The U.S. Fish and Wildlife Service has completed the first phase of a special drought-related monitoring program for delta smelt on the San Joaquin River at Jersey Point and is making preparations for new surveys which could begin as early as this week with the predicted arrival of rain storms in the area.
As part of the federal response to California’s severe drought, the Service conducted special drought-related surveys for delta smelt for 12 days beginning February 6 at Jersey Point on the San Joaquin River. The monitoring program provided the Service, and state and federal water managers, with valuable near real-time information about the location of delta smelt. The surveys were meant to give water project managers additional time to adapt pumping operations should the imperiled fish moved closer to water diversions in the southern Delta.
With the current lack of rainfall, delta smelt salvage at the Tracy pumps has been non-existent during the 2014 Water Year. No restrictions on water exports have been imposed since the Water Year began in October.
Preliminary results from the Service’s initial surveys showed that close to 60 delta smelt were sampled since February 6, with up to 15 trawls conducted each day. The survey data indicated that delta smelt entrainment risks continue to be low.
If there is substantial rain, however, that risk could increase with increase of Delta flows and turbidity of Delta waterways, as delta smelt could move closer to the water project diversions located near Tracy. With the expected rainfall, the special sampling will resume on a daily basis so that the delta smelt can be tracked during and after the storm.
“Our surveys are accomplishing what they are designed to do, which is to provide near real time information on delta smelt distribution,” said Ren Lohoefener, Director of the Service’s Pacific Southwest Region. “The information we are gathering provides the Service and the water managers the chance to implement strategies that will reduce the risk to delta smelt while providing opportunities to meet water export goals.”
Staff from the Service’s Lodi Fish and Wildlife Office conducted sampling at Jersey Point and will continue in the same location. This added sampling is in addition to the California Department of Fish and Wildlife’s monthly January through May Spring Kodiak Trawl Survey which combined provides an estimated 99 percent probability of detecting delta smelt even if they are at very low density in the lower San Joaquin River. By timing the sampling to focus on the flood tide, the chances of observing delta smelt in the trawls are maximized.
Additional drought-related sampling for delta smelt will continue as considered appropriate throughout the delta smelt spawning season when they’re most mobile, to assess the timing and magnitude of any movement of delta smelt. Sampling will be increased when storms occur that are sufficient to substantially increase water turbidity in the Delta. The information gathered from this sampling will be used to evaluate the likelihood of delta smelt being entrained.
The delta smelt, native to and only found in the San Francisco Bay and Sacramento–San Joaquin Delta Estuary in California, was once a plentiful Delta fish species that has plummeted to record low levels and is listed as a threatened species under the federal Endangered Species Act, and as an endangered species by the State of California.
Logo courtesy U.S. Fish and Wildlife Service