Effects of nutritional deprivation on juvenile green sturgeon growth and thermal tolerance

Environ Biol Fish (2015) 99:145–159 DOI 10.1007/s10641-015-0463-8 Effects of nutritional deprivation on juvenile green sturgeon growth and thermal tolerance Christine E. Verhille & Seunghyung Lee & Anne E. Todgham & Dennis E. Cocherell & Silas S. O. Hung & Nann A. Fangue Received: 3 February 2015 / Accepted: 9 November 2015 / Published online: 19 November 2015 # Springer Science+Business Media Dordrecht 2015 Keywords Green sturgeon . Nutrition . Temperature . HSP70 . CTmax . Growth Introduction In the San Francisco Estuary (SFE), declines in the abundance of native fish species have been linked to altered food webs and reduced food availability (Moyle 2002; Feyrer et al. 2003; Kimmerer 2004). This is particularly concerning for protected green sturgeon (Acipenser medirostris Ayres, 1854) populations re- stricted to the SFE during early life stages. Green stur- geon are composed of at least two genetically distinct and protected populations (Israel et al. 2009): the North- ern and Southern Distinct Population Segments (DPS), and spawn only in Oregon and California, USA. Details of the current distribution and spawning locations of these fish can be found in Beamesderfer et al. (2007). Briefly, anadromous adult green sturgeon spend most of their lives in the marine environment, with seasonal migrations between natal freshwater spawning grounds C. E. Verhille : D. E. Cocherell : N. A. Fangue (*) Department of Wildlife, Fish and Conservation Biology, University of California, One Shields Avenue, Davis, CA 95616, USA e-mail: nafangue@ucdavis.edu S. Lee : A. E. Todgham : S. S. O. Hung Department of Animal Science, University of California, One Shields Avenue, Davis, CA 95616, USA and the ocean. Adults of the Northern DPS, which is classified as a species of concern by the National Oce- anic and Atmospheric Administration (NOAA) of the USA, spawn in rivers north of the Eel River of north- west California (Adams et al. 2007). The Southern DPS is classified as threatened under the Endangered Species Act, and all suspected and confirmed spawning loca- tions are within the watershed of the Sacramento and San Joaquin rivers (Adams et al. 2007). As juvenile green sturgeon are intolerant of full strength seawater until they are 0.5 to 1.5 years old (Allen and Cech 2007; Allen et al. 2009, 2011), habitat is restricted to the fresh to brackish water sections of the SFE for early life stages. The SFE is made up of two major Californian rivers, the Sacramento and San Joaquin, and their drainage to the Pacific Ocean through the San Francisco Bay. Since the 1800’s, this watershed has been highly modified through hydraulic gold mining in the Sierra Nevada mountains, followed by consumption and diversion of water to support urbanization and agriculture, introduc- tion of sewage input, and active management through environmental policy (Atwater et al. 1979; Cloern and Jassby 2012). International shipping, climate change and ecosystem alterations have created conditions con- ducive to pervasive invasions by non-native species, which now characterize the entire system (Atwater et al. 1979; Cloern and Jassby 2012). These ecosystem-wide changes are directly attributable to pop- ulation declines of native aquatic biota associated with all trophic levels (Cloern and Jassby 2012), resulting in large shifts in the composition of biological