Stock assessment of small yellow croaker considering … · Stock assessment of small yellow...
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Stock assessment of small yellow croaker Stock assessment of small yellow croaker
considering the impact of yellow goosefish considering the impact of yellow goosefish
predation in the East China Sea predation in the East China Sea
Young Il Seo, Joo Il Kim, Taeg Yun Oh, Sun Kil Lee,
Chang Ik Zhang, Jae Bong Lee, and Jung Hwa Choi
Anchovy
Pinkgray goby
Chefoo thryssa
Black throat sea perch
Spearnose grenadier
Yellow croaker
Hair tail
croaker
White croaker
Common hairfin anchovy
Vertical striped cardinalfish
Belenger’s jewfish
Bluefin sea robin
Yellow goosefish
Horse mackerel
Chub mackerel
Tanaka’s snailfish
Agassiz’s snailfish
Lizardfish
Butterfish
Other food
Prey of Yellow goosefishPrey of Yellow goosefish
From yellow goosefish stomach, 69 fish species were found.
Yellow goosefishYellow goosefish
Lophius litulon
Valuable groundfish
Max. size: 150 cm
High TL species in food web
as a predator with a BIG
MOUTH
Mainly feeds on small yellow
croaker (more than 45% of
its total diet composition)
Small Yellow croakerSmall Yellow croaker
Larimichthys polyactis
one of the most valuable fish
species and ecologically
important species in Korean
marine ecosystem
This fish stock has been
decreasing due to overfishing
and ecosystem impacts, such as
predation mortality
100 kg/㎢
100~1K
1K~2K
2K <
Distributions of Yellow goosefish (Spring)Distributions of Yellow goosefish (Spring)
100 kg/㎢
100~1K
1K~2K
2,000<
Distributions of Yellow goosefish (Summer)Distributions of Yellow goosefish (Summer)
100 kg/㎢
100~1K
1K~2K
2K <
Distributions of Yellow goosefish (Autumn)Distributions of Yellow goosefish (Autumn)
100 kg/㎢
100~1K
1K~2K
2K <
Distributions of Yellow goosefish (Winter)Distributions of Yellow goosefish (Winter) Small yellow croaker (Spring)Small yellow croaker (Spring)
< 10 MT
10 ~ 50
50 ~ 100
100~ 250
Small yellow croaker (Summer)Small yellow croaker (Summer)
< 10 MT
10 ~ 50
50 ~ 100
100~ 250
Small yellow croaker (Autumn)Small yellow croaker (Autumn)
< 10 MT
10 ~ 50
50 ~ 100
100~ 250
Small yellow croaker (Winter)Small yellow croaker (Winter)
< 10 MT
10 ~ 50
50 ~ 100
100~ 250
Stomach contents of Yellow goosefishStomach contents of Yellow goosefish
Dominant species of stomach contents are hakodate sand shrimp, anchovy and small size fishes in the coastal area.
Number
13%
9%
8%
7%
40%
3%3%3%4%
4%
6%haKodate sand shrimpanchovyunidentif ied f isheschinese ditch praw npinkgray gobychefoo thryssablack throat sea perchspearnose grenadierunidentif ied shrimpsmantis shrimpothers
Weight
7%
6%
6%
6%
5%
53%
3%3% 3%4%
4% bluefin sea robinunidentif ied f ishesblack throat sea perchyellow goosefishanchovyspearnose grenadierPleuronectidae sp.pinkgray gobyhorse mackerel/w hite croakerothers
South Coast (2004-2006)
Stomach contents of Yellow goosefishStomach contents of Yellow goosefish
Dominant species of stomach contents are anchovy and small yellow croaker in the EEZ of Korea.
Number2%
5%45%
20% 5%
14%
3%2%2%
1%
28%
1% unidentified fishesanchovyyellow croakerLiparidae sp.Crangonidae sp.unidentified shrimpshaKodate sand shrimparrow wormBelenger' s jewfishchinese ditch prawnothers
Weight9% 8%
6%
51%
11%25%
7%2%
2%
2%1%
1%
unidentified fishesyellow croakeranchovyLiparidae sp.Tanaka' s snaifishbutterfishlizardfishBelenger' s jewfishagassiz' snailfishchub mackerel others
EEZ (2004-2005)
Stomach contents of Yellow goosefishStomach contents of Yellow goosefish
Dominant species of stomach contents are small yellow croaker, anchovy and hairtail in the East China Sea.Measured age of prey
Number
5%
4%
5%
2%4%
19%
35%
10%4%
11%
34% 2%
yellow croakeranchovyhair tailCrustaceanscroakerwhite croakercommon hairfin anchovyCephalopodsunidentifiedvertical striped cardinalfishsouthern rough shrimp
Weight
4%
8% 3% 5%
5%
2%
22%
45%35%
3% 3%
yellow croakeranchovyhair tailCrustaceanscroakerwhite croakercommon hairfin anchovyCephalopodsunidentifiedmetallic lantern fish
ECS (1994-1997)
Fishery dataFishery data
Annual variations of catch of small yellow croaker showed a negative correlationship with that of yellow goosefish in Korean waters.
0
10,000
20,000
30,000
40,000
50,000
60,000
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year
Cat
ch o
f SYC
(MT)
0
2000
4000
6000
8000
10000
12000
14000
Cat
ch o
f YG
F (M
T)
Small yellow croakerYellow goosefish
y = -0.0959x + 8893.6R2 = 0.1283, P<0.05
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
0 10,000 20,000 30,000 40,000 50,000 60,000
Yellow croaker (mt)
Yello
w g
oose
fish
(mt)
Multispecies Virtual Population Analysis Multispecies Virtual Population Analysis
Common input data included catch-at-age data (only landings), maturity-at-age, and weight-at-age
Input data of the MSVPA included stomach content data, prey (small yellow croaker, anchovy, hairtail) weight-at-age in the predator stomach contents, predator (yellow goosefish) annual ration, and natural mortality.
Stomach content data and estimates of weight-at-age in the stomach contents of predators from 1994 and 1997 were used because those years had most complete for MSVPA
Predation equationsPredation equations
S - suitability coefficient of prey p for predator iBS - suitable prey biomassR - annual ration of the predator iW - weight at age of prey pM2 - predation mortalityM – natural mortality, M1 – residual mortality, U - stomach content
- avg. predator population, - avg. prey population
∑∑=i a ji
jijiapjiap BS
NRSM
,
,,,,,,2
∑∑+=p a
apapapjiofjiji NWSSBS ,,,,,,,,
( )( )∑∑
=
p ajiapapjiap
jiapapjiapjiap WNU
WNUS
,,,,,,,
,,,,,,,,,, /
/
M2M1M +=
To estimate the stock size from catch at age data and stomach contents of predators, predation mortalities must be known
To calculate predation mortality, the stock size and the suitabilities must be known
Average suitability Average suitability
0 1 2 3 4 5 6
1
2
3
4
5
6
0
0.2
0 1 2 3 4 5 6
1
2
3
4
5
6
0
1
Age
of g
oose
fish
Age
of g
oose
fish
Age of small yellow croaker Age of hair tail
Larger yellow goosefish feed on older prey species.
Comparison of natural mortality Comparison of natural mortality
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 1 2 3 4 5 6 7 8 9 10
Age
Nat
ural
Mor
talit
y MSVPAsingle species
Small yellow croaker
0.0
0.4
0.8
1.2
1.6
2.0
0 1 2 3 4 5 6 7 8 9 10 11 12Age
Nat
ural
Mor
talit
y
MSVPAsingle species
Hairtail
Predatory natural mortality of small yellow croaker was highest at age 3
and that of hairtail was at age 4-5.
Comparison of average abundance Comparison of average abundance
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
1800000
2000000
0 1 2 3 4 5 6
Age
Ave
rage
Pop
ulat
ion
Size
at A
ge
SSVPAMSVPA
Small yellow croaker
0
400000
800000
1200000
1600000
2000000
0 1 2 3 4 5 6Age
Ave
rage
Pop
ulat
ion
Size
at A
ge
SSVPAMSVPA
Hairtail
Average abundance estimates of prey species by MSVPA were higher than those by SSVPA.
The difference of small yellow croaker was high until age 2.
Temporal trend of prey stock sizeTemporal trend of prey stock size
0
2000000
4000000
6000000
8000000
10000000
1988 1991 1994 1997Year
Tota
l Pop
ulat
ion
Estim
ates
SSVPAMSVPA
Small yellow croaker
0
1000000
2000000
3000000
4000000
1988 1991 1994 1997Year
Tota
l Pop
ulat
ion
Estim
ates
SSVPAMSVPA
Hairtail
Total population estimates of prey species by MSVPA were higher than by SSVPA.
Temporal trends of predation mortalityTemporal trends of predation mortality
0.0
0.4
0.8
1.2
1.6
1988 1991 1994 1997Year
Pred
atio
n M
orta
lity
SYC age-3Avg. SYC age-3HTL age-4Avg. HTL age-4
Predation mortalities of prey species at age 3 showed a similar variation
pattern from 1988-1997.
Small yellow croaker consumed by Yellow goosefishSmall yellow croaker consumed by Yellow goosefish
0
500000
1000000
1500000
2000000
2500000
3000000
3500000
4000000
4500000
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997
Year
Num
ber o
f con
sum
ed(th
ousa
nd) Age-6
Age-5Age-4Age-3Age-2Age-1Age-0
0
200000
400000
600000
800000
1000000
1200000
0 1 2 3 4 5 6
Prey age
Sm
all y
ello
w c
roak
erco
nsum
ed(th
ousa
nds)
Age-0 small yellow croaker was the highest consumed by yellow goosefish.
Over 80% of small yellow croaker at ages 0-2 were predated by yellow goosefish.
Reference point of small yellow croaker considering yellow goosefish predation
Reference point of small yellow croaker considering yellow goosefish predation
0
5
10
15
20
25
30
35
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Fishing mortality
YPR
of S
YC, g
0
20
40
60
80
100
120
SPR
ratio
of S
YC, %
SSVPAYGF FcurYGF F30YGF F40SSVPAYGF FcurYGF F30YGF F40
Fcur= 1.11F40%= 0. 28~0.35
ConclusionsConclusions
Adult population sizes are comparable in single species and multispecies models.
Most predation mortality of SYC occurs in age 0 to 2.
Predation impact by yellow goosefish on small yellow croaker was considerable.
Two species management application can be applicable, although the fishing pressures to both species (SYC, YG) need to be reduced in the ECS.