29

NOAA Technical Report NMFS 29

Prevalence, Intensity,

Longevity, and Persistence

of Anisakis sp. Larvae and

Lacistorhynchus tenuis

Metacestodes in

San Francisco Striped Bass

Mike Moser, Judy A. Sakanari, Carol A. Reilly,

and Jeannette Whipple

April 1985

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service
NOAA TECHNICAL REPORTS NMFS

The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance and

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The NOAA Technical Repon NMFS series was established in 1983 to replace two subcategories of the Technical Reports

series: "Special Scientific Repon-Fisheries" and "Circular." The series contains the following types of repons: Scientific

investigations that document long-term continuing programs of NMFS, intensive scientific reports on studies of restricted

scope, papers on applied fishery problems, technical repons of general interest intended to aid conservation and management,

repons that review in considerable detail and at a high technical level cenain broad areas of research, and technical papers

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Copies of NOAA Technical Report NMFS are available free in limited numbers to governmental agencies, both Federal

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copies may be obtained from: U.S. Depanment of Commerce, National Technical Information Service, 5285 Port Royal Road,

Springfield, VA 22161.
NOAA Technical Report NMFS 29

Prevalence; --Intensi.ty; . )" '·1 ," .. '.... -. '

Lori'gevity, 'and Persistence

P. of Anis'akis~ sp. 'Larvae.. and

."Lacisto'lhyh'chus teiniis" .,

Metcicesfodes. in ' ; ."

San Francisco Striped Bass

Mike Moser, Judy A. Sakanari, Carol A. Reilly,

and Jeannette Whipple

April 1985

u.s. DEPARTMENT OF COMMERCE

Malcolm Baldrige, Secretary

National Oceanic and Atmospheric Administration

John V. Byrne, Administrator

National Marine Fisheries Service

William G. Gordon, Assistant Administrator for Fisheries
The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any propriety product or proprietary material mentioned

in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales J'romotion which

would indicate or imply that NMFS approves, recommends or endorses any

proprietary product or proprietary material mentioned herein, or which has

as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication.
CONTENTS

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

Materials and methods .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

Collection I

Aging.................................................................................................. I

Diet analysis .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

Statistical analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Serial infections 1

Longevity and persistence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Diet analysis .. . . . . . . . . . . . . . .. 2

Anisakis sp. 2

Host reaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Prevalence and intensity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Serial infection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Longevity and persistence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Lacistorhynchus tenuis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Host reaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Prevalence and intensity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Persistence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Other parasites and a tumor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Literature cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figures

1. Stomach content analysis of striped bass in the three major age groups in winter, spring, and summer. . . . . . . . . . . . . . . . . . . . . 2

2. Cross section of posterior end of stomach with embedded larval nematodes 2

3. Prevalence and intensity of larval nematodes compared with age of host. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

4. Anisakis sp. larvae encapsulated in fibrous "raft" 3

5. Prevalence and intensity of metacestodes compared with age of host. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

6. Tumor, attached to mesenteries, cross section 3

iii

Prevalence, Intensity, Longevity, and Persistence of

Anisakis sp. Larvae and Lacistorhynchus tenuis

Metacestodes in San Francisco Striped Bass

MIKE MOSER, JUDY A. SAKANARI, CAROL A. REILLY,! and

JEANNETTE WHIPPLE2

ABSTRACT

Thirteen hundred and seventy-three striped bass, Marone saxatilis, were collected from the San Francisco

Bay-Delta area to correlate host diet with parasitic infections and to determine the prevalence, intensity, longevity, and persistence of larval Anisakis sp. nematodes and the metacestode Lacistorhynchus tenuis. There is an increase in the prevalence and intensity of AIli.<akis sp. and in the intensity of L. tenuis with increase of age of tbe

host. These increases are probably ..elated to the diet and the persistence of tbe parasites. The infections of both

species are overdispersed. San Francisco Bay striped bass are an incompatible host for both species of parasites.

Degenerated Anisakis sp. will remain in lhe host for at least 8 months and L. tenuis metacestodes for 22 months.

The occurrence of several other species of parasites and a tumor are also reported.

INTRODUCTION

Striped bass, Morone saxatilis, is a popular sportfish in the San

Francisco Bay, CA, area. Anglers have often reported the presence'

of parasites in the mesenteries and muscle of striped bass and

questioned the public health aspects of the parasitic infections.

The purpose of this study was to determine the prevalence (no.

hosts infected/no. hosts examined), intensity (total no. parasite's/

no. infected hosts), longevity (time parasites remain alive), and

persistence (time degenerated parasites are detectable) of the two

most c0mmonly seen parasites: the metacestode Lacistorhynchus

tenuis (Cestoda) and the larval nematode Anisakis sp. (probably A.

simplex).

MATERIALS AND METHODS

Collection

Thirteen hundred and seventy-three striped bass were collected

from the San Francisco Bay-Delta area between June 1979 and

December i 983 by hook and line, gill net, and otter trawl. Fish

were frozen or Formalin-fixed and autopsied for parasites and

stomach content analy~es at Long Marine Laboratory, University

of California, Santa Cruz.

Aging

The age of the fish was determined by scale ring counts by the

California Department of Fish and Game and the use of growth

curves.

ICoastal Marine Studies, University of California, Santa Cruz, Santa Cruz, CA

95064.

'Physiological Ecology Investigations, Southwest Fisheries Center Tiburon

Laboratory, National Marine Fisheries Service, NOAA, Tiburon, CA 94920.

Diet Analysis

The stomach contents of the fish were analyzed to determine

possible correlations between diet and parasite infections.

Stomach contents of 831 striped bass collected between January

and September 1981 from San Pablo Bay and Suisun Slough were

examined for possible intermediate hosts. The Index of Relative

Importance (IRI) of food items was determined by methods suggested by Cailliet (1976). The young-of-the-year (YOY) and most

of the l-yr-olds had similar diets, hence were combined for

analysis. The age groups for diet analysis were: YOY and l-yr-old

(10 to 230 mm SL); subadult females and adult males (2 to 3 yr);

am! adults (4+ yr).

Statistical Analysis

The coefficient of dispersion (overdispersed distribution) was

determined to indicate possible clumping in parasite distributions,

hence the possible need for nonparametric analysis (Sokal and

Rohlf 1969). Within each age class seasonality did not significantly change the prevalance or intensity of the parasitic infections. Therefore, all seasons were combined within each age class

(ANOYA, regression analysis).

Serial Infections

Serial'infections were performed to determine whether nematode larvae can be transferred from fish to fish. The striped bass

used in both infection experiments were YOY hatchery fish provided by the California Department of Fish and Game, Elk Grove,

CA. The third stage larval Ar;isakis sp. used were from bocaccio,

Sebastes paucispinis. The fish were force-fed (Wootten and Smith

1975) with washed iarvae (Tanaka and Torisu 1978). Fifty larvae

were fed to each of six striped bass. As a control, four YOY

yellowtail rockfish, Sebastes flavidus, were infected in a similar

manner.
Longevity and Persistence

Striped bass collected from the field were observed to have

degenerated larval nematodes in their mesenteries and tissues. The

purposes of this experiment were to determine how long the larval

Anisakis sp. remain alive in striped bass, therefore potentially

harmful to humans, and to determine the persistence of dead larvae in the mesenteries and muscle. The third stage Anisakis sp. larvae used were prepared as above but were from sablefish, Anoplopoma fimbria. To insure that all fish were infected with equal

numbers of larvae, 25 larvae were inserted into the coelomic cavity through a small cut on the sides of 178 striped bass. This wound

was sealed with a nontoxic biological glue, Histoacryl (Tri-Hawk,

Los Angeles, CAl. Previous tests showed that striped bass reacted

similarly to larvae infected by this technique, to those force-fed,

and to those seen in field fish. The hosts were periodically autops'ed during a 33-wk period.

RESULTS

Diet Analysis

The fullness of the stomachs and the percent IRI for the dominant food item or items are given for each age class. No stomachs

contained larvae or metacestodes (Fig. I).

Anisakis sp.

Host reaction.-The larval Anisakis from field fish were found

on the mesenteries and internal organs. Rarely were they found in

the muscle tissue. Most larvae were dead or degenerating with

dark brown cuticles. The larvae were often seen as solid, round

masses of fibrous tissue. When several larvae were in close proximity in the mesenteries, they were often encapsulated to form a

fibrous "raft." In field fish with high intensity infections,

numerous degenerated larvae were found embedded in the

posterior end of the stomach (Fig. 2).

Prevalance and intensity.-The prevalence and intensity of

larval nematode infections in striped bass begin to increase at 4 yr

and continue to increase throughout the life uf the host. The mean

to variance ratios (year classes 3 to 8+ are: 1.3,14.2,58.8,33.7,

<19.9, 39.5, respectively) show the infections to be increasingly

overdispersed with time (Fig. 3).

Serial infection.-Autopsies showed that after 5 wk, two of six

striped bass were infected by one and four larvae. respectively.

Figure 2.-Cross section of posterior end of stomach with embedded larval

nematodes.

I 60 [ 60 0 '"

u

z ·40 40 t:: '"...J <n

z

'" '" l- ll::

Q.

20 20

-- ace Ii Years 'lOY 2 3 4 5 6 7 8

748 44 79 76 133 72 70 37 37

Figure 3.-Prevalence and intensity of larval nematodes compared with age of

host. Bar =standard error.

Although the larvae from the striped bass responded weakly to

tactile stimuli, the cuticle had darkened, resembling the dead larvae recovered from field-captured striped bass. In contrast, three

of the four rockfish were infected wIth an average of four larvae.

The larvae from the rockfish were more active, and the cuticle

was flesh colored, similar to larvae from field-collected Sebastes

paucispinis and other fish hosts.

Figure I.-Stomach content analysis of striped bass in the three

major age groups in winter (W), spring (Sp), and summer (Su).

Neomysis sp

ll::

10°[[I-'1 50 I

a'i 0

c~IOot=o=J :; 50 LL

g!!. 0

w Sp Su

N= 109 :44 269

YOY-Iyr

2

Neomysis sp.

- 100 til]-I 50 i

a'i o

100 Fishes

:so1

O~,

100}

~:CLLJ w Sp Su

12 17 12

2-3 yr

100[L[]FiShes

50

o 5mol: Crustaceans

1::]1.-_-'-= __'--__

100b 50 .

o w Sp Su

28 212 23

4+ yr
Figure 5.-Prevalence and intensity of metacestodes compared with age of host.

Bar = standard error.

(this study); Digenea-Stephanostomum tenue (D. Woodbury footnote 3), Lepocreadium californianum (Edwards and Nahhas 1968);

Monogenea-Cleidodiscus pricei (Hensley and Nahhas 1975);

Nematoda-Thynnascaris brachyurum (as Contracaecum b.,

Hensley and Nahhas 1975), Spiroxys sp. larva (Hensley and

Nahhas 1975), and Phocanema sp. larvae, in mesenteries, (this

study); a tumor, in coelom, (this study, Fig. 6, National Museum of

Natural History-Registry of Tumors in Lower Animals (NMNHRTLA) #3173).

20

00

60 0

>-

>- 60 U)

z

w

>- 40

20

140

120

6 7 >8

70 37 37

I

Fl

100

Ylar. YOY 2 3 4 5

N 748 44 79 76 133 72

60

w

(.)

z

W

...J

40

w

a:

n.

I 60

Figure 4.-Anisakis sp. larvae encapsulated in fibrous "raft."

Lacistorhynchus tenuis

Longevity and persistence.-At the end of 2 wk most larvae

had been encapsulated into a fibrous "raft." In the following 31

wk, in addition to the "raft," one to five larvae were recovered in

the coelom or attached to the mesenteries. These larvae usually

responded weakly to tactile stimuli, but became progressively

darker and weaker with time (Fig. 4).

Host reaction.-Moser, Sakanari, Wellings, and Lindstrom

(1984) described the inflammatory response of the striped bass to

these "rafts." The metacestodes from field fish appeared degenerated. The outer surface of the blastocyst was brown and the

metacestode was a hardened mass. Often, the metacestodes,

similar to the nematode larvae, were encapsulated into fibrous

"rafts. "

Prevalance and intensity.-During the first year the prevalence of larval cestode infections reached 81.6% and remained

approximately at this level throughout the year. However, the

mean intensity of infection slowly increases with the age of the

host. The mean to variance ratios (age classes YOY to 8+ are:

14.4,23.2,38.9,9.2,48.6,36.7,59.3,51.2, 73.0, respectively) indicate the infections were increasingly overdispersed with time

(Fig. 5).

Figure 6.-Tumor aJ allached to mesenteries, bJ cross section.

DISCUSSION

Persistence.-Four field fish kept in the laboratory for 22 mo

still retained their dead metacestodes and "rafts."

Other Parasites and a Tumor

Occasionally other helminth parasites were encountered during

autopsies. However, because of the overall goal of this study and

the method of preservation of field fish, no attempt was made to

quantify these helminths. Parasites reported from the San Francisco Bay-Delta include: Acanthocephala-Southwellina (D.

WoodburyJ); Cestoda-Tetraphyllidae larvae, in mesenteries,

3D. Woodbury, Seasonal Aide, California Department of Fish and Game, 203 Tall

Trees Drive, Vallejo, CA 94589, pers. commun. March) 983.

The food habits of San Francisco Bay-Delta striped bass have

been reported by Turner and Kelley (1966), Thomas (1967), Orsi

(1971), Moriguchi (1973), Moyle (1976), and Orsi and Knutson

(1979). The present study and the above reports show that YOY

consume primarily shrimp (Neomysis sp. and Crangon sp.), amphipods (Corophium sp.), and copepods. By the end of the first year

the fish begin to switch from feeding on invertebrates to eating

fish (striped bass, shad, salmon, flatfish, herring, perch, bait). This

trend continues in the subadults. Although adults are primarily

piscivorous, striped bass continue to eat some invertebrates, such

as crabs. The adults, and perhaps the subadults, reduce their feeding in the spring and early summer during the spawning season.

The life cycle of Anisakis sp. usually includes a marine crustacean as the first intermediate host, a fish or squid as the second

host, and a marine mammal as the definitive host. The larva of

Anisakis sp. is well known as a potential hazard to human health if

3
consumed in raw or improperly prepared seafood (Moser, Love,

and Sakanari 1984). San Francisco Bay striped bass infected with

larval Anisakis do not appear to be a major health hazard. Rarely

were these larvae found in the muscle tissue. In addition, most of

the larvae degenerate in the body cavity after a few weeks. The

results of this study suggest that some degenerating larvae and the

fibrous "rafts" can persist in striped bass for at least 33 wk. This

slow turnover rate of larvae probably contributes to the increase in

intensity of infection with time.

Wootten and Smith (1975) showed that trout can be serially

infected with Anisakis sp. larvae from herring. Many of the fish

consumed by striped bass are infected by Anisakis sp. larvae (Love

and Moser 1983). The serial infection experiments with Anisakis

sp. larvae may explain the increase in prevalence and intensity as

striped bass become more piscivorous at 4 yr. Although numerous

fibrous "rafts" were found in the mesenteries and next to the

peritoneum of field fish, they did not form open lesions as described for the metacestodes of L. tenuis in San Francisco Bay striped

bass (Moser, Sakanari, Wellings, and Lindstrom 1984).

The life cycle of Lacistorhynchus tenuis, although not completely described, most probably includes the adult in an elasmobranch, such as the leopard shark, Triakis semifasciata, common to

San Francisco Bay, the procercoid in a crustacean, and the metacestode in fish. Lacistorhynchus tenuis metacestodes have been

reported worldwide from more than 60 species of hosts (Moser

1983), including striped bass from the east coast and other San

Francisco Bay fish, with no apparent harm to the host. However,

Moser, Sakanari, Wellings, and Lindstrom (1984) have shown

that these metacestodes are pathological to striped bass found in

the San Francisco Bay-Delta area.

The sharp rise in prevalence of L. tenuis metacestodes in the

l-yr-olds may be related to the movement of this age class from

the Delta area into San Francisco Bay where they are more 'likely

to encounter the infected intermediate hosts. The continued increase in the intensity of metacestodes through time may reflect

both the acquisition of new metacestodes and their persistence in

the host. Preliminary studies (Sakanari, Moser) suggest that metacestodes of L. tenuis can be transfered serially from white croaker,

Genyonemus lineatus, to striped bass. These studies suggest that

the prevalence of metacestodes from the YOY to the I yr class

may also be related to increased piscivory. The increased clumped

distribution of parasites with the age of the host may indicate

striped bass vary in their susceptibility to these parasites. Some

hosts may eliminate the parasites before they can become embedded in the mesentaries or muscle tissue. Striped bass were introduced into San Francisco Bay from the east coast approximately

100 yr ago. The type of incompatibility shown here has not been

described between east coast striped bass and their helminth

parasites. Current studies are investigating the possibility that the

west coast striped bass are immunologically incompatible with the

indigenous strain of parasite.

ACKNOWLEDGMENTS

We thank the staffs at Marine Studies, University of California,

4

Santa Cruz, and the National Marine Fisheries Service, Tiburon,

CA; Marvin Jung, State Water Resources Control Board; Frank

Fisher and the California Department of Fish and Game, Kinnetics Laboratory; Elmer Noble, University of California, Santa Barbara; James Berry, Scripps Institute of Oceanography, La Jolla,

CA; Donald Gruber, Pinole, CA; Thomas Tucker, Steinhart Aquarium, California Academy of Sciences.

LITERATURE CITED

CAILLlET, G. M.

1976. Several approaches to the feeding ecology of fishes. First Pac. N.W.

T~ch. Workshop. Sess. 1. Workshop Proc., Astoria, Oreg., October 13-15,

1976,

EDWARDS, S. R., and F. M. NAHHAS.

1968. Some endoparasites of fishes from the Sacramento-San Joaquin Delta,

California. Calif Fish Game 54:247-256.

HENSLEY, G. H., and F. M. NAHHAS,

1975. Parasites of fishes from the Sacramento-San Joaquin Delta, California,

Calif. Fish Game 61 :20 1-208.

LOVE, M. S., and M. MOSER.

1983. A checklist of parasites of California, Oregon, and Washington marine

and estuarine fishes. U.S. Dep. Commer., NOAA Tech. Rep. NMFS SSRF777, 576 p.

MORIGUCHI, M. N.

1973. Food habits of the striped bass, Roccus saxalilis, (Walbaum) in San

Francisco Bay with notes on the major areas of the fishery. M.A. Thesis,

San Francisco State Univ., San Francisco, CA, 61 p.

MOSER, M.

1983. Parasites of San Francisco Bay-Delta area stripped bass (Morone

saxatilis) and other San Francisco Bay fishes. Final Rep., Calif. State Water

Res. Control Board, Sacramento, CA, I 14 p.

MOSER, M., M. LOVE, and 1. SAKANARI.

1984. Common parasites of California fishes. Calif. Dep. Fish Game, 20 p.

MOSER, M., J. SAKANARI, S. WELLINGS, and K. LINDSTROM.

1984. Incompatibility between San Francisco striped bass, Marone saxa/ilis

(WalbaumJ, and the metacestode, Lacislorhynchus lenuis (Beneden 1858).

1. Fish Dis. 7:397 -400.

MOYLE, P. B.

1976. Inland fishes of California. Univ. Calif. Press, Berkeley, 405 p.

ORSI, J. J.

1971. The 1965-1967 migrations of the Sacramento-San Joaquin Estuary

striped bass population. Calif Fish Game 57:257-267.

ORSl, J. J.. and A C. KNUTSON.

1979, The role of mysid shrimp in the Sacramento-San Joaquin estuary and

factors affecting their abundance and distribution. In T. J. Conomos (editor),

San Francisco Bay: The urbanized estuary, p. 401-408. Pac. Div.lA.A.A.S.,

San Francisco State Univ., CA, June 12-16, 1977.

SOKAL, R. R., and F. J. ROHLF.

1969. Biometry. The principles and practice of statistics in biological

research. W. H. Freeman and Co., San Francisco, CA, 776 p.

TANAKA, 1., and M. TORISU.

1978. Anisakis and eosinophil. I. Detection of a soluble factor selectively

chemotactic for eosinophils in the extract from Anisakis larvae. J.lmmunol.

120:745-749.

THOMAS, 1. L.

1967. The diet of juvenile and adult striped bass, Roccus saxalilis, in the

Sacramento-San Joaquin River system. Calif. Fish Game 53:49-62.

TURNER, J. L., and D. W. KELLEY.

1966. Ecological studies of the Sacramento-Joaquin Della. Calif. Dep, Fish

Game, Fish Bull. 136, Part II, Fishes of the Delta, 168 p.

WOOTTEN, R., and J. w. SMITH.

1975. Observational and experimental studies on the acquisition of Anisakis

sp. larvae (Nematoda: Ascaridida) by trout in fresh water. Int. J. Parasitol.

5:373-378.