fish report header

Surviving the South Delta

One of the most intensive fishery studies ever conducted in California's Sacramento-San Joaquin Delta culminated in 2011. The twelve-year study, known as the Vernalis Adaptive Management Program (VAMP), was a multi-organization effort designed to evaluate and improve the survival of salmon smolts migrating through the San Joaquin River Basin. The study investigated how salmon survival may be affected by changes in environmental variables such as river flow and water exports. A technical report summarizing the 2011 results is now available online.


FISHBIO collaborated with a number of other groups to tag, release, and track fish for VAMP (see Follow that fish). In 2011, a total of 1,895 Chinook salmon smolts and 2,195 steelhead smolts were surgically implanted with acoustic tags and released into the San Joaquin River at Durham Ferry. Fish can take multiple pathways through the Delta to the ocean, and the choice of route can affect their survival. Acoustic receivers were deployed throughout the Delta to calculate route-specific survival, and mobile tracking was conducted to determine where mortality was greatest. The two investigated routes were Old River, which heads toward water export facilities and fish salvage facilities, and the main stem San Joaquin River, which historically has had greater survival (Brandes and McLain 2001). Of the two routes that Chinook salmon selected in 2011, Old River had greater survival (4%) than the San Joaquin River (1%). The overall 2011 survival of 2% is consistent with other studies that show smolt survival has been declining in the Delta. Coded-wire tag studies between 1994 and 2001 indicated that survival through the Delta ranged between 15% and 50%. However, CWT and acoustic studies since 2003 have shown survival to be lower than 12% in the south Delta.


The development of acoustic telemetry technology has completely transformed our ability to study fish movement and survival. Biologists can now track the migration of individual fish throughout the Delta and even determine approximate locations where fish are likely eaten by predators. This has identified key mortality areas in the Delta and may help us understand why survival has declined so drastically over the last decade. The use of mobile tracking during the VAMP study helped identify locations where tags accumulated, presumably from predation. Three locations were identified as predation "hot spots": 78 tagged smolts were lost at the the Stockton Deep Water Ship Channel on the San Joaquin River, 48 at the Grant Line Canal, and 37 in front of the trash racks at the Tracy Fish Facility in Old River. Previous years' data suggests that the scour hole near the head of Old River and a railroad bridge in Stockton are also areas of high fish mortality on the San Joaquin River (Vogel 2010). Continued smolt outmigration monitoring studies and an increased effort to monitor non-native predator populations may help us solve some of the fish survival issues that have plagued the Delta for so many years.

Follow Us! Like us on Facebook Follow us on Twitter View our photos on flickr View our videos on YouTube
email list
Recent Blog Post

Little fishers 

You're never too young to  start fishing in the Mekong River basin. In places like Lao PDR where people depend on fish and other aquatic animals for subsistence, all the members of a family often need to pitch in to harvest food, regardless of age or gender. During the weekends, rural children usually spend time helping their parents find more food. Scoop nets are a common type of fishing gear that girls and women use, similar to lift nets (See Need a lift?). While visiting Tha Thout village in Khammouane province in central Lao PDR, FISHBIO staff took these photos of children using scoop nets to harvest aquatic insects and larvae. Some girls in this village also collect water bugs with their hands, as shown in this video. When they return home, they will likely use the insects to make food for their parents, either mixing in soup with vegetables or frying them to eat with sticky rice and chili sauce.


Scoops nets are a traditional type of gear developed to fish without harming all aquatic life. People in Tha Thout village believe that the diversity of the aquatic ecosystem... Read more> 

IN THE NEWS: Recent stories you might have missed...
Lahontan cutthroat trout make a comeback
The New York Times  

For most fishermen a 20-pound trout is a trophy, but for Paiute tribe members and fish biologists here the one Matt Ceccarelli caught was a victory.
That Lahontan cutthroat trout he caught last year, a remnant of a strain that is possibly the largest native trout in North America, is the first confirmed catch of a fish that was once believed to have gone extinct. The fish has been the focus of an intense and improbable federal and tribal effort to restore it... Read more>  

Governor urges fast review of Delta tunnels

Sacramento Bee     

Gov. Jerry Brown wants federal officials to expedite review of the controversial Bay Delta Conservation Plan, his proposal to build two giant water diversion tunnels in the Sacramento-San Joaquin Delta. In a letter to the U.S. secretaries of Interior and Commerce, Brown called on the agencies to release an environmental impact statement and Federal Register notice on the project this summer. The intent is to ensure this process coincides with his own administration's plan to release a state-level environmental impact report... Read more>  

Small dam on Stanislaus floated
Planet Earth Online

The age of massive hydroelectric dam construction ended several decades ago in the United States, but it could be that an era of building small hydro projects is just beginning. The U.S. House of Representatives last week approved a bill that would eliminate environmental hurdles for at least some small hydro projects - those on canals or pipelines operated by the U.S. Bureau of Reclamation. And though the bureau hasn't identified any prospective projects on the facilities it operates in the immediate region... Read more 

Lucrative fish-smuggling trend active in region
Imperial Valley Press 

When Calexico resident Song Shen Zhen, 73, recently drove through a Calexico Port of Entry, a U.S. Customs and Border Protection officer noticed plastic grocery bags under backseat floor mats. There weren't drugs inside the bags but something just as illegal and lucrative: 27 dried swim bladders of the endangered Totoaba macdonaldi fish found only in Baja California's Gulf of California. The species is federally protected in both the U.S. and Mexico... Read more > 

Genetic study finds Ice Age salmon refuge
BBC News

An area of coastal waters around North-West France has been identified as a site for a previously unknown ice-free refuge for salmon during the Ice Age.

 Researchers said the isolated marine haven would help explain the "genetic mosaic" of British and Irish salmon. They added that fish from this refuge bred with fish from the Iberian peninsula as they migrated into UK waters as the ice receded. The findings have been published in the journal Heredity. "There has been a lot of work done on terrestrial organisms and their refugia at the time of the last glacial maximum," explained co-author Jamie Stevens... Read more >