Geology topics

Research about Santa Ana River

Source-linked reports with geographic coverage including Santa Ana River.

5 recordsLinked to original sources

USGS2026

Using a temporary emigration model to estimate abundance of stream fishes from hybrid removal surveys with and without block nets

Monitoring programs are often faced with a decision to allocate resources into either robust spatiotemporal coverage to estimate a population index (e.g., not true abundance) or confirming closed sampling conditions (e.g., with block nets) for an unbiased population estimate at the cost of spatiotemporal coverage. However, making accurate and precise abundance estimates at robust spatiotemporal scales is possible when combining open and closed sampling designs with integrated modeling techniques. We used simulations and a case study of backpack electrofishing surveys in the Santa Ana River, California to test the efficacy of an integrated abundance model (temporary emigration model, TE) to estimate abundance of fishes using removal sampling methods with a hybrid sampling design (sampling with and without block nets during removal sampling). We found that the TE model performed well under most modeling scenarios (sample size, amount of closure violation, number of samples collected during closure), although at least a few samples with block nets were necessary for all parameters to be estimable. When applied to fish surveys in the Santa Ana River, we found that catch of the fishes fit to the TE model (Santa Ana Sucker, Arroyo Chub, Channel Catfish, Largemouth Bass, Yellow Bullhead) showed little evidence that the closure assumption was violated when block nets were not used. Additionally, we found that the abundance of non-native fishes negatively affected the abundance of the native Santa Ana Sucker, which was also found to adversely affect the native fish’s access to critical habitat consisting of gravel and cobble substrate. Our results indicate that the TE model presents a viable solution to common sampling problems that impact many monitoring programs, where precise and accurate population estimates can be made at large spatiotemporal scales even when most samples violate the closure assumption.

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USGS2025

Carbon and nitrogen isotopes of different native fish tissues from the Santa Ana River, California

Objective Stable isotopes are commonly used to understand the role of fishes in aquatic food webs. However, variability in species- and tissue-specific isotopic values can affect the inference that is drawn from a stable isotope study. We evaluated differences in stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among three tissue types (white muscle, caudal fin rays, and eye lenses) for Santa Ana Sucker Pantosteus santaanae and Arroyo Chub Gila orcuttii to inform the design of a stable isotope study in the Santa Ana River, an urban river that is located in southern California. Methods We used multivariate analyses to test for differences in the stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among the three tissue types that were collected from Santa Ana Sucker and Arroyo Chub. We also summarized the variability in isotopic values that was recorded over time in fish eye lenses and interpreted this variability in reference to the spatial patterns in isotopic values that have been previously reported throughout the Santa Ana River. Results We found that fin ray tissue and white muscle tissue were not significantly different for either isotope or fish species. Fish eye lenses were significantly higher in δ 13 C than muscle tissue, and eye lenses were significantly higher in δ 15 N than fin ray tissue for both fishes. We also found a greater range in δ 13 C and δ 15 N across eye lens layers for Santa Ana Sucker (δ 13 C = 2.01 ± 0.96‰, δ 15 N = 4.93 ± 4.18‰) than for Arroyo Chub (δ 13 C = 0.96 ± 0.65‰, δ 15 N = 4.63 ± 1.45‰). Conclusion Our results indicate that fin rays may be a viable nonlethal alternative to white muscle tissue for use in a stable isotope study of native fish of the Santa Ana River. Additionally, eye lenses could provide a chemical history of fishes within the river, but species-specific correction factors may be needed if stable isotope values for eye lenses are to be compared with more conventional tissue types (e.g., white muscle).

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USGS2022

Joint-species analysis reveals potential displacement of native fishes by non-native fishes within the Santa Ana River, California

Accurate estimates of abundance are a cornerstone for resource managers to make effective decisions for fish conservation. However, multiple sampling methods often are required to sample fish communities, and ignoring the detection process can create substantial bias in latent state parameter estimation (e.g., abundance, survival). We developed a joint-species N -mixture model that integrated snorkel, seining, and electrofishing surveys to estimate factors affecting native and non-native fish distributions in the Santa Ana River, California. We found through data integration that native Santa Ana sucker ( Catostomus santaanae ) and arroyo chub ( Gila orcuttii ) were most abundant in wide stream channels, and the abundance of both native fishes were negatively correlated with non-native largemouth bass ( Micropterus salmoides ). Our results highlight the power of integrating multiple data sets into a single analysis and incorporating among-species correlation into abundance modeling. Our results also highlight a pattern of native fish declines that coincides with an expanding largemouth bass population, a concern for the management of native aquatic communities within the Santa Ana River.

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USGS2007

Suspended-sediment rating curve response to urbanization and wildfire, Santa Ana River, California

[1] River suspended-sediment concentrations provide insights to the erosion and transport of materials from a landscape, and changes in concentrations with time may result from landscape processes or human disturbance. Here we show that suspended-sediment concentrations in the Santa Ana River, California, decreased 20-fold with respect to discharge during a 34-year period (1968−2001). These decreases cannot be attributed to changes in sampling technique or timing, nor to event or seasonal hysteresis. Annual peak and total discharge, however, reveal sixfold increases over the 34-year record, which largely explain the decreases in sediment concentration by a nonlinear dilution process. The hydrological changes were related to the widespread urbanization of the watershed, which resulted in increases in storm water discharge without detectable alteration of sediment discharge, thus reducing suspended-sediment concentrations. Periodic upland wildfire significantly increased water discharge, sediment discharge, and suspended-sediment concentrations and thus further altered the rating curve with time. Our results suggest that previous inventories of southern California sediment flux, which assume time-constant rating curves and extend these curves beyond the sampling history, may have substantially overestimated loads during the most recent decades.

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USGS1936

The diurnal fluctuation in the ground‐water and flow of the Santa Ana River and its meaning

In the time alloted for this subject it will be impossible to discuss, in its entirety, all phases of the methods used in computing the loss of water by transpiration from native plant‐life along the Santa Ana River. The results of this work are published in Bulletin 44 of the Division of Water Resources, State of California. The present paper is confined to a discussion of the diurnal fluctuations that occur in the flow of the Santa Ana River and the adjacent ground‐water. On Figure 1 have, been plotted the gage‐height records for a short period (July 5–8, 1935) for eight southern California streams. These records have been selected at random from the large number of records filed in the local office of the United States Geological Survey. Some of these streams have a large drainage‐area, others are small; some are short and steep, others flat and long. The points of measurement range from 15 to 2950 feet above sea‐level. One of the streams (Mojave River) is in the desert‐region; the others drain into the Pacific Ocean. The object of Figure 1 is to demonstrate, that the diurnal fluctuation exists and is, to a large degree, similar at most points of measurement. As a rule, the maximum discharge occurs about 10 o'clock in the morning, and the minimum late in the afternoon. It is readily recognized that these fluctuations are in the main caused by the evaporation and transpiration‐loss in or adjacent to the stream‐channel.

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