Native Fish Population and Habitat Study - Santa Ana River

Science Center Objects

California Water Science Center scientists further research on two native fish species.

close-up Santa Ana Sucker

Close-up of Santa Ana Sucker (Paul Barrett, USFWS)

Multiple agencies are currently working to establish a Habitat Conservation Plan for the Santa Ana River Watershed. The data currently available for two native fishes in the HCP area, Santa Ana Sucker and Arroyo Chub, are not sufficient to support development of the HCP; therefore, addition data on these two species are needed.

Developing an HCP requires sufficient knowledge of the populations of interest to develop plans for their protection and management. The ability to monitor population abundance and habitat availability with some level of confidence is important when developing such plans. The goals of this study are:

  • Compare snorkeling, seining, and electrofishing as methods for estimating native fish abundance.
  • Develop a population estimate for native fish species in the study area based on the results from Goal 1.
  • Develop a habitat suitability model for the Santa Ana River for Santa Ana Sucker.

In September 2015, selected 50 m lengths of stream in the Santa Ana River between the Rialto wastewater treatment plant and Mission Street will be blocked at both ends using nets and sampled for fish abundance (numbers) by snorkeling, seining, and electrofishing. Data on fish habitat use in the same area will also be collected including depth, water velocity, bottom particle size, and distance to cover at locations where fish are observed. Models of available habitat in the study reaches will be developed based on detailed surveying and computer models.

The fish abundance data will be used to establish a standard methodology for monitoring native fish abundance in the Santa Ana River in support of the HCP. The habitat use data will be compared to the computer models of available habitat to determine the types of habitat features selected by native fishes. Snorkel surveys will be repeated in September 2016 to provide additional data on fish abundance and will presumably represent the second year of monitoring in support of the HCP. A second year of fish habitat use data will also be collected to determine if observed fish habitat utilization is consistent from year to year. Such consistency would support the use of habitat models to predict expected habitat quality in areas that have not been sampled for fish.

This study primarily supports the strategic direction "Understanding Ecosystems and Predicting Ecosystem Change" of the USGS strategic plan. The study also contributes to development of assessment tools that will enable a better understanding of ecosystem properties and processes for use in decision making about the health and welfare of human societies and the environment. The project addresses the Water Resource Area Priority of environmental flows. This project is also supportive of U.S. Geological Survey (USGS) programs and goals in California by increasing the visibility of the Center and individual researchers as experts in the fields of stream ecology.