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The Impact of Submerged Aquatic Vegetation Removal on Fish Predation in a Tidal River Channel.

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Title: The Impact of Submerged Aquatic Vegetation Removal on Fish Predation in a Tidal River Channel.
Authors: Michel, Cyril J.1,2 (AUTHOR) cmichel@ucsc.edu, Burford, Benjamin P.1,2 (AUTHOR), Takata, Lance K.1,2 (AUTHOR), Lehman, Brendan M.1,2 (AUTHOR), Demetras, Nicholas J.1,2 (AUTHOR), Harrison, Lee R.2,3 (AUTHOR)
Source: Estuaries & Coasts. Feb2026, Vol. 49 Issue 1, p1-23. 23p.
Abstract: Proliferation of non-native submerged aquatic vegetation (SAV) can trigger widespread ecosystem changes, and has caused declines in native fish populations around the world. One pathway for these declines is non-native SAV may attract fish predator species by creating habitat structure, altering lower trophic food webs, or affecting predator–prey interactions. It is presumed that non-native vegetation removal will favor native fish, however, fish community responses to SAV removals are not well understood. Using a Before-After-Control-Impact study design in California’s Sacramento-San Joaquin Delta, we found that manual SAV removals decreased abundance of the most common SAV-associated piscivore, largemouth bass (Micropterus salmoides) by 30.2%, yet predation rate on tethered juvenile Chinook salmon (Oncorhynchus tshawytscha; a native fish of management concern) increased by 274.3%. This was likely due to removal of refuge habitat and immigration of an open-water predator, striped bass (Morone saxatilis) into cleared areas, corroborated by video of predation events. We also evaluated predator–prey dynamics using aerobic scope, quantified by the metabolic index (ɸ), or temperature-dependent ratio of environmental oxygen supply and organismal oxygen demand. SAV removals buffered against a 4–6% seasonal decline in ɸ for juvenile salmon (i.e., ɸ declined 78.5–115% less without SAV); whether such gains for prey outweigh the persistent aerobic advantage of predators is unclear. Multispectral imagery indicated that SAV recolonized the removal area within 1 year. While limited in scale, this study puts into question some short-term benefits of small-scale SAV removal efforts for native fish populations, especially where open-water predators are abundant. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
Description
Abstract:Proliferation of non-native submerged aquatic vegetation (SAV) can trigger widespread ecosystem changes, and has caused declines in native fish populations around the world. One pathway for these declines is non-native SAV may attract fish predator species by creating habitat structure, altering lower trophic food webs, or affecting predator–prey interactions. It is presumed that non-native vegetation removal will favor native fish, however, fish community responses to SAV removals are not well understood. Using a Before-After-Control-Impact study design in California’s Sacramento-San Joaquin Delta, we found that manual SAV removals decreased abundance of the most common SAV-associated piscivore, largemouth bass (Micropterus salmoides) by 30.2%, yet predation rate on tethered juvenile Chinook salmon (Oncorhynchus tshawytscha; a native fish of management concern) increased by 274.3%. This was likely due to removal of refuge habitat and immigration of an open-water predator, striped bass (Morone saxatilis) into cleared areas, corroborated by video of predation events. We also evaluated predator–prey dynamics using aerobic scope, quantified by the metabolic index (ɸ), or temperature-dependent ratio of environmental oxygen supply and organismal oxygen demand. SAV removals buffered against a 4–6% seasonal decline in ɸ for juvenile salmon (i.e., ɸ declined 78.5–115% less without SAV); whether such gains for prey outweigh the persistent aerobic advantage of predators is unclear. Multispectral imagery indicated that SAV recolonized the removal area within 1 year. While limited in scale, this study puts into question some short-term benefits of small-scale SAV removal efforts for native fish populations, especially where open-water predators are abundant. [ABSTRACT FROM AUTHOR]
ISSN:15592723
DOI:10.1007/s12237-025-01614-0