An Historical Review of the
Fish and Wildlife Resources of the
San Francisco Bay Area
by John E. Skinner
WATER PROJECTS BRANCH REPORT No. 1
Part 6 of 6
Striped Bass Pages 71 - 83
Striped Bass Life History Notes (Continued)
From the available data, it may be concluded that
the very young fish at first depend on the microcrustacea,
diatoms and other minute invertebrates.
From one to four inches they depend heavily on larger
crustaceans, Neomysis mercedis, Crago sp., aquatic isopods,
amphipods, and marine worms. During succeeding
years their diet becomes largely piscivorous, although
crustaceans continue to be important.
Growth. The growth rate and relationship between
age, length and weight was first worked out
by Scofield (1931) for California striped bass. Robinson
(1960) recently completed another study of the
subject to determine if any appreciable change had
occurred over the intervening 30 years. Both studies
show a rapid gain in length for the first 4 years of life
after which the rate becomes progressively less. Robinson,
however, found that growth both in length and
weight was more rapid than shown by Scofield, the
difference being about 10 percent greater length and
25 percent greater weight by the end of the 7th or
8th years of life. Difficulty in aging specimens after
their 7th year of life precluded accurate interpretations
beyond this age without a great deal of careful
study. Stripers reach a length of about 32 inches and
a weight of 14 pounds by their 9th year of life. The
maximum length attained in California may exceed 50
inches while the maximum weight may exceed 60
pounds (a 63 pound striped bass has been recorded).
Fish attaining the above dimensions are most likely 20
years of age or over. Stripers gain weight at a relatively
constant rate after their fifth year of life; the
gain may be in excess of 2 pounds per year.
Age to Maturity. Scofield (op. cit.) made a careful
study of maturing bass and came to the conclusion
that 35 percent of the females mature by their fourth
year, 87 percent by the fifth year, 98 percent spawn
in their sixth year and 100 percent thereafter. Males
mature earlier, many spawning while only 2 years old
and most by the time they are three. Morgan and Gerlach (1950) reported mature male fish at one year
of age. Males may be scarcely more than 10 inches
in length by the time they mature. Females, on the
other hand, are generally more than 18 inches long.
Artificial Propagation. In California, between 1907
and 1910, a brief attempt was made to propagate this
species artificially. A small hatchery was built on
Bouldin Island and operations were carried on for several
seasons but the difficulties encountered, particularly
the inability to collect ripe spawn, resulted in
the abandonment of operations.
On the Atlantic Coast there still exists a hatchery
at Weldon, North Carolina for this purpose.
Striped bass are extremely prolific and attempts to
propagate them artificially are unwarranted. So many
fry are produced through natural propagation that
almost any contribution from artificial sources would
be superfluous. Once established in an area any decline
in the population is most likely the result of environmental
factors rather than insufficient natural propagation.
Sources of Mortality. This phase of the life history
of striped bass requires more investigation. Information
simply is not available concerning the ages at
which various types of mortality occur. Several earlier
attempts to obtain data on angler haryest were attempted,
but these met with difficulties.
An unknown proportion of the eggs deposited by
the female are not fertilized. Losses occur while the
eggs and larvae develop in their hazardous position of
drifting in the river or tidal currents. Predation, sudden
changes in temperature, pollution, and a number
of other factors must also take a tremendous toll of
eggs and larvae. As the yolk material is used up the
larval fish must begin to fend for themselves, and it is
at this stage that perhaps the greatest losses occur.
Those which survive are continually subjected to
predation, diversions and pollution, each of which
could account for significant losses. Predation is everywhere
apparent, but losses to pollution and water diversions
occur at specific locations.
Losses at diversions are similar to those previously
described for king salmon and need not be repeated
here, except to say that the magnitude of striped bass
losses at diversions far exceeds those of any other
species in the Bay and Delta area. Some idea of the
numbers involved can be obtained from recent tests at
two major water diversions in the Delta.
The Contra Costa Steam Plant of the Pacific Gas and
Electric Company located near Antioch requires 868
cubic feet of water per second for cooling purposes at
peak capacity. Screening small fish from this amount
of water presented a formidable problem but one
which was eventually overcome by research and cooperation
between the Pacific Gas and Electric Company
and the Department of Fish and Game. This
plant alone, it was estimated, could conceivably affect
10 percent of the annual striped bass fry population
which, it will be recalled, was estimated at 35 million
fish in 1951. Fortunately, salvage operations have
greatly reduced the numbers of small fish destroyed
at the installation.
Similarly, but on a more gigantic scale, the Tracy
Pumping Plant of the Central Valley Project draws
water from Old River and pumps it into the Delta-
Mendota Canal for irrigation purposes in the San
Joaquin Valley. A very conservative estimate of fry
under the influence of this large diversion (designed to
draw 4,600 cfs at peak periods) would be 10 to 15
percent of the population each year. Research by the
Bureau of Reclamation and the Fish and Wildlife
Service in cooperation with the Department, resulted
in a revolutionary new type of salvage facility termed
the "louver facility". Up to 98 percent of fish one
inch or more in length have been successfully deflected
from the diversion by it. From March through August
of 1957, the completed structure bypassed over 1,750,-
000 striped bass, 217,800 salmon and steelhead, 1,187,-
000 catfish, and 261,800 miscellaneous fish.
Pollution affects fish in several ways: the most obvious,
of course, is the direct lethal action of toxic
substances which results in mass kills but which is
seldom detected. Small fish under the influence of
tidal currents are carried in the vicinity of toxic discharges
which they might otherwise avoid. Even the
adults are sometimes caught in particularly toxic discharges
as in the case of the Stauffer Chemical Company
fish kill in San Francisco Bay in May of 1957 and
the Napa River die-off of several years ago.
Usually, however, polluting substances destroy the
bottom fauna or food organisms upon which fish depend,
or set up a barrier in the form of odors, acidity,
temperature or some other condition which is detected
by the fish and which they avoid. The latter two are
not sources of mortality but they restrict the habitat
and result in loss to the fishery.
Predation undoubtedly causes large losses among
striped bass under 12 inches in length. After this, however,
they themselves are predators and are pretty well
removed from the forage class.
Old age, diseases, and parasites also take their toll
of fish. Little work has been done concerning the
former two. The author has observed striped bass completely
riddled with the larval form of a cestode of the
order Trypanorhynca. It is thought to be of the genus
Gymnorhynchus. Striped bass are the intermediate
host of this parasite which has as its definitive host certain
sharks, skates and rays. Another common parasite
observed was the nematode Contracaecum, of undetermined
Scofield (1929) reported injuries to striped bass
from lampreys, presumably the Pacific lamprey (Entosphenus
tridentatus). The author has observed a
large number of striped bass with lamprey scars, and
in a few instances with fairly fresh wounds. The
effects of predation by lampreys cannot be assessed at
this time without considerable conjecture; nevertheless,
it is thought that lampreys are not a particularly important
source of mortality.
Commercial exploitation was prohibited by law in
1935 largely eliminating this source of mortality.
However, studies by the writer (Skinner, 1957) from
1954 to 1957 showed that a considerable number of
striped bass were destroyed incidental to commercial
shad and salmon netting operations. At a minimal estimate,
22,000 fish weighing about 250,000 pounds were
destroyed in netting operations during the fall of 1955
and the spring of 1956. The total poundage destroyed
each year by this method could easily have amounted
to 500,000 pounds. By law, fish taken by the netters
had to be returned to the water upon removal from
the nets whether dead or alive. Legislation in 1957 prohibited
all gill and trammel netting within the Golden
Gate, thus eliminating such losses in the future.
Prior to 1935 striped bass were taken commercially.
The amount taken each year is described in an earlier
section of this report.
The next and probably the greatest single source of
mortality among legal size fish is incurred from angling.
Tagging studies aimed at measuring the exploitation
from this source have not been wholly successful.
Clark's tagging study (1934 and 1936) was not
intended for this purpose primarily and certain deficiencies
in it do not permit application of the results
to the fishery in general. He recovered about 10 percent
of the fish he tagged within one year of the date
A very intensive tagging program conducted by
Alex Calhoun of the Department of Fish and Game
was specifically designed to measure the proportion of
the population caught by anglers. It soon became apparent,
however, that the commercial gill net fishery
in the Delta and Suisun Bay region was seriously interfering
with the study. The gill netters removed the
tagged fish before the anglers had the opportunity to
catch them and furthermore, the placement of tags on
the fish was found to increase the chances of a fish
being captured by the gill nets. Other adverse factors
included the reluctance of sport and commercial fishermen
to return tags from captured fish. Because of
these conditions only the roughest sort of estimate
was possible regarding the proportion taken by anglers.
The writer made a brief study of tag returns from
the above program and concluded that the proportion
exploited by both sources, anglers and gill nets, was
in excess of 25 percent of the legal population annually.
Chadwick, (unpublished data) in a later review
estimated a minimal annual rate of exploitation of 10
percent. Anglers, of course, were presumed to catch
the greater share by quite a large margin.
Chadwick (unpublished data) initiated another tagging
program in the spring of 1958 after removal of
the gill net fishery. Preliminary analysis of the first
three years of tag returns indicate angling mortality
on the order of 20 to 30 percent annually on the population
over 16 inches in length.
In spite of all the factors acting against it, the
natural survival of this species is obviously high. The
frequency with which individuals in excess of 30 or 40
pounds (over 15 years of age) are encountered lead
to the conclusion that natural mortality is low.
COMMENTS REGARDING CHANGES IN THE FISH AND WILDLIFE
RESOURCES OF THE BAY AREA
Striped Bass - Page 169
Generally speaking, this fishery has remained relatively
stable. The species was completely removed
from the commercial category in 1935 and since then
has been subjected to hook-and-line fishing only, except
for fish which were taken incidentally with shad
and salmon by the gill net fishery. The sport fishery
is so intense it is believed that up to 25 percent of all
legal-sized fish are removed from the fishery each year.
A review of the catch records and other pertinent
data revealed a decline in the fishery from 1944
through 1955. As a consequence, further restrictions
in size and bag limits were put into effect to bring
the fishery into balance. This appears to have been
Under present conditions, it appears that the sport
fishery is now exerting sufficient pressure to have a
definite influence on striped bass stocks. The governing
factor, however, lies in the change in environmental
conditions. These have been modified so
greatly over the past fifty years that there has been
an appreciable loss in the total habitat available to
At least three adverse factors, excluding angling, are
affecting the striped bass population: reclamation,
water development projects, and pollution. It would
be next to impossible to evaluate the relative importance
of each. Reclamation, many years ago, resulted
in extensive habitat changes which removed rich nursery
grounds. Water development projects have modified
temperature, flow, and salinity patterns in the
Delta and in spawning areas, and numerous diversions
take a heavy toll of fish. Pollution has resulted in an
extensive loss of habitat, destruction of forage organisms,
and, frequently, in the outright killing of the fish
The absence of striped bass in many areas of the
Bay may be taken as rather clear evidence of pollution.
South San Francisco Bay in particular can be cited,
and there are other once-favorable localities which are now similarly devoid of striped bass.
Part 6 of 6 |
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Calhoun, A. J.
1949 California Striped Bass Catch Records From the Party
Boat Fishery; 1938-1948. California Fish and Game,
Vol. 35, No. 4, pp. 211-253.
1950 California Angling Catch Records from Postal Card
Surveys: 1936-1948 With an Evaluation of Postal Card
Non-response. California Fish and Game, Vol. 36, No.
3, pp. 177-233.
1951 California State-Wide Angling Catch Estimates for
1949. California Fish and Game, Vol. 37, No. 1, pp.
1952 Annual Migrations of California Striped Bass. California
Fish and Game, Vol. 38, No. 3, pp. 391-403.
1953a. State-Wide California Angling Estimates for 1951. California
Fish and Game, Vol. 39, No. 1, pp. 103-113.
1953b. Distribution of Striped Bass Fry in Relation to Major
Water Diversions. California Fish and Game, Vol. 39,
No. 3, pp. 279-299.
1957 Striped Bass Fishing Map (Revised by John E. Skinner).
California Department of Fish and Game.
Calhoun, A. J., and John E. Skinner
1954 Field Tests of Stainless Steel and Tentalum Wire with
Disk Tags on Striped Bass. California Fish and Game,
Vol. 40, No. 3, pp. 323-328.
Calhoun, A. J., and C. A. Woodhull
1948 Progress Report on Studies of Striped Bass Reproduction
in Relation to the Central Valley Project. California
Fish and Game, Vol. 34, No. 4, pp. 171-187.
1950 Striped Bass Reproduction in the Sacramento River
System in 1948. California Fish and Game, Vol. 36, No.
2, pp. 135-145.
Clark, G. H.
1929 Sacramento-San Joaquin Salmon (Oncorhynchus tshawytscha)
Fishery of California. California Fish and
Game, Fish Bulletin No. 17.
1932 The Striped Bass Supply of California, Past and Present
California Fish and Game, Vol. 18, No. 4, pp.
1933 Fluctuations in the Abundance of Striped Bass (Roccus
lineatus) in California. California Department of Fish
and Game, Fish Bulletin No. 39.
1934 Tagging of Striped Bass. California Fish and Game,
Vol. 20, No. 1, pp. 14-19.
1936 A Second Report on Striped Bass Tagging. California
Fish and Game, Vol. 22, No. 4, pp. 272-283.
1938 Weight and Age Determination of Striped Bass. California
Fish and Game, Vol. 24, No. 2, pp. 176-177.
Cole, Charles E.
1930 Angling for Striped Bass. California Fish and Game,
Vol. 16, No. 4, pp. 286-290.
Craig, J. A.
1928 The Striped Bass Supply of California. California
Fish and Game, Vol. 14, No. 4, pp. 265-272.
1930 An Analysis of the Catch Statistics of the Striped Bass
(Roccus lineatus) Fishery of California. California
Department of Fish and Game, Fish Bulletin No. 24.
Hatton, S. Ross
1940. Progress Report on the Central Valley Fisheries Investigations,
1939. California Fish and Game, Vol.
26, No. 4, pp. 334-373.
Jackson, H. W. and R. E. Tiller
1952 Preliminary observations on spawning potential in
striped bass (Roccus saxatilis). Maryland Dept. Res.
and Ed., Pub. 93, pp. 1-6.
Johnson, W. C, and A. J. Calhoun
1952 Food Habits of California Striped Bass. California
Fish and Game, Vol. 38, No. 4, pp. 531-533.
Morgan, Alfred R. and Arthur R. Gerlach
1950 Striped Bass Studies on Coos Bay, Oregon in 1949 and
1950. Oregon Fish Commission, Contribution No. 14.
Pearson, John C.
1938 The Life History of the Striped Bass or Rockfish,
(Roccus saxatilis) (Walbaum). U. S. Department of
Commerce Bureau of Fisheries, Vol. XLIX, Bulletin
Raney, Edward C, Ernest F. Tresselt, Edgar H. Hollis, V. D.
Vladykov and D. H. Wallace
1952 The Striped Bass (Roccus saxatilis). Bulletin of the
Bingham Oceanographic Collection, Vol. 14, Article 1.
Scofield, N. B.
1910 Notes on striped bass in California. Biennial Report,
Calif. Board of Fish and Game Commissioners for
1909-1910, pp. 104-109.
1936 Food of the Striped Bass. California Fish and Game,
Vol. 22, No. 4, pp. 261-270.
Skinner, John E.
1955a. California State-Wide Angling Estimates for 1953.
California Fish and Game, Vol. 41, No. 1, pp. 19-32.
1955b. Observations on the Shad Gill Net Fishery in 1954.
California Department of Fish and Game, Inland Fisheries
Branch, Administrative Report 55-3.
1957a. Incidental losses of Striped Bass in the Sacramento
River Gill Net Fisheries for Shad and Salmon. California
Department of Fish and Game, Inland Fisheries
Branch, Administrative Report 57-2.
1957b. Status of the Striped Bass—Sturgeon Study and Suggestions
for its Future. California Department of Fish
Fish and Game, Inland Fisheries Branch, Administrative
Report No. 57-11.
Smith, Hugh M.
1895 The Striped Bass History and Results of Introduction.
U. S. Fish Commission Bulletin, Vol. 15, pp. 449-458.
1947 Spawning Habits of the Striped Bass (Roccus saxatilis)
in California Waters. California Fish and Game,
Vol. 33, No. 2, pp. 97-101
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