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Parasites as Indicators of English Sole
(Parophrys vetulus) Nursery Grounds
a
Robert E. Olson & Ivan Pratt
a
a
Department of Zoology, Oregon State University, Marine Science
Center, Newport, Oregon, 97365, USA
Available online: 09 Jan 2011
To cite this article: Robert E. Olson & Ivan Pratt (1973): Parasites as Indicators of English Sole
(Parophrys vetulus) Nursery Grounds, Transactions of the American Fisheries Society, 102:2, 405-411
To link to this article: http://dx.doi.org/10.1577/1548-8659(1973)102<405:PAIOES>2.0.CO;2
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Parasites as Indicators ot• English Sole
(Parophrys vetulus) Nursery Grounds
ROBERT E. OLSON AND IVAN PRATT
Department of Zoology, Oregon State University, Marine Science Center,
Newport, Oregon97365
Downloaded by [Oregon State University] at 13:09 17 October 2011
ABSTRACT
Juvenile English sole (Parophrys vetulus) utilize Yaquina Bay, Oregon as a nursery during
at least a portion of their first year of life, but the possibility of the existenceof additional
nurserygroundsoffshorehas not previouslybeen examined. During 1971, young-of-the-yearfirst
appearedin Yaquina Bay in February, were abundantfrom April to September,and most emigrated to offshore areas in October.
Examinationof English sole,collectedboth in the estuaryand offshore,revealed certain parasitesthat appearedto be acquiredby the fish only while in the estuary. The acamhocephalan
Echinorhynchuslageniformisproved useful in determiningthe extent of estuarineutilization.
The incidence of infection in bay fish before emigration (29.9%) was similar to the incidence
in 0-groupEnglish sole collectedoffshoreafter emigration (28.5%). This result suggeststhat
there was little or no influx of young from other than estuarinenurserygroundsto the offshore
studyarea and that on the Oregoncoast,estuariesare very likely the exclusivenursery grounds
for thisspecies.Otherparasiteswerenot usefulin determiningthe extentof estuarineutilization,
but two, the nematodePhilometraamericanaand a microsporidan
Glugea sp., were considered
to be indicatorsof residencein the upper estuary. The trematodeZoogonusdextrocirrusand
metacercaria
of the trematodeOtodistomum
veliporumwere found almostexclusively
in fish
collectedoffshore,indicatinglittle or no back-and-forth
movementbetweenestuaryand open
ocean.
we have attemptedto apply parasitological
informationto relativelylocal movements
of
Englishsole, betweenthe estuaryand the
nearbyopenocean.A studyof this typehas
recentlybeen completedin Scotlandwhere
INTRODUCTION
A major portionof the UnitedStatescommercial fishery catchis composedof species
that spendat leasta part of their liveswithin
estuaries(McHugh, ]966). AlthoughEnglish
sole (Parophrysvetulus)are knownto utilize Gibson (1972) traced movements of the
Yaquina Bay, Oregon as a nursery during at flounderPlatichthys]lesususingparasitesas
least a portion of their first year of life
(Westrheim,]955), the possibleutilizationof
the shallownear-shoreareasof the open coast
by the 0-groupage classhas not been examined,and the extent to which it depends
upon the estuarinenursery groundshas not
tags.
The objectiveof our study was to find
parasitesof juvenilesthat have life cycles
operatingonly in the estuaryand to usethese
parasitesas tags to indicate that the host has
spentsometime in the estuary.In this man-
bccn determined. It has been observed that, ner, we expectedto obtain some measure of
off of the northernOregon-southern
Washing- the proportionof juvenilesthat use the estuton coast,individualslessthan 180 mm long ary as a nursery and indirectly,to determine
nurserygroundsexist
(age-I+ or less) are most commonlyfound whethernon-estuarine
in depths of 36 to 53 m and that those in the vicinity of Yaquina Bay.
less than ]00 mm long arc rare (Demory,
]971 and RobertL. Demory,]972, personal
STUDY
AREAS
AND
METHODS
Accordingto Ketchen(1956) the nursery
grounds
of English sole in Hecate Strait,
Parasitological
data havebeenusedto proBritish Columbia are shallow (less than 60
vide information on the movements and migrationsof fish hostsby a numberof investi- m), sandyregionsof coastline.The Oregon
gatorsincludingSindermann(1961), Kabata coast consists of extensive areas that fit this
(1963) and Margolis (1965). Althoughthese description;there are miles of sandybeach
studieswere primarily concerned
with move- brokenby numerousheadlands,estuaries,and
mentsoccurringover wide geographicalareas, bays. The YaquinaBay estuary(Fig. 1) is
communication).
4O5
406
TRANS. AMER. FISH. SOC., 1973, NO. 2
of the morecommonlyoccurringparasites,we
selectedthe gills, fins, musculature,
stomach
and intestine for routine examination.
Whole
mounts of trematodes,cestodes,and Acantho-
cephalawere preparedafter fixation in AFA
and staining in Semichon'sacetocarmine.
Nematodeswere fixed in 70% ethyl alcohol
containing5% glycerineand clearedin lactophenol.Copepods
werepreserved
andstudied
in 70% ethyl alcohol, and protozoanswere
studied alive in wet mounts.
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FIGURE1.--Yaquina Bay showinglocation of sampling stations.
After the more commonlyoccurringparasites had been identified, most could be rec-
ognizedalive, andtheir presence
wasrecorded
without examinationunder the high power
a drownedriver valleywith an area of ap- microscope.Thosethat couldnot be readily
proximately11.7 km• the bulk of which is identified while alive were identified only
in the lower one-thirdwhere the estuaryis after permanentpreparationswere examined
up to 3.2 km wide (Zimmerman,1972).
under a microscope.
Sampleswerecollected
with a 16-footsemiRESULTS
AND
DISCUSSION
balloontrawl. The body of the net consisted
of 3.8-cm mesh (stretch measure), the cod
end of 3.2-cm stretch mesh, and the liner of
1.3-cm mesh netting. Although this small
trawl may have been somewhatselectivefor
smaller fish, larger flatfish were commonin
samplesand the proportionof smallto large
Englishsolewasbelievedto reflectthe relative
abundanceof small fish in the area sampled.
We collectedoceansamples
in depthsof 10
to 80 m (1 to 16 km offshore) by trawling
for 20 minutesand collectedbay samplesat
threestationsnear buoys15, 29 and 39 (B15,
B29 and B39, Fig. 1), by trawling for 10
minutes. Weather and sea conditions offshore
and tidal conditionsin the bay made uniform
samplingdifficult. Nevertheless,
the catchper
unit effort was consideredto give an indication of relative abundance.Bay samples
were collectedat low tide, usually the lowest
daylighttide of the month. In no casewas
the interval of time betweenmonthly collections lessthan 15 days.
A numberof fish from each samplewas
measured
to the nearest millimeter
and as
Englishsolespawningbeginsin November,
is greatestin Decemberand January,and is
essentially
completeby March althoughsome
spawningmay continueinto May andpossibly
longer (Harry, 1959). Spawningoccursin
ill-definedareas off Oregon and young fish
are apparently transported toward shallow
water either as pelagiceggsor newlyhatched
larvae (Robert L. Demory, 1972, personal
communication).Westrheim(1955) reported
that Englishsole in Yaquina Bay reacheda
modal size of 140 mm after 1 year. Studies
conductedin Washington(Van Cleve and
E1-Sayed,1969) and in California (Smith
and Nitsos, 1969) indicated that first year
growth could range from 135 to 170 mm.
Based on English sole age and growth
studiesand on our length-frequency
data, offshorefish 140 mm or lessin total lengthwere
consideredto be in their first year of life
(0-group). Althougha few individualsin
thissizegroupmayhaveenteredtheir second
year (age I), this was of no concernsince
ourprimeinterestwasin fishthathadrecently
emigratedfrom the bay, regardless
of precise
many as was practicablewere examinedfor
parasiteswith the aid of a dissecting
micro- age.
scope.Most fish were examinedfresh; those
JuvenileEnglish sole were capturedin
that died beforereturn to the laboratorywere YaquinaBay during all monthsof the year
frozen for later examination. After prelimi- (Fig. 2). They were most abundantfrom
nary observations
to locatethe infectionsites May throughSeptemberwith lessernumbers
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OLSON AND PRATT--ENGLISH
SOLE NURSERY GROUNDS
407
bay washeavyin Octoberand wasessentially
completeby November(Table 1).
Catch-per-unit-effort
data alsoindicatethat
the lower estuary (B15) is utilized by considerablygreaternumbersof 0-groupEnglish
solethanis the upperestuary(B29 and B39)
andthattheyoungfishdo not reachthe uppermost area (B39) nntil Jnly (Table 1).
Reasonsfor the greater concentrationof
English sole in the lower estuary were not
examined;however,the physicalcharacteristic
that most likely determinesthe distribution
of thesefish within the estuaryis salinity.
Salinities in Yaquina Bay fluctuate most
widely during the winter monthswhenfreshwater runoff is high. Accordingto Zimmerman (1972) surfacesalinitiesat station B15
can vary from 27;, in winter to 35½•in summer and bottom salinities from 25 to 35%•.
In theupperestuary(B29 andB39), salinities
are generallylower andrangefrom 0 to 34%%
the highest salinitiesoccurring from July
throughSeptember.
TOTAL LENGTH - MM
The averagelengthof youngsolecollected
at
B15 increasedfrom 40.3 mm in April to
FIGURE2.--Length frequencydistributionof juvenile Englishsolecollectedat stationB15 in Yaquina 115.2mm in August.The averagelengththen
Bay.
dropped slightly during the succeeding3
* The four fish collected in March are included
months
as a resultof larger fish'semigrating
here.
from the estuary(Table 1).
A smallnumberof youngfishthat appeared
to
be out of phasewith the dominant size
presentfrom Octoberthrough March. In
class
in the estuarywas found during most
1971,young-of-the-year
fish first appeared
in
Februarybut werenot presentin substantial monthsof the year (Fig. 2). This may be
numbers until April. Catch-per-unit-effortdue to a relatively small number of late
information
indicates
thatemigration
fromthe spawners,accountingfor the very small fish
TABLEL--Average lengthand catch-per-unit-e]/ort
o/ Englishsolecollectedat threestationsin YaquinaBay,
1970-72. (Ranges in parentheses)
B15
Month
December
January
February
March
April
May
JLme
July
August
September
October
November
Average length
(mm)
100.1
104.3
110.8
53.0
40.3
43.7
71.7
86.0
115.2
112.2
110.6
96.2
(80-111
(78-132
(46-133
(34-91)
(22-13•
(21-151
(41-102
(47-111
(55-195
(56-147
(76-132
(75-114
December
35.2 (21-101
January
February
38.2 (23-100
61.4 (22-12•
B29
Catch-perunit-error[
Catch-per-
(mm)
unit-effort
17
98.3 (91-110)
53
--
24
4
25.2
507
499
154
231
208.1
58
12
13.5
79
38.3
B39
Average length
(mm)
16
0
95.0 (78-108)
4
No sample
30.0 (one fish)
0.5
58.5 (38-119)
32
67.3 (37-100)
32
73.9 (48-96)
41
85.3 (64-106)
7.5
102.0 (78-133)
104.2 (76-136)
90.3 (78-105)
35.0 (20-97)
---
Average length Catch-per-
10.5
59.5
11
40
0
0
unit-effort
No sample
--
No sample
No sample
---82 (one fish)
84.2 (69-97)
12
102.9 (77-126)
109.8 (92-123)
12
14
109.5 (108-111)
-No sample
No sample
408
TRANS. AMER. FISH. SOC.,1973,NO. 2
TaBLe,
2.--zlveragelengthand catch.per.
unit-effortof Englishsole collectedin Pacific Oceanadjacentto
YaquinaBaywiththepercentage
of O-group
individuals
in samples,
1970-71.(Ranges
in parentheses)
Percentage of O-group
Averagelength
(ram)
Month
December
191.2 (93-434)
January
239.5(71-382)
February
March
138.4(71-390)
147.5(78-272)
188.6(112-276)
170.1(104-305)
220.5(104-355)
204.6(69-398)
October
November
December
Catch-pernnit-effort
(< 140 ram) English
solein sample
59
54.8
33.9
No sample
26
12.0
30.5
18.4
50.7
43.5
11.8
30.8
53.5
31
177.6 (95-274)
April
May
June
July
August
September
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Number of fish
measured
19.0
11
23
56
26
68
136
195.6 (61-395)
205.5 (76-410)
155.7 (73-348)
6.4
4.6
14.3
44.4
16.2
54.8
19.4
76
198
84
57.1
12.7
9.9
9.8
4.1
10.3
during Novemberand Decembercontainedan
increasedproportion of 0-group sole, 30.8
and 53.5% respectively.This increasewas
probably the result of emigrationof the
O-groupfrom the estuaryduring October.
The presenceof small numbersof the
relative abundance from December 1971
0-groupin the offshoresamples
collected
during the remainingmonthsof the year is best
throughFebruary1972 (Fig. 2).
Although
maturestarryflounder(Platich- explainedby the extendedspawningseason.
thysstellatus)
wereabundant
in bay samples Althoughsurf conditionspreventedregular
and mature sand sole (Psettichthys
melano- samplingat a depthof 10 m on the opencoast,
stictus) were occasionallycollected,adult sampleswere collectedin May when 0-group
Englishsolewerenevercapturedin Yaquina English sole were abundantin the estuary,
Bay.
and in October when emigration from the
Theaverage
lengths
andcatch-per-unit-effort
estuary was occurring. These samplesand
for fish collectedoffshoreare givenin Table samplesfrom previousyearsin the areanever
2. Samples
collected
from Januarythrough includedEnglishsole,juvenileor adult. This
April 1971 contained
few fish. Roughsea areais, however,the habitatfor 0-groupsand
conditions
prevented
samplingin February soleand occasionally
for 0-groupbutter sole
andfewlargefishwerepresentin theMarch
(Isopsettaisolepis
).
collected in late summer and fall and for the
relativelylargefishpresentin the spring.
The time of arrival of the 0-groupin the
estuarymay vary from year to year. This
wasindicatedby the low numbersof 0-group
solein theestuaryuntilApril 1971andtheir
andApril samples.
Englishsolewereabun-
dantin samples
collected
from May through
PARASITES
October
andtheproportion
in the0-group(less
than 140 mm) was quite constant,usually Fifteenspeciesof parasiteswere associated
around 10% (Table 2). Samplesobtained with 0-groupEnglish sole in Yaquina Bay
lageniformisin Englishsolefrom YaquinaBay, 1970-71
TABLE&--Incidence and intensityof Echinorhynchus
B29 and B39 combined
B15
Average
Month
Number
of fish
length
(ram)
Average
Incidence intensity per
(%)
infected fish
December
14
100.1
57.1
7.6
January
February
18
27
104.2
110.7
55.5
51.8
3.4
4.1
ril
y
126
120
9.5
14.2
1.3
1.1
March
June
ly
ugust
September
October
November
4
50
36
32
85
64
24
53.0
39.7
43.8
78.4
93.2
119.2
114.6
113.3
96.3
0
2.0
0
37.5
27.1
7.8
37.5
0
1.0
0
2.5
3.3
5.2
5.0
Number
of fish
6
o
4
0
i
30
25
37
27
40
73
13
Average
lengt}i
(ram)
Average
Incidence intensityper
(%)
infected fish
10.8
98.3
66.6
9•.0
35.0
7•.0
•
54.6
67.3
53.3
56.0
74.1
59.5
2.0
2.6
84.0
102.5
106.1
93.3
40.7
52.5
80.8
69.2
2.1
5.5
4.8
7.1
•.3
•
2.5
OLSON AND PRATT--ENGLISH
SOLE NURSERY
GROUNDS
409
Ta•nE 4.--Incldence o/Echinorhynchuslageniformisin English sole collectedin Paci/ic Ocean adjacent to
Yaquina Bay, 1970-71
Month
Incidence
(%)
Number of O-group
fish examined
Incidence
(%)
30.0
December
59
15.2
20
January
31
3.2
2
26
No sample
15.4
11
18.2
February
March
April
May
June
July
August
September
October
November
December
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Total number of
fish examined
23
56
26
66
99
64
125
75
13.0
1.8
8.8
12.1
9.1
12.5
15.2
24.0
10
8
11
11
8
6
14
9
61
44
0
20.0
25.0
18.2
0
12.5
50.0
14.3
33.3
24.6
34.1
Average length of
O-group fish examined
(mm)
121.4
75.5
126.3
86.6
104.5
182.2
126.0
124.5
109.3
120.3
112.9
121.0
and an additional seven speciesparasitized infectionin 0-groupEnglishsolefrom Yaquina
offshorefish. Of these,threeparasitesappear Bay is presentedin Table 3. For undeterto have life cyclesthat operateonly within mined reasons, the incidence of infection at
from April
the estuary. Thesewere the acanthocephalan,stationB15 fluctuatedconsiderably
Echinorhynchuslageni]ormis,the nematode through July. Incidencepeaked in August
Philometra americana, and a microsporidan and September,droppedin October,and inprotozoan,Glugea sp. The trematode,Zoo- creasedagain in Novemberafter the bulk of
gonusdextrocirrus,and metacercariaof the the O-groupfish had emigratedfrom the bay.
trematode,Otodistomumveliporum, are ap- The incidencesof infectionwith E. lageni]ormis in fish collectedat stationsB29 and
parentlyacquiredonly in offshoreareas.
Available evidence indicates that, on the
B39 were similar and the data from these two
stations were combined in Table 3. The inci-
Oregoncoast,the life cycleof E. lageni]ormis
operatesonly in estuaries.Evidencefor this denceat theseupperstationswassubstantially
includes: (1) the only known intermediate higherthat at stationB15 duringmostmonths,
host (Olson and Pratt, 1971) is Corophium an indicationthat the parasitecycleoperates
spinicorne,
an amphipodcommonin brackish mostefficientlyin the upper estuary.
The incidenceof E. lageni/ormisinfection
water and unreportedoffshore,(2) the only
fishhostsknownin Oregon,the starryflounder offshoreis given in Table 4. As previously
(Platitchthysstellatus)and the Englishsole, mentioned, fish of 140 mm or less in total
spend considerableperiods of time in the length were consideredto be 0-group indiestuary,and (3) flatfish that do not frequent viduals that had potentiallyemigratedfrom
the estuaryare uninfected.Theselatter in- the bay. Fish in this size groupwere present
cludeO-groupsand and butter solecollected in greatestnumbersduring November and
in depthsof 10 to 40 m offshorewhichwould December,immediatelyafter the Octoberemibe verylikelyto feedon the intermediate
host gration from the bay.
Sincethe bulk of the Englishsole using
of E. lageni]ormisif it were present.
It was concludedthat the E. lageni]ormis Yaquina Bay as a nurseryare found in the
foundin Englishsolecollectedoffshorewere lower estuary (B15), the incidence of E.
acquiredby the fish in an estuaryand that lageni/ormisobservedat the lowerstationwas
this parasitecouldbe usedas an indicatorof consideredto be most typical of the entire
former estuarine residence.
bay population. The incidencesof infection
The life spanof E. lageni]ormisin the fish observedduring Augustand Septemberwere
hostis probablynot over I year (Olsonand combinedto producewhat was consideredto
Pratt, 1971), so that its usefulnessas a tag be the averageincidenceof infectionattained
diminisheswithin a relativelyshorttime after by 0-groupEnglishsolewhile on the Yaquina
the fish leave the source of infection.
Bay nurseryground. This wasthen compared
Incidenceand intensityof E. lageni/ormis with the incidence observed in fish less than
410
TRANS. AMER. FISH. SOC., 1973, NO. 2
TABLE5.--Incidenceoj Philometraamericanaand Glugeasp. in Englishsolejrom YaquinaBay, 1970-71
B15
Number
of fish a•,ericaua
examined
(%)
Month
April-August
September
October
364
85
64
November
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Incidence
of P.
24
0
0
0
8.3
B29
Incidence
of Glugea
(%)
0
1.2
3.1
25.0
Number
Incidence
of P.
B39
Incidence
of fish americana of Glugea
examined (%)
(%)
109
17
60
11
0
0
11.6
0
0.9
17.6
35.0
36.3
Nmnber
Incidence
of P.
Incidence
of fish americana of Glttgea
examined (%)
(%)
13
23
13
0
0
0
2
0
0
30.4
69.2
100.0
140 mm long collectedoffshoreduring NoThe adulttrematodeZoogonusdextrocirrus
vemberand December,after emigrationfrom and metacercariaof Otodistomum
veliporum
the bay. Of the 117 sole examh•edfrom the are common parasitesof offshore English
August-September
bay collection,35 or 29.9% sole,but not of thosefrom YaquinaBay, an
were infected; of the 105 offshore fish ex- indicationthat fish becomeinfectedonly in
amined from the November-December
collecoffshorewaters. Althoughthe life span of
tions, 30 or 28.5% were infected with E.
lagenijormis.These data suggestthat there
wasno sizableinflux of 0-groupEnglishsole
from otherthan estuarinenurserygroundsto
the offshorestudyarea.
The
nematode
Philometra
americana
and
Z. dextrocirrus
may be relativelyshort,O.
veliporummetacercariae
probabylive for a
number of years. Of the 856 sole examined
from the bay, none was infectedwith O.
veliporumandonlytwohadoneZ. dextrocirrus
each. This indicatesa negligibleamountof
back-and-forth
movement
between
theestuary
andthe offshoreareas.WhenO-groupEnglish
soleleavethe estuarine
nurseryground,they
leavepermanently.
microsporidanGlugea sp. appear to infect
Englishsoleonly in the estuary. In Oregon,
P. americanahas been reported by Olson
(1972) andGlugeasp.a protozoanthat forms
Other parasitesfound did not show charcystsin the intestinalwall, was reportedin
YaquhlaBay by Wellings,Ashleyand McArn acteristicsof infectionor life cycle that al(1969). The life spansof theseparasitesare lowedtheir useas naturaltags. The appearnot known,but almostcertainlyare over 1 anceof 0-groupEnglishsolein YaquinaBay
"no capriyear. The localitywhereinfectionof fish with is as Westrheim(1955) suggested
both of theseparasitesoccursappearsto be ciousevent." Rather,the estuaryis a natural
restrictedto the upperestuarywherethe inci- andimportantnurserygroundfor this species.
denceof infectionreachesa peak during the It is also apparentthat the shallow,sandy
fall (Table 5). Althoughthe presence
of these bottomareasof the opencoastarenot suitable
parasitesin offshoreEnglish sole doesindi- for 0-groupEnglishsolealthoughtheseareas
cate former estuarineresidence,the incidence do generallyfit Ketchen's(1956) description
of infectionin the bay populations
as a whole of thenurserygroundsin HecateStrait,British
does not reach levels high enough to be of Columbia. The primary differencebetween
use in determiningthe degree of estuarine thetwo areasis probablythe turbulentwaters
utilizationby thesefish. It can be concluded of the exposedOregoncoast,so an additional
that offshoreEnglishsolecarryingthesepara- characteristic
of Englishsolenurserygrounds
sites had at some time occupiedthe upper may be that of relativelyquietwater. On the
estuary. Of the 105 0-groupsolecaughtoff- Oregoncoasttheseareasare found only in
shoreduring November-December,
eight were baysand estuaries
and,althoughall werenot
infectedwith Glugea sp. and one with P. sampled,it is likely that all are important
americana. This amounts to 8.6% of the sam- Englishsolenurserygrounds.Bothtrawl and
ple whichprobablygivesa conservative
indi- parasiteinformationgive strongevidencethat
cationof the proportionthat utilizethe upper estuaries
maybetheexclusive
nurserygrounds
estuary as a nursery.
for Englishsoleon the Oregoncoast.
OLSON AND
PRATT---ENGLISH
We wouldlike to thankEugeneM. Burreson
who assisted in the col-
lection and examinationof specimens,Dr.
James E. McCauley who critically read the
manuscript,and membersof the OregonFish
Commission,especially Robert L. Demory,
who gave valuableadvice. The researchwas
supportedin part by National Oceanic and
AtmosphericAdministration (maintained by
the U.S. Dept. of Commerce)Institutional
Downloaded by [Oregon State University] at 13:09 17 October 2011
Sea Grant
411
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