GIANNOULAKI M., SOMARAKIS S., MACHIAS A., SIAPATIS A., PAPACONSTANTINOU C. Hellenic Centre for...

GIANNOULAKI M., SOMARAKIS S., MACHIAS A., SIAPATIS A., PAPACONSTANTINOU C.

Hellenic Centre for Marine Research, PO Box 2214, Iraklion 71003, GreeceDepartment of Biology, University of Crete, PO Box 2208, 41409 Voutes,

Iraklion, Greece

GFCM – Izmir 2008GFCM – Izmir 2008

Stock assessment of the Aegean Sea (GSA 22) Anchovy and Sardine stock by Integrated Catch at

age analysis (ICA)

An Integrated Catch-at-Age analysisAn Integrated Catch-at-Age analysis

was applied based on commercial catch data (2000-2006) was applied based on commercial catch data (2000-2006)

andand tuning indices: the biomass estimates from acoustic surveys and tuning indices: the biomass estimates from acoustic surveys and

Daily Egg Production Method (DEPM) estimates (2003-2006) Daily Egg Production Method (DEPM) estimates (2003-2006)

method that standard VPA assessments are tuned with method that standard VPA assessments are tuned with results from fishery independent stock assessment results from fishery independent stock assessment techniques (Patterson & Melvin 1996). techniques (Patterson & Melvin 1996).

GFCM – Izmir 2008GFCM – Izmir 2008

The FisheryThe Fishery

Purse seine fleetPurse seine fleet

No purse

seines

Gross Tonnage (GT*)

Horse Power

(kW)

Mean fleet age

Average length

Greece 291 11.626 52.038 25 19

GFCM – IzmirGFCM – Izmir 20082008

>95% responsible for anchovy and sardine catches in Greek waters

Technical measures: Fishing practices, fishing seasons Technical measures: Fishing practices, fishing seasons & areas, effort, gear regulations& areas, effort, gear regulations

Closed period (mid December – end of February)Closed period (mid December – end of February) Minimum distance from shore 300m or 30m bottom depthMinimum distance from shore 300m or 30m bottom depth Minimum no of lamps per vessel (6)Minimum no of lamps per vessel (6) Min landing size (anchovy: 9 cm, sardine: 11 cm)Min landing size (anchovy: 9 cm, sardine: 11 cm) Min mesh size (40 mm for purse seines working daytime, Min mesh size (40 mm for purse seines working daytime,

14 mm for purse seines working nighttime)14 mm for purse seines working nighttime)

GFCM – Izmir GFCM – Izmir 20082008

Data usedData used

Purse seine fishery in North Aegean Sea (main Purse seine fishery in North Aegean Sea (main fishing grounds for anchovy and sardine in fishing grounds for anchovy and sardine in Aegean Sea)Aegean Sea)

Annual anchovy and sardine landingsAnnual anchovy and sardine landings 2000-20062000-2006 HCMR data collection system, several national & HCMR data collection system, several national &

EU projects of HCMR & FRIEU projects of HCMR & FRI Data from 2003 onward were collected within the Data from 2003 onward were collected within the

framework of the framework of the Greek National Fisheries Data Greek National Fisheries Data Collection programCollection program


DataData

Data were collected on a seasonal basisData were collected on a seasonal basis Measurements: Total length, biological sampling Measurements: Total length, biological sampling

(weight, otoliths: age reading, gonads for maturity (weight, otoliths: age reading, gonads for maturity estimates)estimates) Age sampling: Age sampling:

separate length and age sampling or separate length and age sampling or representative age sampling. representative age sampling.

Landings were grouped by length classes (1 Landings were grouped by length classes (1 cm) and applied on a yearly basis to ALK.cm) and applied on a yearly basis to ALK.

GFCM – Izmir GFCM – Izmir 20082008

Biological information used as input for the model:Biological information used as input for the model:

Maturity-at-age:Maturity-at-age: based on biological samples based on biological samples from commercial and research vessels from commercial and research vessels collected during the spawning seasoncollected during the spawning season

Natural mortalityNatural mortality: fixed parameter over years : fixed parameter over years and ages (M=0.7 anchovy, M=0.8 for sardine, and ages (M=0.7 anchovy, M=0.8 for sardine, based on acoustic estimates (No ind/ age based on acoustic estimates (No ind/ age group) group)

Reference age for the fishery Reference age for the fishery age group 2 age group 2 (fully exploited & fully recruited)(fully exploited & fully recruited)


Weighting factors regarding catchesWeighting factors regarding catches

Ages 0 and 4 were downweighted (0.01), considered Ages 0 and 4 were downweighted (0.01), considered marginal marginal in terms of their percentage in the catch in terms of their percentage in the catch (< (< 5% and 1% respectively)5% and 1% respectively)

Age 3 was downweighted (0.3) represented 6% in the Age 3 was downweighted (0.3) represented 6% in the catchcatch

Six years separable constrainSix years separable constrain Reference age for the fishery Reference age for the fishery age group 2 age group 2 (fully (fully

exploited & fully recruited)exploited & fully recruited) Mean F Mean F for agesfor ages 1 to 3+ 1 to 3+ was estimatedwas estimated


Total anchovy landings

R2 = 0.8481

0

5000

10000

15000

20000

25000

2000 2001 2002 2003 2004 2005 2006

Year

Ca

tch

es

(t)


Anchovy


Total sardine landings

R2 = 0.2186

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

2000 2001 2002 2003 2004 2005 2006

Year

Ca

tch

es

(t)

Sardine

Tuning indicesTuning indices(fishery independent surveys)(fishery independent surveys)

38o

39o

40o

41o

22o 23o 24o 25o 26o

Thermaikos Gulf

38o

39o

40o

41o

22o 23o 24o 25o 26o

Thermaikos Gulf


1

51

101

151

201

251

301

351

401

451

501

551

601

651

701

39.00

40.00

41.00

23.00 24.00 25.00 26.00

Total Biomass (acoustics)Total Biomass (acoustics) Stock Spawning biomass (DEPM)Stock Spawning biomass (DEPM)

Anchovy

0

10000

20000

30000

40000

50000

60000

70000

80000

2003 2004 2005 2006

Bio

ma

ss

(t)

Acoustics TSB DEPM SSB


Tuning indicesTuning indices(fishery independent surveys)(fishery independent surveys)

38o

39o

40o

41o

22o 23o 24o 25o 26o

Thermaikos Gulf

38o

39o

40o

41o

22o 23o 24o 25o 26o

Thermaikos Gulf

Total Biomass (acoustics)Total Biomass (acoustics)

Sardine

Acoustics TSB

0

10000

20000

30000

40000

50000

60000

2003 2004 2005 2006

Bio

mas

s (t

)

Anchovy population structure per age group

0

1000000

2000000

3000000

4000000

5000000

6000000

2003 2004 2005 2006Year

No

of

fis

h in

th

ou

sa

nd

s

Age1

Age2

Age3+

Population statusPopulation status


Major component of the stock:

1-year-old and 2-year-old fish

Sardine population structure per age group

0

200000

400000

600000

800000

1000000

1200000

2003 2004 2005 2006Year

No

of

fis

h in

th

ou

sa

nd

s

Age1

Age2

Age3+

Length frequency distribution…Length frequency distribution…

2 sub-areas: 2 sub-areas: East areaEast area (Thracian Sea (Thracian Sea

and Strymonikos Gulf) and Strymonikos Gulf) Shift towards smaller length Shift towards smaller length

classes in 2005 & 2006classes in 2005 & 2006

West areaWest area (Thermaikos (Thermaikos and Evoikos Gulfs)and Evoikos Gulfs) Shift towards smaller length Shift towards smaller length


Anchovy

East Area

0

5

10

15

20

25

30

35

52.5

62.5

72.5

82.5

92.5

102.5

112.5

122.5

132.5

142.5

152.5

162.5

172.5

182.5

%

2003

2004

2005

2006

West Area

0

5

10

15

20

25

30

35

52.5

62.5

72.5

82.5

92.5

102.5

112.5

122.5

132.5

142.5

152.5

162.5

172.5

182.5

Length (mm)

%


(population)

Length frequency distribution…Length frequency distribution…

Sardine

East Area

0

5

10

15

20

25

30

35

40

45

52.5 67.5 82.5 97.5 112.5 127.5 142.5 157.5 172.5 187.5

%

2003

2004

2005

2006

West Area

0

5

10

15

20

25

30

35

40

45

52.5 67.5 82.5 97.5 112.5 127.5 142.5 157.5 172.5 187.5

Length (mm)

%

2 sub-areas: 2 sub-areas: East areaEast area (Thracian Sea (Thracian Sea

and Strymonikos Gulf)and Strymonikos Gulf) Shift towards bigger length Shift towards bigger length


West areaWest area (Thermaikos and (Thermaikos and

Evoikos Gulfs)Evoikos Gulfs) Shift towards bigger length Shift towards bigger length

classes in 2006classes in 2006


(population)


Anchovy Assessment Model: DEPM Absolute_Acoustic Anchovy Assessment Model: DEPM Absolute_Acoustic Linear according to WGMHSA 2005 suggestionLinear according to WGMHSA 2005 suggestion

Age Residuals

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

0 1 2 3 4

Age

Mar

gin

al T

ota

l

Year Residuals

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

2003 2004 2005 2006

Year

Mar

gin

al T

ota

l


Anchovy Assessment Model results (DEPM Anchovy Assessment Model results (DEPM Absolute_Acoustic Linear according to WGMHSA Absolute_Acoustic Linear according to WGMHSA 2005 suggestion)2005 suggestion)

Population Population statusstatusStock size

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

2000 2001 2002 2003 2004 2005 2006

Year

Bio

mas

s

Total Spawning

Recruitment

0

5000000

10000000

15000000

20000000

2000 2001 2002 2003 2004 2005

Year

Rec

ruit

s


Fishing Mortality

0

1

2

3

2000 2001 2002 2003 2004 2005 2006

Year

Ref

eren

ce F

Fishing mortality

0

0.2

0.4

0.6

0.8

2000 2001 2002 2003 2004 2005 2006

Year

Mea

n F

Exploitation rate

0

0.2

0.4

0.6

2000 2001 2002 2003 2004 2005 2006

Year

F/Z

Aegean anchovy stock

Reference point

Fishing mortality remains more or less at the same level

Exploitation rate < 0.4 since 2003

ResultsResults

Preliminary resultsPreliminary results because of small time because of small time seriesseries

Stock characterized by intermediate Stock characterized by intermediate abundances, abundances, fully exploitedfully exploited, with high fishing , with high fishing mortality ratesmortality rates

Exploitation rate Exploitation rate belowbelow the empirical level the empirical level for stock declinefor stock decline (0.4, Patterson 1992). (0.4, Patterson 1992).

Signs of recovery regarding Signs of recovery regarding E,E, SSBSSB and and RecruitmentRecruitment in 2006 in 2006

Reference pointsReference points can only can only cautionarycautionary suggested assuggested as TBlim=31800 t (CV=0.109), estimated in 2005.TBlim=31800 t (CV=0.109), estimated in 2005. SSBlim=20500 t (CV=0.170), estimated in 2005.SSBlim=20500 t (CV=0.170), estimated in 2005. SSBpa=30750 t (as SSBlim*1.5)SSBpa=30750 t (as SSBlim*1.5)



Sardine Assessment Model: Acoustic LinearSardine Assessment Model: Acoustic Linear

Year Residuals

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

2003 2004 2005 2006

Year

Mar

gin

al T

ota

l

Age Residuals

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

0 1 2 3 4

Age

Mar

gin

al T

ota

l


Population Population statusstatus

Sardine Assessment Model results (Acoustic Linear Sardine Assessment Model results (Acoustic Linear according to WGMHSA 2005 suggestion)according to WGMHSA 2005 suggestion)

Recruitment

0

2000000

4000000

6000000

2000 2001 2002 2003 2004 2005 2006

Year

Re

cru

its

Stock size

0

10000

20000

30000

40000

50000

60000

70000

80000

2000 2001 2002 2003 2004 2005 2006

Year

Bio

mas

s

Total Spawning


Fage-2 remains more or less at the same level

Mean F1-3 shows decreasing trend

Exploitation rate > 0.4

Exploitation rate

0

0.2

0.4

0.6

0.8

2000 2001 2002 2003 2004 2005 2006

Year

F/Z

Aegean sardine stock

Reference point

Fishing mortality

0

0.3

0.6

0.9

1.2

1.5

2000 2001 2002 2003 2004 2005 2006

Year

Mea

n F

Fishing Mortality

0

1

2

3

4

5

6

2000 2001 2002 2003 2004 2005 2006

Year

Re

fere

nc

e F


ResultsResults

Preliminary resultsPreliminary results because of small time series because of small time series Stock characterized by intermediate abundances, Stock characterized by intermediate abundances,

fully exploitedfully exploited, with high fishing mortality rates, with high fishing mortality rates Exploitation rate Exploitation rate aboveabove the empirical level for the empirical level for

stock declinestock decline (0.4, Patterson 1992) (0.4, Patterson 1992) Signs of recovery regarding Signs of recovery regarding TBTB and and RecruitmentRecruitment

in 2006in 2006 Reference pointsReference points can only can only cautionarycautionary

suggested assuggested as TBlim=13800 t (CV=0.354), estimated in 2004.TBlim=13800 t (CV=0.354), estimated in 2004.

Management suggestionsManagement suggestions

Small pelagics abundances and recruitment are highly Small pelagics abundances and recruitment are highly variable due to environmental conditionsvariable due to environmental conditions

So,So, Monitoring through fishery independent surveysMonitoring through fishery independent surveys Not increase fishing effortNot increase fishing effort

Shift of the closed periodShift of the closed period (present: mid December (present: mid December to end of February) towards the post recruitment to end of February) towards the post recruitment period of anchovy (e.g. October to December) or period of anchovy (e.g. October to December) or the post recruitment period of sardine (e.g. the post recruitment period of sardine (e.g. February to April)February to April)


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GIANNOULAKI M., SOMARAKIS S., MACHIAS A., SIAPATIS A., PAPACONSTANTINOU C. Hellenic Centre for...

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