Rachel Johnson

Rachel Johnson

Senior Researcher

Rachel is a Research Fisheries Biologist with NOAA Fisheries, Fisheries Ecology Division specializing in applied ecology of freshwater, anadromous and marine fishes. She has 14 + years of experience filling critical data gaps that have been used to better manage water and fisheries resources in California. Rachel has pioneered isotope tools to better understand migration, habitat use, contaminant exposure, and connectivity in fish populations. Her work focuses on understanding mechanisms of population viability and aids in determining critical habitats for reproduction, survival, and growth of endangered species and those targeted by fisheries. She is a translational ecologist dedicated to communicating and synthesizing science to ensure that scientific information is available to resource managers, decision-makers, and the public.

Research Interests & Expertise
  • Fisheries and isotope ecology

Rachel Johnson's Recent Projects

Reconstructing Juvenile Salmon Growth, Condition, and Delta Habitat Use in the 2014-­15 Drought and Beyond

This study uses otolith chemistry and microstructure to monitor how salmon use the Delta as rearing habitat and a migratory corridor, and the mechanisms cuing their outmigration from natal rivers. We will quantify the extent to which Delta-rearing contributes to salmon population resiliency under different conditions (including drought and flood conditions) and provide baseline data to assess population responses to future habitat restoration and changing climate. Physical tags are limited to larger fish that are more sea-ready than fry, and are thus ineffective to estimate the full rearing potential of Delta habitats, while abundance surveys provide only a snapshot of information. Otolith reconstructions allow us to estimate “who” is using the Delta (which populations and life history types), for how long, and their growth rates relative to other rearing habitats. This project will generate empirical data that will inform management actions aimed at maximizing salmon abundance, life history diversity, and resilience to future stressors.