Delta Smelt Reaches Record Low, Despite High River Flows

Article from Daily Kos.

By Dan Bacher
2017/12/28 · 23:01

In spite of a record water year in Northern California, the abundance of Delta Smelt recorded in the state’s annual fall midwater survey (FMWT) is the lowest in the survey’s 50-year history.

Only two Delta Smelt were collected at Delta index stations in October. One was from Suisun Bay and the other from the confluence of Sacramento and San Joaquin Rivers, reported James White, California Department of Fish and Wildlife environmental scientist, in a memo.

The CDFW collected no Delta Smelt in September, November, or December.

The agency surveyed the Delta smelt, along with other five other pelagic (open water) species, in trawl nets at 100 index stations throughout the Sacramento-San Joaquin River Delta, the largest estuary on the West Coast of the Americas, from September 1 through December 13.

“The population is so low that they can’t find each other to mate,” Tom Cannon, a fish ecologist and consultant for the California Sportfishing Protection Alliance, told the Stockton Record. “We’re lucky to have any smelt.”

During the last big water year, 2011, the number of Delta smelt increased ten times, but not this year.

Maligned by agribusiness groups and San Joaquin Valley Republican Congressman as a “small minnow” supposedly standing in the way of deliveries of Delta water to irrigators, the Delta Smelt is in fact a indicator species that demonstrates the health of the Delta ecosystem like the proverbial “canary in the mine.”

Three other species surveyed by the agency, longfin smelt, striped bass and threadfin shad, did relatively better in the high water flow conditions that hit the Delta from the fall through summer. Two others, threadfin shad and Sacramento splitail, didn’t fare so well.

The health of the fish populations is measured by means of the CDFW’s “abundance index,” a relative measure of abundance.

The abundance index (141) for longfin smelt is the highest since 2013. Seventy Longfin Smelt were collected at index stations.

The index (470) for striped bass is the highest since 2001. Three hundred ninety-nine age-0 Striped Bass were collected at index stations.

The number (3086) for American Shad is the highest since 2003. Two thousand three hundred fifty-seven American Shad were collected at index stations.

The threadfin shad didn’t do as well as its cousin, the American Shad. The threadfin index (291) is the seventh lowest in FMWT history (Figure 4). Only two hundred sixty-two Threadfin Shad were collected at index stations.

The index for the Sacramento splittail “shows a continuing trend of very little to no catch of Splittail in FMWT,” said White.

“One splittail was collected at an index station in December from Suisun Bay. No other Splittail were collected in September, October, or November from index or non-index stations,” said White.

While a number of factors have resulted in the decline of Delta smelt and the other pelagic species, including toxics and invasive species, no factor has helped precipitate the decline of Delta fish species more than the export of massive quantities of water to agribusiness and Southern California water agencies from the state and federal pumping facilities in the South Delta over the past 50 years.

The Delta smelt (Hypomesus transpacificus) is an endangered slender-bodied smelt, about 2.0 to 2.8 in long, in the family Osmeridae. Found only in the upper Sacramento-San Joaquin Estuary of California, it mainly inhabits the freshwater-saltwater mixing zone of the estuary, except during its spawning season, when it migrates upstream to freshwater following winter “first flush” flow events (around March to May), according to Wikipedia. Once the most abundant fish found in the estuary that numbered in the millions, the fish has declined dramatically in recent years.

Because of its one-year lifecycle and relatively low fecundity, the smelt is very susceptible to changes in the environmental conditions of its habitat. Efforts to protect the endangered fish from further decline have focused on limiting or modifying the pumping activities of state and federal water projects in the South Delta. However, these limited efforts have not been enough to prevent the species from becoming functionally extinct in the wild, especially with record exports of water from 2003 to 2007 and then again in 2011.

Bookmark the permalink.

Comments are closed.