night.  As fish developed into larvae at CTU >200 (day 12) and began to forage, most larvae became benthic with 75–80 % preferring to swim < 50 cm above the bottom.  Thus, swimming height switched once within the free embryo life interval, then switched again when fish developed into larvae.  This is the first occurrence yet found in sturgeons of a switch in swimming height within the free embryo life interval.  Late embryos tested for swimming height at 150 cm and at 300 cm water depths swam closer to the water surface in 150 cm deep water, suggesting fish can detect water pressure, and during dispersal, adjust swimming height depending on water depth.  Cumulative temperature degree-days (CTU) is the link between dispersal behavior of these fish and river water temperature.  Modeling of pallid sturgeon dispersal speed should be done separately for early embryo, late embryo, and early-larva life stages.  The results suggest the following for modeling dispersal speed: for early embryos (0–83.5 CTU) – use water velocity < 50 cm above the bottom; for late embryos (CTU=84–200) – use mean column velocity; and for early larvae (CTU= 200–240) use velocity < 50 cm above the bottom.