RESOURCE SURVEYS ON THE
CONTINENTAL SHELF OFF OREGON
ANNUAL REPORT
J u l y 1, 1973 t o June 30, 1974
Robert L. Demory
Fish Commission o f Oregon
National Cbrine Fisheries Service
i j a t i onal Oceanic and Atmospheric Administration
U.S. Department o f Commerce
Comnercial Fisheries Research and Development Act
Project No. 1-78-D-3
Contract No. 04-4-208-6
June 1974
RESOURCE SURVEY ON THE CONTINENTAL SHELF OFF OREGON
Introduction
This r e p o r t summarizes program progress i n FY 1974. A c t i v i t i e s were
d i r e c t e d e n t i r e l y a t completing t h e t h i r d o f f o u r phases o f work s t a r t e d i n
1971. The survey conducted i n September 1973 was t h e second r u n over the
c o n t i n e n t a l s h e l f o f f t h e northern Oregon coast.
Objectives o f the survey were t o o b t a i n estimates o f biomass o f f i s h e s
occupying t h e c o n t i n e n t a l s h e l f w i t h p a r t i c u l a r emphasis on f l a t fishes. We
a r e a l s o indexing year-class s t r e n g t h o f f l a t f i s h e s important t o the commercial
f i s h e r y p r i o r t o t h e i r recruitment t o t h e f i s h e r y .
Methods
F i s h i n g Methods
I n 1973 l e n g t h o f tow was increased t o 1.0 n a u t i c a l mile, one-quarter
m i l e g r e a t e r than i n 1971 and 1972.
The t r a w l used i n 1971-72 was modified by t h e a d d i t i o n o f a chain-rubberd i s c footrope f o r t h e 1973 survey. Trawl measurements showed a h o r i z o n t a l
opening o f 30 f e e t and a v e r t i c a l opening o f 5+ f e e t . This contrasts t o 32
f e e t and 4.5 f e e t f o r t h e t r a w l as used i n 1971-72.
S t a t i o n p a t t e r n i n 1973 was i d e n t i c a l t o t h a t o f 1971 on t h e c o n t i n e n t a l
s h e l f , b u t new stations, o u t t o 250 fathoms, were added i n 1973 (Figure 1).
Catch Processing
Techniques developed d u r i n g t h e 1971 survey f o r handling t h e catch were
f o l lowed i n 1973 (Demory and Robinson, 1972). Sampling o f t h e catch was
modified from previous surveys i n t h a t t h e p r o p o r t i o n o f t h e catch t o be
sampled was f i x e d f o r each species p r i o r t o t h e cruise. Sample r a t e , o r t h e
p r o p o r t i o n o f t h e catch sampled was as f o l l o w s :
Speci es
Proportion, sample: catch
Slender sole, b u t t e r s o l e
sand sole, f l a t h e a d s o l e
P e t r a l e sole, arrowtooth f l o u n d e r
1:2
Dover s o l e
1:4
English sole, r e x sole, P a c i f i c sanddab
1:4 o r 1:5
These sample r a t e s were adhered t o i n n e a r l y a l l cases, b u t lower r a t e s o f 1:10
and 1:20 were used when very l a r g e catches were made, especial l y i n t h e case of
English sole. The sample r a t e f o r P a c i f i c sanddab was decreased from 1:4 t o 1:5
about midway through t h e cruise.
Estimates o f Biomass
Biomass was determined as d e t a i l e d i n t h e annual r e p o r t f o r FY 1972 (op.
c i t. ). A1 though biomass was c a l c u l a t e d f o r a1 1 tows, r e s u l t s were 1i m i t e d t o
t h e f i r s t 19 t r a c k l i n e s so t h a t r e s u l t s could be cornpared t o estimates obtained
i n 1971.
Year-Class Strength
Index t o year-class s t r e n g t h was c a l c u l a t e d i n percent frequency.
Kesul t s and Discussion
Fishing
Because o f t h e complete demolition of one t r a w l and severe damage t o the
standby t r a w l , t h e deep water s t a t i o n s were abandoned. I t i s planned t o t r a w l
these s t a t i o n s i n 1974 a f t e r t h e remainder of t h e c o n t i n e n t a l s h e l f s t a t i o n s
have been occupied. A r o l l e r type f o o t rope w i l l be added t o t h e t r a w l .
Estimates o f Biomass
The biomass estimate between t h e Columbia R i v e r and Yaquina Head was n e a r l y
233 m i l l i o n pounds (Table 1). O f t h i s n e a r l y 37% was o u t s i d e t h e 12-mile contiguous zone. The r o c k f i s h complex amounted t o 20.3 m i l l i o n pounds o f which
73% was o u t s i d e 12 miles. Estimates o f biomass o f r o c k f i s h a r e u n r e a l i s t i c
because t h e t r a w l i s n o t e f f i c i e n t a t catching r o c k f i s h o r other p e l a g i c o r
semi-pelagic f i s h .
'The f l a t f i s h complex amounted t o n e a r l y 78 m i l 1i o n pounds, o f which 47%
was o u t s i d e 12 miles. Dover s o l e was most abundant a t 27.7 m i l l i o n pounds
followed by arrowtooth flounder and r e x s o l e a t 13.9 and 11.3 m i l l i o n pounds,
respectively.
Because t h e 1973 survey covered t h e same area as t h e 1971 survey, estimates
of biomass can be compared. The percent change from 1971 ranged from -63% f o r
hake t o over 1000% f o r rock s o l e (Table 1). This range i s extreme f o r two reasons:
hake a r e a semi-pelagic species; and rock s o l e a r e seldom caught. Overall t h e
1973 estimate i s 39% l e s s than 1971. Excluding hake the change i s 10% r110t-ei n
1973. Estimates o f skates were n e a r l y equal, b u t d o g f i s h was 581% g r e a t e r i n 1973.
The f l a t f i s h complex changed by o n l y -3% even though rock s o l e accounted f o r
t h e g r e a t e s t change o f any species. For those species of f l a t f i s h t h a t a r e frequently caught, P a c i f i c sanddab showed t h e g r e a t e s t change a t +46% followed by
p e t r a l e s o l e a t -36% and English s o l e a t -34%. Dover sole, r e x sole, and arrowt o o t h flounder showed t h e l e a s t change a t +3, -8, and +16%, respectively.
Year-Cl ass Strength
A r e l a t i v e measure o f year-class s t r e n g t h i s i n d i c a t e d by f o l l o w i n g a yearclass between t h e 1971 and 1973 surveys. A strong 1966 year class i s common f o r
f o u r o f t h e s i x species shown i n F i g u r e 2. Only f o r P a c i f i c sanddab i s t h e 1966
Table 1.
Estimates of Biomass i n t h e North Half o f the Survey Area, Columbia
River t o Yaquina Head, i n 1971 and 1973. Numbers i n Parentheses
a r e t h e Breakdown o f the F l a t f i s h Category.
~housandsof Pounds
Species
1971
1973
% Change
from 1971
% Outside
12 m i l e s
1971 1973
Spiny dogfish
Skate
Hatfish
P a c i f i c cod
P a c i f i c hake
Rockfish
Sablefish
Lingcod
Flatfish
P a c i f i c sanddab
Arrowtooth f 1ounder
S 1ender s o l e
Petrale sole
Flathead s o l e
Sand s o l e
Butter sole
English s o l e
Rock s o l e
Dover s o l e
Rex s o l e
S t a r r y f 1ounder
C u r l f i n sole
(390)
(298)
(14,397)
(29)
(26,773)
(12,313)
( 148)
(154)
14,080
19,225
12,577
1,656
67,890
20,335
15,141
3,915
77,799
(7,920)
(13,928)
(679)
(4,737)
(599)
(297)
( 600
(9,473)
(405)
(27,680)
(11,292)
( 129)
(60)
Total A l l Species
330,772
232,618
-
30
44
37
Total Less Hake
149,315
164,728
+ 10
--
.--
2,069
19,357
10,845
1,482
181,457
20,609
9,259
5,238
80,456
(5,420)
(11,993)
(523)
(7,357)
(GQ1)
+581
- 1
+ 16
+ 12
- 63
- 1
+ 64
- 25
- 3
+(46)
+( 16)
+(30)
436)
- (9)
424)
+( 101)434)
+(1,297)
+ (3)
- (8)
-( 13)
-(61)
26
46
18
47
26
23
19
12
42
12
64
73
60
72
38
39
46
47
(5) (3)
(70) (67)
(71) (71)
(17) (24)
(82) (87)
(0) (0)
(4 (0)
(4) (1)
(8) (11)
(72) (74)
(38) (40)
(0) (0)
(1) (7)
04
O h
i-m
0
CY
34
-
-
- p a .1
7
V)
LC,
rc
U -r
a m
aJ>- LL.
year class dominant i n 1971 and 1973. The 1968 year class i s a1 so reasonably
strong in English and petrale sole and dominant for arrowtooth flounder. The
1961 year class s t i l l shows in Dover, English, petrale, and rex sole. This
particular year class was the strongest on record f o r English sole and was
dominant i n tile fishery over a three year period, 1966-68. I t was the
strongest year class f o r Dover sole since the 1942 year class.
Literature Cited
Demory, R.L. and 3.6. Robinson. 1972. Resource surveys on the continental
shelf off Oregon. Conim. Fish. Res. and Dev. Act Annual Report, July 1, 1971
t o June 30, 1972. Fish Comm. of Ore. Proc. Rept., 13 p.