OYSTER 14)RTALITY
NlRTALI'IY S'ruDY
OYSTER
STUDY
ANNUAL REPORT July 1,
1, 1970-June
1970-June 30,
30, 1971
1971 Gary G.
on
G. Gibs
Gibson
Coimnerce U.S.
U.S. Department of Comerce
Service Fish
and Wildlife Service
Fish and
National Harine
Service Marine Fisheries Service
14-17-0001-2357 Contract No.
Contract
No. 14-17-0001-2357
1971
September 1971
OYSTER !ORTALIIY
MORTALITY STUDY
STJDY
OYSTER
ABSTRACT
Oyster mortality data collected from suspended trays
trays at three
three sub­
subtidal locations
locations in Yaquina Bay disclosed an unusually high
high 26.5%
26.5% Pacific
oyster (Crcmaoatrea
(C~s08trea gigaa)
gigas) mortality
mortality during
during the
the study
study year.
year. Almost
Almost all
all
of this
resulted from
from culling
culling damage
damage which
which occurred
occurred previous
previous
this mortality resulted
to introduction of the oysters into
into trays.
trays. Native
Native oyster
oyster mortality
mortality was
was
22.n, 1.3%
1.5% higher than the average mortality
mortality of
of the
the previous
previous 44 years.
years.
22.1%,
Mortality of
of bay
bay naissels
mussels was 44.2%.
44.2%. No evident
evident causes
causes for
for this
this high
Mortality
mortality were noted.
noted. Mussels were
were not
not monitored
monitored in
in previous
previous years.
years.
Pacific oyster mortality in
in intertidal trays
trays was
was 7.3%
7.3% at
at the
the
Tillamook Bay
Bay station;
station; 6.7%
6.7% at
at the
the Coos
Coos Bay
Bay station.
station.
Tillamook
A total
total of
of approximately
approximately 1,750
1,750 oysters
oysters and mussels were collected
collected
A
the National I·iarine
Fisheries Service
during the study year and sent to the
Marine Fisheries
(NMFS)
examination.
(NMFS) Oxford
Oxford Laboratory for histological examination.
INTRODUCTION
INTRODUCTION
Objectives of
of Oregon's
oyster mortality study
study for
for the
the past year,
Oregonts oyster
year,
1971, were similar
similar to
to those
those of
of previous
previous years:
years:
ending in March 1971,
(1)
Till8Dlook, and
(1) To monitor oyster mortality in Yaquina, Tillamook,
Coos bays.
(2)
furnish oysters to
to the
the NMFS
NMFS laboratory
laboratory in
in Oxford, (2) To furnish
Maryland, for
for histological
histological examination.
examination. MATERIALS AND ME1HODS
METhODS
Mortality Stations
Mortality data were collected at three subtidal stations in Yaquina
Bay (Figure
(Figure 1) and
and at single intertidal locations
locations in Tillamook and Coos
Bay
Coos
bays.
bays.
Suspended trays at each Yaquina Bay station initially contained 130
150
Pacific oysters
oysters (Crao8oetrea
(Crass08trea
gigas),
igaa), 300
300 native
native oysters
oysters (Ostrea
(Ostrea lUPida»)
lurda),
and 150 bay mussels (Mytilw,
(Mytilus edulis),
edulis).
for mortalities.
These stations
stations were checked
checked monthly
All stations
suspended
All
stations suspended
from
floating docks
docks at
at
from floating
aa depth
depth of·
of
Yaquina Bay
Yaquin8.
Bay
Station
A -- 44 ft.
ft.
Station A
Station
ft.
Station BB -- 66 ft.
Station
C -- 88 ft.
ft.
Station C
Pacific
Pacific
Ocean
Ocean
o
1
Mile
Figure 1,
Figure
1.
Locations
of the
the Oyster
Oyster i4ortality
Mortality Stations
BK,Y
Locations of
Stations in
in Yaquina
Yaquina Bay
N
3.
Tillamook
stations
contained 150
150 Pacific
Tillamookand
andCoos
CoosBay
Bay
stationseach
eachinitially
initially contained
Pacific
oysters. These
These trayed
oysters, along
along with
withthose
thoseon
onthe
thesurrounding
surroundingcomcom­
trayed oysters,
mercial
merci
al beds,
were checked
checked every
ds, were
every 33 months
monthsfor
formortalities.
mortalities.
Histological
Samples
Histological Samples
Pacific
oystersand
andbay
baynvssels
musselsfrom
fromYaquina,
Yaquina,Tillamook,
Tillamook,and
andCoos
Coos
Pacific oysters
bays
native oysters
oystersfrom
fromYaquina
YaquinaBay
Bay were
were sent
senttoto
NMFS Oxford
Oxford
bays and native
thethe
NMFS
Laboratory
examination.
Laboratory for
for histological
histological examination.
RESULTS AND
AND DISCUSSION
DISCUSSION
RESULTS
Mortality
Mortality Stations
Pacific oyster
oyster mortality
mortality(1-year-old
(l-year-oldanimals)
animals)was
was26%
26% at
at the
theYaquina
Yaquina
Bay stations
during the
year (Table
(Table 1)
1). This
Wlusually high
Bay
stations during
the past year
This unusually
high mortality
*
from culling
culling damage
damage which
resulted from
whichoccurred
occurredprior
priorto
to introduction
introduction into
the trays.
the
Less
1% was
Less than 1%
was from
fromother
other causes.
Shell breakage
breakage was
was evi­
evi-
dent in
allof
ofthe
thedead
deadanimals;
animals; shell
shellrepair
repairwas
was noticed
noticedin
inmany
many of
dent
in all
of the
remaining live
died were
were not
not
remaining
live oysters. The
The oysters
oysters that
that died
able to build
buildnew
new
shell across
across broken
broken areas fast
fastenough
enough to
to prevent
prevent the
the invasion
invasion of
ofmarine
marine
organisms
organismsinto
into the
the mantle
mantle cavities.
cavities.
oyster mortalities
mortalitiesreported
reportedfor
for
previousyears
yearswere
were8.6%
8.6%
Pacific oyster
previous
during
1969-70, 1.1%
1.1\ during
1968-69, 1.5%
1.5% for
1967-68, and
and 1.8%
1.8\ during
during 1969-70,
during 1968-69,
for 1967-68,
during
1966-67.
Native
oyster mortality
mortalityininYaquina
YaquinaBay
Bay (various
(variousages)
ages)was
was22.1%
22.1%
Native oyster
during
study year
(Table 2).
during the
the study
year (Table
About
mortality
Aboutone-third
one-thirdof
of this
this mortality
occurred
the uppermost
uppermost bay
(A) following
following aa long period of
occurred at
at the
baystation
station (A)
low
during the
the winter.
winter.
lowsalinities
salinities during
l\lortalities during
during previous
previous years
years
Mortalities
were 26.5%
26.5% for
1969-70, 28.2%
28.2% during
1968-69, 9,6%
9.6% during 1967-68,
1967-68, and
and
were
for 1969-70,
during 1968-69,
18.2% for
for 1966-67.
18.2%
1966-67.
4.
4.
Table
Table 1.
1. Pacific Oyster Mortality in Yaquina Bay by Station and
Period, April 1970-March 1971
Quarterly Period,
Number Dead Oysters
Qlsters
Station
C
B
B
C
Total
Percentage
Mortality
by
bl Quarter
guarter
Date
A
A
1970
April--:AP'rilJune
28
99
33
33
70
15.6
10
10
22
33
45
11.8
OctoberDecember
11
0
0
0
11
0.3
1971
1971 .
--:JanuaryJanuaryMarch
11
0
0
0
11
0.3
40
11
11
66
86
117
JulySeptember
Total
------------------------------------Total Total Percentage
Hortali ty
Annual iortality
Table 2.
2.
26.0
Native Oyster Mortality in Yaquina Bay by Station and
Quarterly Period,
Period, April 1970-March 1971
Total
Total
Percentage
Mortality
by Quarter
bl
guarter
15
41
41
4.6
12
12
26
65
7.6
7.6
14
12
46
46
5,8
5.8
Number Dead
Number
Dead Oysters
0lsters
Station
B
B
C
C
Date
A
1970
April-xprilJtme
June
20
6
JulySeptember
27
OctoberDecember
20
20
1971
--:JanuaryJanuaxyMarch
39
39
8
8
106
106
40
8.6
8.6
47
Y
-------------------------------------
Total Total Percentage Annual Mortality / T'cj iost Januanj 15
53
199
22.1
221
1971.
S.
5.
Bay DIlSsel
(l-year-old animals)
animals) in suspended trays
mussel mortality (1-year-old
trays was
was 44.2\
44.2%
during the past year in Yaquina
Yaquina Bay
Bay (Table
(Table 3).
3).
There was no apparent reason
for this
this mortality;
mortality; and it cannot
cannot be
be said to be high
high or low since mussel
mussel
mortality was
was not
not monitored
monitored in
in previous
previous years.
years.
mortality
Table 3.
3. Bay Mussel Mortality in Yaquina Bay by Station and Quarterly Period,
Period~ April 1970-March 1971 Date
pate
A
A
1970
April-April
June
Number Dead
Dead Mussels
Number
Station
C
C
B
B
Total
Total
Percentage
Mortality
byQuarter
bI Quarter
22
11
11
4
4
0.9
JulySeptember
27
31
51
109
24.4
OctoberOctthe rDecember
IS
15
27
29
71
71
21.1
211
1971
--:JanuaryJanuazyMarch
14
11
Y
15
15
7.6
------------------------------------Total 58
60
81
199
Total Percentage
Annual Mortality
ii
Y
44.2
Tray
Tz-ay lost
Zest Jøuary
JantltU?/ 15,
16" 1971.
19'11.
At the Tillamook
Tillaxnook Bay
Bay station,
station, 7.3%
7.3% of
of the
the tray
tray held
held animals
animals died
died
(Table 4).
4).
compares to
to 2.1%
2.1% during
during 1969-70
1969-70 and
and 4.6%
4.6% for
for 1968-69.
1968-69.
This compares
In Coos Bay 6.7\
of the
the experimental
experimental oysters
oysters died
died (Table
(Table 4).
4).
In
6.7% of
MorMor­
tality during the
the 2 previous
previous years
years was
was 6.9% in
in 1969-70 and 27.1\
27.1% for
114J
1968-69.
6.
Table 4.
4. Pacific Oyster
Oyster Mortality
Mortality in
in Tillainook
Tillamook and
Table
and Coos
Coos Bays
by Quarterly Period,
Period, April 1970-March 1971
Station
Tillamook Bay
Total
Percentage
Mortality
No. Dead
No.
by Quarter
Date
1970
April -XPril­
Jtme
June
Coos Bay
No.
No. Dead
Total
Percentage
Mortality
Cl!!arter
by Quarter
1
1
0.7
11
0.7
September
Septether
7
7
4.7
4.1
5
5
3.4
3.4
October­
OctoberDecember
Decether
0
o
o0
2
2
1,4
1.4
1971
January---:J'ailuary
­
March
3
3
2.1
2.1
2
2
1.4
July­
July-
- - - - - - - ....... ----------------------------­
Total
10
10
11
11 Total Percentage
Annual Mortality
7.3
7.3
6.7
Samples
Histological Samples
Monthly samples of shellfish sent to the Oxford Laboratory totaled
900 native oysters, 150
150 Pacific
Pacific oysters,
oysters, and
and 700
700 bay
bay mussels.
mussels.
Histological
findings will be published
published by
by NMFS pathologists
pathologists in
in aa separate
separate report.
report.
findings