[env-trinity] The Health of the Delta Bass Fishery And the Food Chain Crash

[Daniel Bacher]

The Health of the Delta Bass Fishery And the Food Chain Crash

by Dan Bacher

The Delta black bass fishery is one of the healthiest in the country, 
judging from the latest DFG data and reports of anglers fishing the Delta. 
One question that anglers are asking is: how will the dramatic decline of 
plankton and pelagic (open water) fish that the state and federal 
governments are now studying on the Delta impact the bass population?

“The Delta has an amazing largemouth fishery, although the striped bass 
juvenile index continues to decline,” said Dennis Lee, senior fishery 
biologist for the California Department of Fish and Game. “The bass fishing 
has become better every year, based on our data regarding tournament weights 
and per hour efforts.”

In fact, as the flow regime in the Delta has changed in the past decade, the 
bass fishery has thrived. “In recent years, your chance of catching a 
largemouth on January 1 has been very good,” Lee said. “However, that wasn’t 
the case 20 †o 30 years ago when the Delta would be blown out for bass 
fishing in most places at that time of year because of high water.”

With less flow through the Delta because of increasing state and federal 
exports, there is also a chance for more weed beds to grow on the Delta, 
creating better bass habitat and fishing.

“Our tournament statistics show that the catch rates and the size of the 
bass continue to grow,” said Lee. “It’s not rocket science that the bass 
fishery is getting better – just ask any bass angler.”
>From 1986 to 2004, the mean weight of black bass weighed in tournaments rose 
from 1.68 pounds to 2.31 pounds. Likewise, the mean catch per hour increased 
from .216 in 1986 to .278 in 2004.

The total number of bass caught during the tournaments has increased from 
1986 to 2004 also. A total of 901 anglers caught 4,709 bass in 13 days of 
fishing in 1986, while 9,164 participants in 229 days of fishing caught and 
released 25,681 fish in 2004.

Interestingly, there were some notable declines in the mean catch per hour 
during the drought years of 1989 through 1993, with the lowest mean catch 
per hour reported in 1989, when only 0.106 fish per hour were landed. 
However, the fishing bounced back from 1993 to 2004.

The introduction of Florida-strain bass to the California Delta has been a 
big factor in the increase in the average size of Delta largemouths. The 
Stockton Bass Busters, in cooperation with the DFG, first transplanted 
Florida strain bass from Rancho Seco Lake in Sacramento County to the Delta 
in the early 1980’s. Stocks of tens of thousands of Floridas in Hog and 
Sycamore sloughs followed this introductory plant, according to Lee.

“In the early 1990’s, a genetic survey of Delta bass was conducted by U.C. 
Davis,” said Lee. “It showed that 15 to 20 percent of the fish exhibited 
Florida-strain characteristics.” However, Lee and others suspect that the 
increasing size of the bass indicates that there may be higher incidence of 
Florida-strain characteristics now.

“Every year the fish seem to be getting bigger and bigger,” said Lee. “In 
the 1980’s, a 6 to 7 pound fish would win the big fish category in a 
tournament. Now you see lots of tens and double digit fish in the tournament 
weigh-ins. The incidence of big fish has definitely risen."

Galen Jensen of Brentwood, a dedicated tournament angler, set the Delta bass 
record on February 10, 2002 when he caught an 18.62 pound largemouth bass in 
Old River in the South Delta. Fish in the 15 to 17 pound class have been 
reported since then, but no fish have yet eclipsed the Delta record.

While the black bass population is thriving, state and federal scientists 
have documented an alarming decline of open water pelagic species over the 
past three years. The biologists found the lowest populations ever of three 
species– Delta smelt, long fin smelt, striped bass – but what really 
surprised them was an apparent collapse of the Delta smelt, considered to be 
a hardy introduced species. Their data was backed up by reports of Delta 
commercial shad fishermen having an increasingly had time catching the 
popular bait fish.

At the same time, copepods and other plankton that forage fish feed open 
also plummeted to unheard-of levels.

Three factors are believed to contribute to the decline: (1) the impact of 
toxics, including new pesticides; (2) invasive plant and animal species and 
(3) changes in the Delta flow regime by the state and federal governments.

Environmental and fishery groups have pointed out that the massive exports 
of Delta water south through the California Water Project and the federal 
Central Valley Project are certainly the key factor in the decline, since 
three out of the last five years featured the highest Delta water export 
rates on record. As a consequence, a broad ranging coalition of groups has 
launched a letter writing campaign to the Governor, as well as filing a 
lawsuit blocking increased water exports until the problems of the Delta are 
fixed.

The recent summer tow net survey on the Delta taken is not very reassuring, 
either. “The Delta smelt index is the lowest we’ve ever seen and the 
juvenile striped bass index is about the same as last year – at a historical 
low level,” said Chuck Armor operations manager of the DFG’s Bay-Delta 
Branch. “However, we are waiting for the fall mid water trawl data to find 
more definitive information about the Delta smelt, long fin smelt, striped 
bass, threadfin shad, American shad and other pelagic species."

The DFG, in its fall survey that runs from September through November, will 
be surveying the fishery at 116 stations throughout the Delta from Suisun 
Marsh through the upper channels of the Delta “wherever we can get a trawl 
net in,” he noted. The Department has conducted these mid water trawl 
surveys since 1967, so it has years of data to compare the recent data to.

Meanwhile, the state and federal government scientists, in the cooperative 
“Pelagic Organism Decline” (POD) Program are conducting bioassays, examining 
the livers of fish, and analyzing the existing data. They are also looking 
at what pesticides are being used to get a handle on the contribution of 
toxic chemicals to the decline. They plan to have a draft plan report for 
2005 available on November 14.

“We think that we won’t find a simple answer to the reasons behind this 
decline,” Armor said. “I think it will be a messy answer with multiple 
factors causing the decline. One thing may be causing the decline in the 
spring and other factors in the fall and winter. We probably will not have 
the answers to the reasons behind the decline this year or even next year – 
it will probably take several years. For example, why aren’t the copepods (a 
form of zooplankton) in the food chain in the numbers they were until 
recently. We can’t come up with recommendations for solutions until we know 
exactly why.”

How this Delta food chain decline will impact its now robust largemouth and 
smallmouth bass populations is not known. Dennis Lee believes that 95 
percent of the bass diet is crayfish, even though they also forage on 
threadfin shad, bluegill, Delta smelt and other forage species.

Don Paganelli, fishing guide, and other veteran anglers continue to report 
good numbers of threadfin shad in the back sloughs of the Delta, such as 
Sycamore and Hog. “There was so much bait – shad – when I fished the Delta 
on August 26 that it was unreal,” said Paganelli. “Many times I witnessed 
bass in the 6 to 12 inch class boiling on the surface.”

However, in spite of the bait schools that Paganelli saw, he found something 
very troubling – he caught two 8 pound largemouths that should have been 
much heavier for the time of year he caught them, well after spawning 
season. “These fish were very thin – they should have been in the double 
digits – and I don’t know why,” said Paganelli.

The long-term consequences of the “Delta Crash” upon black bass, as well as 
striped bass, steelhead, king salmon, sturgeon, shad and catfish populations 
of Central Valley rivers and the Delta, are not known. Will the decline of 
Delta forage and pelagic species lead to a comparable crash in the black 
bass population down the line?

The answer is anybody’s guess, but the results of the studies by the 
State-Federal POD teams should isolate the factors of this decline and 
hopefully come up with a series of solutions to be immediately implemented 
before it’s too late.

For more information, call Chuck Armor of the California Department Fish and 
Game at (209) 942-6068.
However, until the problems of the Delta are fixed, it is crucial that the 
state and federal governments immediately halt all plans to divert more 
water from the Delta, including implementing the South Delta Improvement 
Project.