Seasonal Movement Patterns of Striped Bass (Morone saxatilis) in Their Nonnative Range

Abstract

Movement dynamics of nonnative species can change in new environments and differ from native populations. It has been more than 100 years since striped bass (Morone saxatilis) were introduced to the Sacramento-San Joaquin River system in California from the US east coast. Acoustic telemetry from 2011 to 2015 was used to examine striped bass seasonal residence patterns in their nonnative range across three regions—bay, delta and rivers, and the effect of fish length and release river (Sacramento River [SR] vs. Feather River [FR]) on movement. In spring, SR striped bass (n = 52) increased travel speed by 39% and river residence by 63% relative to other seasons, which is consistent with spawning migrations. In summer, SR striped bass spent the most time in the bay (mean = 28.2 ± 30.9 days) relative to other seasons and across regions. In winter, 87% of striped bass were detected in the delta over 42% in the bay and 25% in the river. Release river also affected movement behaviors—FR striped bass (n = 11) spent more time in the river in all seasons compared to SR bass. Striped bass with sufficient tag life (n = 17) traveled farther distances in 365 days (mean = 1248 ± 405 km, range: 641–2212 km) with increasing fish length. Seasonal patterns observed appeared to follow seasonal prey sources throughout the San Francisco Estuary. Individual behaviors, however, were highly variable, and this flexibility may be an important trait that has allowed striped bass to persist in their nonnative range.