Striped Bass Migration Patterns Across Varying Salinity Gradients Inferred with Otolith Chemistry​

Abstract

Striped Bass are an invasive species in California and are a predator of native endangered juvenile Chinook Salmon. Although anadromous, there is evidence of resident population contingents along the Atlantic Coast. If a resident contingent exists in CA, then predation may occur year-round, further lowering juvenile salmonid survival. Therefore, the objective of this study was to determine if resident Striped Bass are present in the California Sacramento-San Joaquin Delta. Striped Bass were collected by CDFW, and NOAA/UCSC researchers from the Delta and San Francisco Bay. After collection, otoliths were removed and aged, and the ratios of Strontium to Calcium (Sr:Ca) and Barium to Calcium (Ba:Ca) were quantified with a Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS). After analysis, the proportion of time each fish spent in the Delta (salinity < 2psu) was inferred using lifetime otolith Sr:Ca transects. If a fish spent ≥ 90% of its life in the Delta, it was considered a resident. The same classification criteria were also used for yearly resident classification. At age 1, 32% of individuals were residents and 20% of fish were lifetime residents in the Delta. Similar to the east coast these results indicate that a resident contingent of Striped Bass exists in the Delta, which likely consumes juvenile salmon whenever they are present in the system.