OFF THE HOOK: Six Delta fish populations plunge again

The numbers of six Delta fish species documented in the California Department of Fish and Wildlife's fall midwater trawl survey plummeted again in 2012, after a temporary increase among Delta smelt and other species in 2011.

This record-low was predicted by Thomas Cannon, a well-respected fishery biologist who testified on behalf of the California Sportfishing Protection Alliance at State Water Resources Control Board meetings in October and November, 2012.

The most alarming of all of the declines was for threadfin shad, a once abundant forage fish used for striped bass bait on the Sacramento-San Joaquin River Delta.

The threadfin shad reached a record-low abundance level, an index of 41. The index is a relative measure of abundance by the California Department of Wildlife (CDFW).

By contrast, the threadfin shad index reached its highest number recorded, 15,267, in 1997, and was 14,401 in 2001. Last year the number was 228.

The American shad count was the second lowest ever recorded, 415, only exceeded by the record low of 346 in 1976, the first year of a record drought. By contrast, the record abundance was 9,360 in 1972.

The number of Delta smelt, an indicator species found only in the Bay-Delta Estuary that is listed as "endangered" under the Endangered Species Act, was the second lowest on record. The index in 2012 was 42, beginning its backward slide after temporarily increasing to an index of 342 last year.

Longfin smelt, a cousin of the Delta smelt, plummeted to its second lowest recorded abundance, an index of 61. This was only exceeded in 2007, when the number reached a record low of 13.

Striped bass, a popular sport fish that agribusiness has blamed for salmon and Delta smelt declines to divert attention from the impact of Delta water exports on fish species, dropped to the seventh lowest number on record, 125.

The Sacramento splittail, a fish formerly on the Endangered Species List that was delisted by the Bush administration, also had an alarming low number of 1, the second lowest on record. An abundance of 1 was also recorded in 1997, 2002, 2007 and 2009. The record low of "0," when no splittail were reported, was observed in 1977, 2008 and 2010.

Biologist Thomas Cannon predicted the low abundance of Delta fish species during his presentation before the State Water Resources Control Board.

"I told the State Water Resources Control Board that the numbers in the 2012 fall survey would be really bad because of the Vise on the Delta, caused by increasing exports, increasing inflows and declining outflows," said Cannon.

Conditions similar to this spurred the Pelagic Organism Decline (POD) of Delta smelt, longfin smelt, striped bass and other species that state and federal scientists documented first in 2005.

The scientists pinpointed three major factors for the unprecedented decline (1) water export increases and changes; (2) toxic chemicals; and (3) invasive species. They later added ammonia discharges as a factor in the collapse.

Cannnon said the "vise" of increasing exports, increasing inflows from upstream reservoirs and declining outflows results in less residency time of water in the Delta.

The habitat that all of the pelagic fish studied thrive in is "green water" — water that has had a chance to stay in the Delta long enough for it acquire a greenish hue because of the abundance of phyto plankton, according to Cannon. This plankton serves as the basis for the food chain that Delta smelt, threadfin shad and the other fish species thrive in.

"If water exports take all of the Delta water and the water is replaced with water from upstream reservoirs, the water doesn't have a chance to 'stew' with plankton," said Cannon. "The warm water coming downstream during the summer is lethal to the smelt. The cooler Delta water that smelt need water replaced with warm reservoir water, making conditions doubly bad for smelt."

To avoid these fish population crashes from happening in the future, Cannon recommended that the Water Board develop specific standards for inflows, outflows and exports on the Delta, according to year type.

Mike Taugher, CDFW Communications Director, responded to the release of the fall survey numbers.

"The fall midwater trawl numbers are consistent with the depressed numbers we have seen for the last decade," said Taugher. "Last year's rebound was nice but almost certainly due to wet conditions in 2011."

Bill Jennings, Executive Director of the California Sportfishing Protection Alliance, blasted state and federal agencies for allowing the Delta fish population crash to continue.

"Here we are seeing another disaster in the species studied in the fall midwater trawl surveys — and this was all predicted," said Jennings. "Species are lurking on the edge of extinction and just about everybody in the regulating agencies is to blame."