[env-trinity] The Health of the Delta Bass Fishery And the Food
danielbacher at hotmail.com
Mon Sep 5 17:46:28 PDT 2005
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 wasnt
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. Its 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 1980s. Stocks of tens of thousands of Floridas in Hog and
Sycamore sloughs followed this introductory plant, according to Lee.
In the early 1990s, 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 1980s, 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
The recent summer tow net survey on the Delta taken is not very reassuring,
either. The Delta smelt index is the lowest weve 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 DFGs 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 wont 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 arent the copepods (a
form of zooplankton) in the food chain in the numbers they were until
recently. We cant come up with recommendations for solutions until we know
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 dont 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 anybodys 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 its 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
More information about the env-trinity