Mapping Sturgeon Spawning Habitat in the Lower San Joaquin River
The spawning of adult white sturgeon (Acipenser transmontanus) in the lower San Joaquin River was documented recently by the United States Fish and Wildlife Service (USFWS) (Gruber and others, 2012; Jackson and Eenennaam, 2013). Streamflow on the San Joaquin River has been modified by State and Federal water project operations, and there are a variety of questions regarding the effects on fish habitat. A lack of information on the physical characteristics of the river related to fish habitat (e.g. depth, flow velocity, and substrate) led the USFWS to contact USGS and request undertaking of a habitat mapping study.
This study is part of an overall effort by Department of the Interior to increase the natural productivity of anadromous fish populations in the Central Valley rivers and streams. The primary objective of this study was to map habitat-related physical characteristics along the lower San Joaquin River, with an emphasis on areas known or believed to be associated with white and green sturgeon spawning. These physical attributes of the river could then be used by fisheries biologists to characterize the amount of habitat available for particular species (note: this is not part of this study; this study is focused on collecting the data needed for these characterizations). Other objectives are to document the variations in these physical characteristics between wet and dry years, and to interpret these data and identify potential mechanisms which may cause these variations.
Preliminary results indicate that the dominant bed-material type in the lower San Joaquin River is sand. There are, however, a few localized areas downstream of the confluence of Del Puerto Creek and Orestimba Creek where gravel-sized bed material was found. Research by others has found that coarse bed-material (gravel and cobble) is necessary for the successful incubation of sturgeon eggs (e.g. Parsley and Kofoot, 2013). The bathymetric data spanning multiple years at several sites have also shown a large amount of deposition occurring in the river in the form of sand. The accumulation of the sediment is due to the low transport capacity of the river during dry water years (2012-2014) relative to the sediment supply. Bed-material sampling has only been conducted during dry years; therefore the effect of the hydrologic regime on the bed-material composition during wet years is not known. In sand-bedded rivers, coarse sediment particles can migrant downstream until they reach low-elevation areas (e.g. Hassan and others, 1999). Thus, in the San Joaquin River, gravel may become buried during dry years and subsequently exposed as the finer, sand-sized sediment is flushed out during high-flow events. If that is the case, the exposed gravel would provide greater suitable spawning habitat for sturgeon during wet years than during dry years.
The spawning of adult white sturgeon (Acipenser transmontanus) in the lower San Joaquin River was documented recently by the United States Fish and Wildlife Service (USFWS) (Gruber and others, 2012; Jackson and Eenennaam, 2013). Streamflow on the San Joaquin River has been modified by State and Federal water project operations, and there are a variety of questions regarding the effects on fish habitat. A lack of information on the physical characteristics of the river related to fish habitat (e.g. depth, flow velocity, and substrate) led the USFWS to contact USGS and request undertaking of a habitat mapping study.
This study is part of an overall effort by Department of the Interior to increase the natural productivity of anadromous fish populations in the Central Valley rivers and streams. The primary objective of this study was to map habitat-related physical characteristics along the lower San Joaquin River, with an emphasis on areas known or believed to be associated with white and green sturgeon spawning. These physical attributes of the river could then be used by fisheries biologists to characterize the amount of habitat available for particular species (note: this is not part of this study; this study is focused on collecting the data needed for these characterizations). Other objectives are to document the variations in these physical characteristics between wet and dry years, and to interpret these data and identify potential mechanisms which may cause these variations.
Preliminary results indicate that the dominant bed-material type in the lower San Joaquin River is sand. There are, however, a few localized areas downstream of the confluence of Del Puerto Creek and Orestimba Creek where gravel-sized bed material was found. Research by others has found that coarse bed-material (gravel and cobble) is necessary for the successful incubation of sturgeon eggs (e.g. Parsley and Kofoot, 2013). The bathymetric data spanning multiple years at several sites have also shown a large amount of deposition occurring in the river in the form of sand. The accumulation of the sediment is due to the low transport capacity of the river during dry water years (2012-2014) relative to the sediment supply. Bed-material sampling has only been conducted during dry years; therefore the effect of the hydrologic regime on the bed-material composition during wet years is not known. In sand-bedded rivers, coarse sediment particles can migrant downstream until they reach low-elevation areas (e.g. Hassan and others, 1999). Thus, in the San Joaquin River, gravel may become buried during dry years and subsequently exposed as the finer, sand-sized sediment is flushed out during high-flow events. If that is the case, the exposed gravel would provide greater suitable spawning habitat for sturgeon during wet years than during dry years.