Diet and relative abundance of Rock Bass, a recent invader in the lower Lake Washington system, Washington State

Authors

• Roger A. Tabor, U.S. Fish and Wildlife Service, Western Washington Fish and Wildlife Conservation Office, 500 Desmond Drive SE, Lacey, WA 98503Follow
• Aaron D. Bosworth, Washington Department of Fish and Wildlife, 16018 Mill Creek Blvd., Mill Creek, WA 98012
• Joseph Short, Washington Department of Fish and Wildlife, 16018 Mill Creek Blvd., Mill Creek, WA 98012
• Daniel Garrett, Washington Department of Fish and Wildlife, 16018 Mill Creek Blvd., Mill Creek, WA 98012; Present address: Washington Department of Fish and Wildlife, 2315 North Discovery Place, Spokane Valley, WA 99216
• George Chapman, Washington Department of Fish and Wildlife, 16018 Mill Creek Blvd., Mill Creek, WA 98012
• Katherine Gordon, Washington Department of Fish and Wildlife, 16018 Mill Creek Blvd., Mill Creek, WA 98012
• Alanna Sutton, Washington Department of Fish and Wildlife, 16018 Mill Creek Blvd., Mill Creek, WA 98012
• Jordan N. Kinberg, U.S. Fish and Wildlife Service, Western Washington Fish and Wildlife Conservation Office, 500 Desmond Drive SE, Lacey, WA 98503; Present address: Lone Pine High School, 538 South Main Street, Lone Pine, CA 93545
• Marc Solano, U.S. Fish and Wildlife Service, Western Washington Fish and Wildlife Conservation Office, 500 Desmond Drive SE, Lacey, WA 98503; Present address: Sea Grant Alaska, Kodiak, AK 99901
• Lauren Mason-Sarantopulos, U.S. Fish and Wildlife Service, Western Washington Fish and Wildlife Conservation Office, 500 Desmond Drive SE, Lacey, WA 98503

Abstract

Rock Bass (Ambloplites rupestris) is a recent invader in the lower Lake Washington ecosystem whose potential impacts to this system are not known. We assessed changes in the relative abundance of Rock Bass and other centrarchid basses and documented the diet of Rock Bass during months of juvenile salmonid migrations (February–July). Rock Bass were collected primarily with gill nets in littoral zones of Lake Washington (2022–2024) and the Lake Washington Ship Canal (2018–2019, 2021–2023; LWSC). We sampled 3 areas in Lake Washington and 1 area of the LWSC, and in all 4 areas, Rock Bass were relatively more abundant than Largemouth Bass (Micropterus salmoides) or Smallmouth Bass (M. dolomieu). At the south end of Lake Washington (near Cedar River outlet), Rock Bass preyed heavily on migrating Sockeye Salmon (Oncorhynchus nerka) fry from February to April. Juvenile salmonids were rarely consumed in the other areas of Lake Washington and the LWSC and made up a minor component of the diet. Other major prey items of Rock Bass in Lake Washington consisted of signal crayfish (Pacifastacus leniusculus), adult Threespine Stickleback (Gasterosteus aculeatus), juvenile Yellow Perch (Perca flavescens), sculpin (Cottus spp.), opossum shrimp (Neomysis mercedis), and aquatic insects; however, the importance of these prey items varied widely among areas, years, and size classes. In 2018 and 2019 during low Threespine Stickleback abundance, Rock Bass in the LWSC consumed mostly crayfish and small invertebrates. During years in which Threespine Stickleback populations were high (2021–2023), Rock Bass in the LWSC consumed primarily adult Threespine Stickleback, crayfish, and opossum shrimp. As Rock Bass grew, they became progressively more piscivorous; however, some level of piscivory was observed in all size groups. Because Rock Bass are now abundant and have a broad diet, they have the potential to impact the Lake Washington and LWSC food webs through a variety of pathways.


La lobina de roca (Ambloplites rupestris) es un pez invasor reciente en el ecosistema del bajo lago Washington, y aún se desconoce su posible impacto sobre este sistema. Evaluamos los cambios en la abundancia relativa de la lobina de roca y otras lobinas centrárquidas, y documentamos su dieta durante los meses de migración de los salmónidos juveniles (febrero–julio). Recolectamos lobinas de roca principalmente con redes de enmalle en zonas litorales del lago Washington del 2022 al 2024 y en el Canal del Lago Washington (Lake Washington Ship Canal, LWSC) durante los años 2018–2019, 2021–2023. Muestreamos tres áreas del lago Washington y un área del LWSC. En las cuatro áreas muestreadas, la lobina de roca fue relativamente más abundante que la lobina negra (Micropterus salmoides) o la lobina de boca chica (M. dolomieu). En el extremo sur del lago Washington (cerca de la desembocadura del río Cedar), la lobina de roca se alimentó principalmente de crías de salmón rojo (Oncorhynchus nerka) migrantes entre febrero y abril. Los salmónidos juveniles rara vez fueron consumidos en las otras áreas del lago Washington y del LWSC, y constituyeron un componente menor de la dieta. Otras presas importantes de la lobina de roca en el lago Washington incluyeron cangrejos señal (Pacifastacus leniusculus), peces espinosos adultos (Gasterosteus aculeatus), juveniles de perca amarilla (Perca flavescens), cóctidos (Cottus spp.), mísidos (Neomysis mercedis) e insectos acuáticos. Sin embargo, la relevancia de estas presas varió ampliamente entre las zonas, el año y la clase de tamaño de los peces. En 2018 y 2019, durante el periodo de baja abundancia del pez espinoso, las lobinas de roca en el LWSC consumieron principalmente cangrejos y pequeños invertebrados. Durante los años en que las poblaciones de peces espinosos fueron altas (2021–2023), las lobinas de roca del LWSC se alimentaron principalmente de adultos de esta especie, seguido de cangrejos y mísidos. A medida que las lobinas de roca crecieron, se volvieron progresivamente más piscívoros. No obstante, se observó cierto nivel de piscivoría en todos las clases de tamaño. Dado que, actualmente la lobina de roca es más abundante y tiene una dieta amplia, tiene el potencial de impactar las redes tróficas del lago Washington y del LWSC a través de diversas vías.

Recommended Citation

Tabor, Roger A.; Bosworth, Aaron D.; Short, Joseph; Garrett, Daniel; Chapman, George; Gordon, Katherine; Sutton, Alanna; Kinberg, Jordan N.; Solano, Marc; and Mason-Sarantopulos, Lauren (2026) "Diet and relative abundance of Rock Bass, a recent invader in the lower Lake Washington system, Washington State," Western North American Naturalist: Vol. 86: No. 1, Article 7.
Available at: https://scholarsarchive.byu.edu/wnan/vol86/iss1/7