San Francisco Estuary mysid abundance in the fall, and the potential for competitive advantage of Hyperacanthomysis longirostris over Neomysis mercedis

Avila, Michelle; Hartman, Rosemary

doi:10.51492/cfwj.106.3

Cited by 3 publications

(3 citation statements)

References 17 publications

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“…It was first documented in the estuary in 1993, where it was most likely introduced via ballast water (Modlin and Orsi 1997). After its introduction, H. longirostris quickly became the most abundant mysid in the estuary, replacing the native mysid, Neomysis mercedis, as the dominant catch in the CDFW EMP Zooplankton Survey and Fall Midwater Trawl mysid trawls (Avila and Hartman 2020;Barros 2021;. Hyperacanthomysis longirostris is found throughout the upper estuary, at higher temperatures and salinities than N. mercedis, and is smaller at maturity than the native N. mercedis.…”

Section: Target Taxamentioning

confidence: 99%

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Years of Drought and Salt: Decreasing Flows Determine the Distribution of Zooplankton Resources in the San Francisco Estuary

Barros,

Hartman,

Bashevkin

et al. 2024

SFEWS

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The San Francisco Estuary (estuary) and the Sacramento–San Joaquin Delta (the Delta) in California face significant challenges in managing water resources during extended droughts. Zooplankton are a vital trophic link between phytoplankton producers and higher-level consumers such as predatory zooplankton and fish. However, there is still much to be learned about what drives zooplankton abundance and how they respond to drastic changes in environmental conditions, such as droughts. We found that during drought years zooplankton abundance and distribution changes varied for examined taxa. Significant declines in the abundance of Daphnia spp. and the copepod Pseudodiaptomus forbesi occurred in the Suisun Marsh and Suisun Bay regions. In contrast, abundance of the non-native copepod Limnoithona tetraspina increased in Suisun Marsh and the South-Central Delta during those same drought conditions. Salinity is a strong determinant of the presence and abundance of the studied taxa, and we showed that changes in the distribution of salinity low outflow conditions were an important factor in the regional abundance of zooplankton. Because of the expected increase in the frequency and severity of regional droughts, understanding how these conditions affect zooplankton in the estuary will benefit scientists and resource managers who aim to improve conditions for native fishes.

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Section: Target Taxamentioning

confidence: 99%

“…Hyperacanthomysis longirostris is found throughout the upper estuary, at higher temperatures and salinities than N. mercedis, and is smaller at maturity than the native N. mercedis. (Avila and Hartman 2020).…”

Section: Target Taxamentioning

confidence: 99%

Years of Drought and Salt: Decreasing Flows Determine the Distribution of Zooplankton Resources in the San Francisco Estuary

Barros,

Hartman,

Bashevkin

et al. 2024

SFEWS

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“…The metabolic theory of ecology predicts shrinking ectotherm body size with increasing temperatures because body size and temperature affect the metabolic rate of ectotherms (Brown et al 2004). Evidence for shrinking body sizes in the upper estuary with warming temperatures has been limited to invertebrate communities (Bouley and Kimmerer 2006;Avila and Hartman 2020) and a few fish species (Chinook Salmon smolts, Oncorhynchus tshawytscha; Munsch et al 2019;Yanagitsuru et al 2021), and warming temperatures are expected to further reduce the growth window of fishes like Delta Smelt (Brown et al 2016). However, a declining food base for pelagic fishes, in part from the invasion of non-native taxa (e.g., Potamocorbula amurensis, Corbicula fluminea; Feyrer et al 2003;Greene et al 2011;Lucas and Thompson 2012), may exacerbate the shrinking effects of a warmer climate in the upper estuary as found for other ectothermic communities (Crozier et al 2010;Cross et al 2015;O'Gorman et al 2016;Nelson et al 2017).…”

Section: Climate Change Effects On Delta Smelt In the Upper Estuarymentioning

confidence: 99%

Climate Change Scenarios for Air and Water Temperatures in the Upper San Francisco Estuary: Implications for Thermal Regimes and Delta Smelt

Huntsman,

Brown (posthumous),

Wulff

et al. 2024

SFEWS

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Climate projections and their effects have been evaluated in the San Francisco Estuary as part of the U.S. Geological Survey’s CASCaDE2 project. Understanding the ecological effects of climate change can help manage and maintain the ecological health and productivity of the San Francisco Estuary. In this study, we assessed downscaled air temperature data from 10 global climate models (GCMs) under two representative concentration pathway (RCP) trajectories for greenhouse gas concentrations for three regions of the San Francisco Estuary: Suisun and Grizzly Bays, Suisun marsh, and the Sacramento-San Joaquin Delta. We also used previously derived regression models to estimate future water temperatures at 16 locations in the upper San Francisco Estuary. We used a thermal regime approach to summarize water temperature projections to investigate changes to the thermal regime of the upper San Francisco Estuary and used the Delta Smelt (Hypomesus transpacificus) to demonstrate the impacts that a warming climate may have on the habitat needs of this fish species. Our results suggested there were no major differences in the extent of air temperature warming among the three regions. Annual average air temperatures were projected to increase approximately 2.0 and 4.7°C by the end of the century for the low and high RCP scenarios, respectively. We found timing, frequency, and magnitude metrics varied by period and RCP scenario, while duration and variability metrics varied by space for water temperature thermal regimes. For example, the spawning window for Delta Smelt (thermal regime duration metric) is projected to expand in the future, with spawning starting earlier for both RCP scenarios for most sites. Although our thermal regime analysis focused on the life history of Delta Smelt, similar approaches could be used to assess climate change threats to a wide array of native and invasive terrestrial and aquatic species found in San Francisco Estuary.

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Larval and juvenile Longfin Smelt diets as a function of fish size and prey density in the San Francisco Estuary

Burris

Baxter

Burdi

2022

California Fish and Wildlife Journal

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The density and quality of zooplankton prey affect the feeding success of larval and juvenile fishes and thus can drive growth, survival, and recruitment. As part of a larger effort investigating potential causes of a pelagic fish decline, we examined regional feeding success (food presence/absence, stomach fullness), diet composition and prey selection of young Longfin Smelt (Spirinchus thaleichthys) in spring and summer as a function of fish size and prey availability in the San Francisco Estuary. We conducted our sampling during two wet and two dry years, because weather and river flow influence prey community composition and location. Larval and juvenile fish showed evidence of food limitation: high proportions of empty stomachs (≤ 70%) and stomach contents totaling <10% of maximum stomach content volume. The total weight of prey consumed increased with fish length, and in most regions and years this resulted from fish consuming larger prey as they grew; however, in many regions during dry years, fish consumed greater numbers of prey instead of larger prey as they grew. Larval fish preferentially consumed Eurytemora spp. except when rotifers or barnacle nauplii occurred in extremely high densities. Juvenile fish consumed a greater diversity of prey yet relied on mysids in most regions and years. Adult calanoid copepods (Pseudodiaptomus spp., Eurytemora spp., and Acartia spp.) were regionally important in juvenile diets and were positively selected when mysids were in low densities, mostly in eastern regions during dry years. This switch from much larger mysids to smaller calanoid copepods explains the increase in prey number (instead of prey size) consumed in these regions. These results, coupled with food limitation in most regions, suggest that the current densities and quality of zooplankton in the San Francisco Estuary are limiting feeding success and potentially growth and survival of young Longfin Smelt.

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San Francisco Estuary mysid abundance in the fall, and the potential for competitive advantage of Hyperacanthomysis longirostris over Neomysis mercedis

Cited by 3 publications

References 17 publications

Years of Drought and Salt: Decreasing Flows Determine the Distribution of Zooplankton Resources in the San Francisco Estuary

Years of Drought and Salt: Decreasing Flows Determine the Distribution of Zooplankton Resources in the San Francisco Estuary

Climate Change Scenarios for Air and Water Temperatures in the Upper San Francisco Estuary: Implications for Thermal Regimes and Delta Smelt

Larval and juvenile Longfin Smelt diets as a function of fish size and prey density in the San Francisco Estuary

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