Assessments at multiple levels of biological organization allow for an integrative determination of physiological tolerances to turbidity in an endangered fish species

Hasenbein, Matthias; Fangue, Nann A.; Geist, Juergen; Komoroske, Lisa M.; Truong, Jennifer; McPherson, Rina; Connon, Richard E.

doi:10.1093/conphys/cow004

Cited by 27 publications

(32 citation statements)

References 102 publications

(146 reference statements)

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“…For reference, Vinagre et al [ 38 ] found that a 1°C increase in water temperature increased the gastric evacuation rate of juvenile Solea senegalensis by ~12% between 14 and 20°C. In terms of turbidity, Delta Smelt exhibit an optimal feeding rate between 25 and 80 NTU [ 65 ] and mean turbidity in both freshwater and brackish habitats both fell within this range (31.8 and 40.6 NTU in fresh and brackish water). Similarly, Baskerville-Bridges et al [ 66 ] found that Delta Smelt were ineffective predators in clear water.…”

Section: Discussionmentioning

confidence: 99%

Foraging and metabolic consequences of semi-anadromy for an endangered estuarine fish

et al. 2017

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Diadromy affords fish access to productive ecosystems, increasing growth and ultimately fitness, but it is unclear whether these advantages persist for species migrating within highly altered habitat. Here, we compared the foraging success of wild Delta Smelt—an endangered, zooplanktivorous, annual, semi-anadromous fish that is endemic to the highly altered San Francisco Estuary (SFE)—collected from freshwater (<0.55 psu) and brackish habitat (≥0.55 psu). Stomach fullness, averaged across three generations of wild Delta Smelt sampled from juvenile through adult life stages (n = 1,318), was 1.5-fold higher in brackish than in freshwater habitat. However, salinity and season interacted, with higher fullness (1.7-fold) in freshwater than in brackish habitat in summer, but far higher fullness in brackish than freshwater habitat during fall/winter and winter/spring (1.8 and 2.0-fold, respectively). To examine potential causes of this interaction we compared mesozooplankton abundance, collected concurrently with the Delta Smelt, in freshwater and brackish habitat during summer and fall/winter, and the metabolic rate of sub-adult Delta Smelt acclimated to salinities of 0.4, 2.0, and 12.0 psu in a laboratory experiment. A seasonal peak in mesozooplankton density coincided with the summer peak in Delta Smelt foraging success in freshwater, and a pronounced decline in freshwater mesozooplankton abundance in the fall coincided with declining stomach fullness, which persisted for the remainder of the year (fall, winter and spring). In brackish habitat, greater foraging ‘efficiency’ (prey items in stomachs/mesozooplankton abundance) led to more prey items per fish and generally higher stomach fullness (i.e., a higher proportion of mesozooplankton detected in concurrent trawls were eaten by fish in brackish habitat). Delta Smelt exhibited no difference in metabolic rate across the three salinities, indicating that metabolic responses to salinity are unlikely to have caused the stomach fullness results. Adult migration and freshwater spawning therefore places young fish in a position to exploit higher densities of prey in freshwater in the late spring/summer, and subsequent movement downstream provides older fish more accessible prey in brackish habitat. Thus, despite endemism to a highly-altered estuary, semi-anadromy provided substantial foraging benefits to Delta Smelt, consistent with other temperate migratory fish.

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Section: Discussionmentioning

confidence: 99%

Foraging and metabolic consequences of semi-anadromy for an endangered estuarine fish

et al. 2017

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“…; Hasenbein et al. , ). Lower abundance of Delta Smelt in clear water than in turbid water may occur because they avoid clear water or are eaten by predators in clear water (Feyrer et al.…”

Section: Discussionmentioning

confidence: 98%

“…Turbidity also was not included in the model, although it explained 21% (in summer) or 13% (in autumn) of the deviance in log catch per trawl in two long-term surveys Nobriga et al 2008). Young Delta Smelt that are held in clear water show evidence of physiological stress and will not feed readily, suggesting that low turbidity may limit larval feeding success in the estuary (Baskerville-Bridges et al 2004;Hasenbein et al 2013Hasenbein et al , 2016. Lower abundance of Delta Smelt in clear water than in turbid water may occur because they avoid clear water or are eaten by predators in clear water Nobriga et al 2008).…”

Section: What Is Not In the Model?mentioning

confidence: 99%

Individual‐Based Modeling of Delta Smelt Population Dynamics in the Upper San Francisco Estuary III. Effects of Entrainment Mortality and Changes in Prey

Kimmerer

Rose

2018

Trans Am Fish Soc

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We used an individual‐based model, developed previously for the endangered, endemic Delta Smelt Hypomesus transpacificus, to investigate two factors widely believed to affect its abundance in the San Francisco Estuary: entrainment in large water diversion facilities and declines and species shifts in their zooplankton prey. Previous analyses suggested that these factors had substantial effects on the Delta Smelt population, although evidence is accumulating that other factors, such as contaminants and predation, are also having effects. Simulations were performed for 1995–2005 with either entrainment mortality set to zero or zooplankton biomasses replaced with values sampled from pre‐decline years. The detailed individual‐based and spatial model output was summarized as the annual finite population growth rate (λ). Eliminating entrainment mortality increased the geometric mean λ by 39% through increased survival of larvae and adults. Substituting historical food for present‐day food resulted in variable annual λ values with a geometric mean that was 41% greater than the baseline value (14–81% across 10 alternative food scenarios). Historical food caused higher juvenile consumption and growth rates, leading to larger recruits, earlier maturity, and higher individual fecundity. These results were robust to four sets of simulations using alternative formulations for density dependence, mortality, maturity, and larval growth.

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“…Late larval to juvenile Delta Smelt are more abundant in turbid than in clear water, which has been attributed to reduced predation risk and consequent increase in foraging ability (Feyrer et al 2007;Nobriga et al 2008). Stress responses at high and low turbidity reduced the feeding rate of larval Delta Smelt fed Artemia in the laboratory (Hasenbein et al 2016). The variation in demersal behavior of P. forbesi with turbidity may also contribute to better feeding success of Delta Smelt in turbid than in clear water.…”

Section: Feeding Environment Of Fishmentioning

confidence: 99%

Fine-Scale Distributions of Zooplankton in the Northern San Francisco Estuary

Kimmerer¹,

Slaughter²

2016

SFEWS

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We studied zooplankton distributions in the upper San Francisco Estuary at nested scales of tens to thousands of meters. The purposes of the study were to assess how well the Interagency Ecological Program (IEP) zooplankton monitoring represents abundance, and to investigate the variability of plankton on scales similar to those of foraging by fish. Samples were taken at three sites in the western Sacramento-San Joaquin Delta. We took 18 sets of six samples each with a plankton net along transects from near shore to center channel, and six sets of ten samples in the vicinity of a drifter either in mid-channel or near shore. Sampling took place in June-July 2014 during neap and spring tides, ebb and flood, day and night (transects only). Analysis focused on three common copepod species. Transect samples showed little consistent variation along transects, except that Pseudodiaptomus forbesi was less abundant nearshore than offshore by day at Big Break, the most landward site. The ratio of adults to adults + copepodites was strongly and positively related to turbidity by day but not by night, indicating demersal behavior. Drifter samples showed a minimum standard deviation of log 10 sample counts of about 0.1, indicating that about two-thirds of replicate abundance values were within 80 % to 125% of the mean. A measure of difference between plankton samples at pairs of sample points was unrelated to distance between sample points for drifter samples, weakly related along transects for Limnoithona spp. stages, and strongly related for P. forbesi mainly because of the along-transect gradients at Big Break. The IEP sampling program is representative of plankton abundance except for demersal organisms, which can be tenfold more abundant by night than by day. Small planktivorous fish could forage in patches of up to ~25% higher abundance than the mean.

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Assessments at multiple levels of biological organization allow for an integrative determination of physiological tolerances to turbidity in an endangered fish species

Cited by 27 publications

References 102 publications

Foraging and metabolic consequences of semi-anadromy for an endangered estuarine fish

Foraging and metabolic consequences of semi-anadromy for an endangered estuarine fish

Individual‐Based Modeling of Delta Smelt Population Dynamics in the Upper San Francisco Estuary III. Effects of Entrainment Mortality and Changes in Prey

Fine-Scale Distributions of Zooplankton in the Northern San Francisco Estuary

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