Population Dynamics and Distribution Patterns of Longfin Smelt in the San Francisco Estuary

Rosenfield, Jonathan A.; Baxter, Randall D.

doi:10.1577/t06-148.1

Cited by 48 publications

(89 citation statements)

References 26 publications

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“…Examination at multiple levels of biological organization (cellular to wholeorganism) highlighted the potential vulnerability of longfin smelt relative to delta smelt. Longfin smelt aggregate in deeper water during peak seasonal temperatures, potentially to avoid extreme surface temperatures (Rosenfield and Baxter, 2007). Therefore, longfin smelt may respond behaviorally by seeking out suitable temperatures.…”

Section: Discussionmentioning

confidence: 99%

Effects of high temperatures on threatened estuarine fishes during periods of extreme drought

Jeffries

Connon

Davis

et al. 2016

Journal of Experimental Biology

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Climate change and associated increases in water temperatures may impact physiological performance in ectotherms and exacerbate endangered species declines. We used an integrative approach to assess the impact of elevated water temperature on two fishes of immediate conservation concern in a large estuary system, the threatened longfin smelt (Spirinchus thaleichthys) and endangered delta smelt (Hypomesus transpacificus). Abundances have reached record lows in California, USA, and these populations are at imminent risk of extirpation. California is currently impacted by a severe drought, resulting in high water temperatures, conditions that will become more common as a result of climate change. We exposed fish to environmentally relevant temperatures (14°C and 20°C) and used RNA sequencing to examine the transcriptome-wide responses to elevated water temperature in both species. Consistent with having a lower temperature tolerance, longfin smelt exhibited a pronounced cellular stress response, with an upregulation of heat shock proteins, after exposure to 20°C that was not observed in delta smelt. We detected an increase in metabolic rate in delta smelt at 20°C and increased expression of genes involved in metabolic processes and protein synthesis, patterns not observed in longfin smelt. Through examination of responses across multiple levels of biological organization, and by linking these responses to habitat distributions in the wild, we demonstrate that longfin smelt may be more susceptible than delta smelt to increases in temperatures, and they have little room to tolerate future warming in California. Understanding the species-specific physiological responses of sensitive species to environmental stressors is crucial for conservation efforts and managing aquatic systems globally.

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Section: Discussionmentioning

confidence: 99%

Effects of high temperatures on threatened estuarine fishes during periods of extreme drought

Jeffries

Connon

Davis

et al. 2016

Journal of Experimental Biology

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“…In the winter (December to April), prespawning delta smelt migrate to tidal freshwater habitats for spawning, and larvae rear in these areas before emigrating down to brackish water (Bennett 2005). Adult longfin smelt may also migrate into the Delta during the winter for spawning, generally moving up from San Francisco Bay or the Pacific Ocean (Rosenfield and Baxter 2007). Longfin smelt are native to the Pacific coast and generally spawn in brackish and freshwater of the estuary when 2 years old (Rosenfield and Baxter 2007), although some will live for up to 3 years (Moyle 2002).…”

Section: Life History Traits Of the Fishes Examinedmentioning

confidence: 99%

“…Adult longfin smelt may also migrate into the Delta during the winter for spawning, generally moving up from San Francisco Bay or the Pacific Ocean (Rosenfield and Baxter 2007). Longfin smelt are native to the Pacific coast and generally spawn in brackish and freshwater of the estuary when 2 years old (Rosenfield and Baxter 2007), although some will live for up to 3 years (Moyle 2002). Longfin smelt were recently proposed for listing under CESA and the federal ESA (Bay Institute et al 2007).…”

Section: Life History Traits Of the Fishes Examinedmentioning

confidence: 99%

“…In recent years, these conflicts have increased because many pelagic fishes in the estuary have dropped to record low abundances while demands for water have increased ). Historically, many fishes in the estuary responded favorably to wetter years because high inflows usually improved spawning and rearing conditions in the estuary (Stevens and Miller 1983;Sommer et al 1997;Kimmerer et al 2001;Bennett 2005;Feyrer et al 2007;Rosenfield and Baxter 2007). The strength of these relationships has diminished during the last few years for several possible reasons, including habitat changes, water diversions, food web alterations, and stock-recruitment effects .…”

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confidence: 99%

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Factors Affecting Fish Entrainment into Massive Water Diversions in a Tidal Freshwater Estuary: Can Fish Losses be Managed?

Grimaldo

Sommer²,

Ark³

et al. 2009

N American J Fish Manag

114

140

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Abstract.-We examined factors affecting fish entrainment at California's State Water Project and Central Valley Project, two of the largest water diversions in the world. Combined, these diversions from the upper San Francisco Estuary support a large component of the municipal and agricultural infrastructure for California. However, precipitous declines in the abundance of several estuarine fish species, notably the threatened delta smelt Hypomesus transpacificus, have generated major concern about entrainment as a possible cause of the declines. We examined a 13-year data set of export pumping operations and environmental characteristics to determine factors affecting entrainment (as indexed by salvage at fish screens) and the potential for manipulation of these factors to improve conditions for fish. Entrainment of three migratory pelagic species-delta smelt, longfin smelt Spirinchus thaleichthys, and striped bass Morone saxatilis-was primarily determined by the seasonal occurrence of particular life stages close to the export facilities. We also found that the direction and magnitude of flows through the estuary and to the export facilities were reasonable predictors of pelagic fish entrainment. Entrainment of resident demersal species (prickly sculpin Cottus asper and white catfish Ameiurus catus) and littoral species (Mississippi silverside Menidia audens and largemouth bass Micropterus salmoides) was not explained by diversion flows, although large numbers of individuals from these species were collected. Our study suggests that entrainment of pelagic species can be effectively reduced by manipulating system hydrodynamics.

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“…A regional demographic unit of longfin smelt (Spirinchus thaleichthys), a species found along the Pacific Coast from Alaska to southern California, was found to warrant listing by FWS from open water surveys in the San Francisco estuary (FWS 2012). Longfin smelt numbers derived from those surveys, which are assumed to provide a surrogate measure of the status and trends in overall numbers of the fish in the estuary, are correlated with outflow through the Delta during spring months (Rosenfield and Baxter 2007). However, water export policy is being determined based on this correlation, even though the surveys cover only a fraction of the area of the San Francisco estuary utilized by the fish.…”

Section: History Of Surrogates In Conservation Biologymentioning

confidence: 99%

The use of surrogates in implementation of the federal Endangered Species Act—proposed fixes to a proposed rule

Murphy

Weiland²

2014

J Environ Stud Sci

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The US Fish and Wildlife Service and National Marine Fisheries Service recently proposed to amend existing regulations that implement the Endangered Species Act's interagency consultation process by codifying their preexisting practice of using surrogates to express the amount or extent of incidental take of listed species. The agencies contend that amendments both are necessary as a practical matter and are defensible on ecological grounds. They propose the use of surrogates, either in the form of a substitute species filling in for a species that is challenging to observe or measure, or a land-cover type or another habitat attribute, as proxies for the amount or extent of anticipated take. We contend that the proposed rule leaves the process of surrogate selection and application without essential implementation details and describe five essential steps in surrogate selection and validation. In sum, an obligatory validation procedure should clearly articulate the reasoning behind the selection of the surrogate, including describing the similarities in responses by the surrogate and target species to the same environmental phenomena, linking demographic responses to habitat extent and condition, and describing the uncertainties that accompany the relationship between the status and trends of the surrogate and those of the target species or its habitat under common circumstances.

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Population Dynamics and Distribution Patterns of Longfin Smelt in the San Francisco Estuary

Cited by 48 publications

References 26 publications

Effects of high temperatures on threatened estuarine fishes during periods of extreme drought

Effects of high temperatures on threatened estuarine fishes during periods of extreme drought

Factors Affecting Fish Entrainment into Massive Water Diversions in a Tidal Freshwater Estuary: Can Fish Losses be Managed?

The use of surrogates in implementation of the federal Endangered Species Act—proposed fixes to a proposed rule

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