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Mississippi Silversides

Mississippi Silversides Native to the Mississippi River drainage and coastal streams on the eastern side of the United States, Mississippi silversides have been abundant in the Delta and San Francisco Estuary since at least 1975, after their introduction to California in Blue Lakes and Clear Lake in 1967. While they are not typically thought of as a fish predator, they may be important predators of larval Delta smelt because they will readily consume Delta smelt in the laboratory and, by virtue of their high densities in delta smelt spawning areas, they are highly likely to come in contact with larval smelt.

In collaboration with researchers at the Genomic Variation Laboratory at the University of California, Davis and Cramer Fish Sciences (funded by a grant from the State and Federal Contractors Water Agency), we are using PCR-based genetic techniques to detect predation of Delta smelt by Mississippi silversides. . These new techniques allow for a dramatic increase in effectiveness compared to previous larval fish predation studies.  For example, laboratory studies have found that only 3% of fish larvae can be visually identifiable 60 minutes post-ingestion, whereas we have been able to detect delta smelt DNA in the stomachs of silversides up to 36 hours post-ingestion.

In the spring of 2010, we conducted a pilot study to test the field methods for implementing our new technique.  Over the course of three weeks, we sampled over 600 silversides via Kodiak trawls and beach seining in the Sacramento Deepwater Ship Channel.  Based on the results of the pilot study, a full larval smelt predation study was designed for implementation during the spring of 2011.  Our current sampling spans most of the north delta including Liberty Island, the Sacramento Deepwater Ship Channel, and Cache and Lindsey Sloughs.  Fish are collected using an electro-fishing vessel (supplied by the California Department of Fish and Game), plus beach seining and Kodiak trawls.  In addition to silversides, we are also analyzing stomach samples from juvenile striped bass and largemouth bass so as to get a more complete picture of larval smelt predation patterns.

Recent Results