Gearty, A.J., T.R. Ignoffo, A.M. Slaughter & W.J. Kimmerer. (2021). Growth and reproductive rates of the dominant copepod Pseudodiaptomus forbesi in response to environmental factors and habitat type in the northern San Francisco Estuary. Aquatic Ecology. 55(3):1-25. MAY 2021.

407223

10.1007/s10452-021-09863-4 [view]

Gearty, A.J., T.R. Ignoffo, A.M. Slaughter & W.J. Kimmerer

2021

55(3):1-25. MAY 2021

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We examined growth and egg production rates of Pseudodiaptomus forbesi (Copepoda: Calanoida) in the northern San Francisco Estuary (SFE), California, USA. Data from several earlier studies were combined with new data to assess the responses of these vital rates to environmental factors. We measured 118 growth rates of early copepodites (C1-C3) and 191 egg production rates (EPRs) during spring-autumn of 10 years between 2006 and 2018. Samples were taken from four habitat types: brackish open water, fresh open water, wetland, and tidal channel. Growth rates averaged 0.21 d(-1) (range 0-0.53 d(-1)), while EPR averaged 2.4 eggs female(-1) d(-1) (range 0-11 eggs female(-1) d(-1)). Mass-specific EPR of females averaged about 20% of copepodite growth rate, meaning that specific egg production rate is not a suitable proxy for specific growth rate of this species. A rectangular hyperbola predicted 24% of the variation in growth rate from chlorophyll concentration and 19% of the variation in EPR (28% with habitat type as a covariate). Most of the chlorophyll values were below levels where growth rate or EPR approach their maxima. Lipid composition in a subset of samples gave no better prediction of growth rate than chlorophyll and was unrelated to EPR. Growth and reproduction of P. forbesi were food-limited most of the time, particularly in the open-water habitats. Despite high variability, these measurements make clear that the chronically low primary production in the northern SFE imposes limits on the food web supporting declining fish populations.

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