M2 AM Aquatic Ecotoxicology (Part 1)
Monday, 14 November 2005: 8:00 AM - 11:40 AM in Ballroom 2

(OST-1117-767634) Striped bass habitat use in the San Francisco estuary determined using otolith microchemistry techniques.

Ostrach, D¹, Phillis, C², Weber, P³, Ingram, B², Zinkl, J¹, ¹ University of California at Davis, Davis, CA, USA² University of California at Berkeley, Berkeley, CA, USA³ Lawrence Livermore Laboratory, Livermore, CA, USA

ABSTRACT- Habitat use has been shown to be an important factor in the bioaccumulation of contaminants in striped bass. This study examines migration in striped bass as part of a larger study investigating maternal transfer of xenobiotics to progeny in the San Francisco Estuary. Habitat use, residence time and spawning migration over the life of females was studied (n = 50). Female striped bass were collected on the Sacramento River during the spawning runs of 1999-2001. Additonal samples were obtained during the 2005 spawning season from the San Joaquin River and nearshore Pacific Ocean. Otoliths were removed, processed and aged via otolith microstructure. Subsequently, otoliths were analyzed for strontium/calcium (Sr/Ca) ratio using an electron-microprobe to measure salinity exposure thus distinguishing freshwater, estuary, and marine habitat use. In addition, a subset of otoliths were subjected to LA-ICPMS and MC-LA-ICPMS techniques to verify electron probe findings and to gain additional elemental and isotopic data in order to refine temporal and spatial habitat use. Salinity exposure during the last year before capture was examined more closely for comparison of habitat use by the maternal parent to contaminant burden transferred to progeny. The Sr/Ca data demonstrate a wide range of migratory patterns. Age of initial ocean entry differs among individuals before returning to freshwater, presumably to spawn. Some fish reside in freshwater year-round, while others return to more saline habitats and make periodic migrations to freshwater. Frequency of habitat shifts and residence times differs among fish, as well as over the lifetime of individual fish. However, not all fish migrated to freshwater to spawn in the previous year. Results from this investigation will be combined with contaminant and histological developmental analyses to better understand the bioaccumulation of contaminants and the effects they and habitat use have on fish populations in the San Francisco Estuary.

Key words: otolith sr/ca, striped bass migration, habitat use, otolith microchemistry techniques