Electronic Tagging of Green Sturgeon Reveals Population Structure and Movement among Estuaries

Abstract

Green sturgeon Acipenser medirostris spend much of their lives outside of their natal rivers, but the details of their migrations and habitat use are poorly known, which limits our understanding of how this species might be affected by human activities and habitat degradation. We tagged 355 green sturgeon with acoustic transmitters on their spawning grounds and in known nonspawning aggregation sites and examined their movement among these sites and other potentially important locations using automated data-logging hydrophones. We found that green sturgeon inhabit a number of estuarine and coastal sites over the summer, including the Columbia River estuary, Willapa Bay, Grays Harbor, and the estuaries of certain smaller rivers in Oregon, especially the Umpqua River estuary. Green sturgeon from different natal rivers exhibited different patterns of habitat use; most notably, San Francisco Bay was used only by Sacramento River fish, while the Umpqua River estuary was used mostly by fish from the Klamath and Rogue rivers. Earlier work, based on analysis of microsatellite markers, suggested that the Columbia River mixed stock was mainly composed of fish from the Sacramento River, but our results indicate that fish from the Rogue and Klamath River populations frequently use the Columbia River as well. We also found evidence for the existence of migratory contingents within spawning populations. Our findings have significant implications for the management of the threatened Sacramento River population of green sturgeon, which migrates to inland waters outside of California where anthropogenic impacts, including fisheries bycatch and water pollution, may be a concern. Our results also illustrate the utility of acoustic tracking to elucidate the migratory behavior of animals that are otherwise difficult to observe.

Received April 14, 2010; accepted November 14, 2010

ACKNOWLEDGMENTS

This research was supported by the NOAA–Fisheries Species of Concern Program (S.T.L. and M.L.M.), the Northwest Fisheries Science Center internal grants program, the Wildlife Conservation Society, and the David and Lucile Packard Foundation (D.L.E.), and the CALFED Science Program (P.K., J.T., and J.H.). Numerous people helped in the field, including M. Howell, S. West, E. Evans, C. Black, B. Pickering, D. Farrer, and B. Cady (Washington Department of Fish and Wildlife); J. Weber, B. Krohn, G. Ryden, and C. Barber (Oregon Department of Fish and Wildlife); K. Hanson and A. Keller (Wildlife Conservation Society); R. Whitlock (Imperial College, UK); M. Webb, K. Kapperman, J. Ogawa, and G. Stutzer (U.S. Fish and Wildlife Service); S. Turo and R. Benson, (Yurok Tribal Fisheries); H. Fish, D. Rundio, A. Ammann, and J. Harding (NOAA Southwest Fisheries Science Center); and G. Holt and E. Danner (University of California at Santa Cruz). The Columbia River Intertribal Fish Commission (D. Hatch and R. Branstetter) and the Oregon Department of Fish and Wildlife (D. Hering) provided hydrophone data from the Columbia River estuary. K. Andrews (NOAA Northwest Fisheries Science Center) supplied detection data for Puget Sound. J. Power (U.S. Environmental Protection Agency, Hatfield Marine Science Center) provided data from receivers in the Alsea River and Yaquina Bay. D. Rundio conducted the similarity profile analysis of the migration history dissimilarity matrix. S. X. Cadrin, E. Mora, C. Grimes, W. Perrin, and two anonymous reviewers provided helpful reviews of an earlier draft of the manuscript.

Notes

^aHS = highly stratified; MS = moderately stratified; VH = vertically homogeneous.

^bIncludes San Pablo and Suisun bays.