Background
The San Joaquin River is the second-longest river in California measuring 330 miles. It originates high on the western slopes of the Sierra Nevada and drains most of the area from the southern border of Yosemite, south to Kings Canyon National Park. The San Joaquin River's tributaries include the Stanislaus River, Tuolumne River, Merced River, Calaveras River and Mokelumne River.
The San Joaquin River once supported the southernmost Chinook salmon run in North America. As a result of seasonal water diversions and the operation of upstream hydropower reservoirs, by 1928, the California Department of Fish and Game had issued a bulletin reporting that there were "very few" salmon remaining in the San Joaquin River above the Merced River and the "historical" salmon fishery that once existed had been "severely depleted." Although some sources claim that the river may have once supported large runs of both fall-run and spring-run Chinook salmon up to 300,000 returning adults annually, these claims appear to be greatly exaggerated, given the river's hydrology, San Joaquin Valley temperatures, and the impacts of these factors on available salmon habitat. An official with the California Department of Fish and Game stated in 1930s that the spawning gravels in the river were only sufficient to support, at most, about 15,000 returning fish. During that same time (late 1930s - early 1940s), the salmon counts taken by the California Department of Fish and Game at the Mendota Dam fish ladder showed about 3,000-7,000 salmon returning each year to spawn. While some sources claim that steelhead trout may have also been present in the river in the 19th century, there is no known evidence to confirm this speculation.
Fisheries Monitoring
Mossdale Trawl
The California Department of Fish & Game (CDFG) has operated the Kodiak Trawl in the lower San Joaquin River annually since 1988. The purpose of this annual survey is to estimate the juvenile Chinook (smolt) outmigration from the San Joaquin River; evaluate temporal and spatial distributions; and examine the relationship between juvenile Chinook salmon and environmental variables. Sampling by CDFG normally occurs during a 10 week period beginning in April and extending through mid-June from Mossdale to the Head of Old River. The U.S. Fish & Wildlife Service (USFWS) operates the trawl during the remainder of the years on an intermittent basis (i.e., approximately 3 days per week).
Juvenile Beach Seining
U.S. Fish & Wildlife Seining
Weekly beach seining surveys are conducted to estimate the relative inter and intra-annual abundance and distribution of all races of salmonid fry using the delta as a rearing and nursery area. All native and non-native fishes are identified, measured, and enumerated.
Starting in the mid-1970's, beach seining has been conducted at numerous locations (Sampling Map) in the Lower Sacramento and San Joaquin Rivers, the Delta, and the San Francisco, Suisun, and San Pablo Bay areas. For specific details on the beach seining program please see Beach Seining Reports. Each site is seined between two and four times monthly.
TID/MID Seining
Seining surveys have been conducted during the juvenile Chinook outmigration period in the Tuolumne and San Joaquin rivers since 1986 by the Turlock & Modesto Irrigation Districts. The purpose of the surveys is to document juvenile salmonid size, distribution, and relative abundance in nearshore rearing habitats, as well as gather similar information on other fish species.
Restoration
Since Friant Dam became fully operational in the late 1940s, approximately 60 miles of the river have been dried up in most years, eliminating salmon above the river's confluence with the Merced River. A historic agreement to restore water flows for salmon in the San Joaquin River below Friant Dam near Fresno while undertaking one of the West's largest river restorations was announced in 2006. The Settlement Agreement is based on two goals and objectives:
- A restored river with continuous flows to the Sacramento-San Joaquin River Delta and naturally reproducing populations of Chinook salmon.
- A water management program to minimize water supply impacts to San Joaquin River water users.
Accomplishing these goals will require funding and constructing extensive channel and structural improvements in many areas of the river, including some that have been without flows (except for occasional flood releases) for decades.