GFCM-SACSubCommittee on Stock Assessment (SCSA)

Izmir, 22-26 September 2008

ANCHOVY AND SARDINE STOCK ASSESSMENT IN THE GSA 17: 1975-2007

Santojanni A. 1a , Cingolani N. 1a , Donato F. 1a , Colella S. 1a ,Berlardinelli A. 1a , Giannetti G. 1a , Leonori I. 1b ,

Sinovcic G. 2 , Marceta B. 3

1a CNR-ISMAR-SPM, Fish Population Dynamics Unit, Ancona (Italy)

1b CNR-ISMAR-SPM, Marine Acoustics Unit, Ancona (Italy)

2 Institute of Oceanography and Fisheries, Split (Croatia)

3 Fisheries Research Institute of Slovenia, Ljubljana (Slovenia)

Anchovy(Engraulis encrasicolus)

Sardine(Sardina pilchardus)

Mid-water trawlersItaly 2007: about 60 pairs

Purse seiners attracting fish by lightItaly 2007: 40-50 vessels (including “small” and “high” tonnage)

Fishery

Mid-water trawlers

Purse seiners

Data collection

since 1975

still ongoing:

- catches

- fishing effort

- length, weight of fish

- age (otolith readings)

12.00 13.00 14.00 15.00

43.00

44.00

45.00

46.00

T ries te G rado

M aranoL agunare

C aor le

C h iogg ia

G oro

R avenna

C esena tico

R im in i

C atto lica

F ano

A ncona

P.C iv itanova

P.S anG io rgio

S .B enede tto

G iulianova

6 0

1 0 0

2 0 0

4 0

G ariba ldiP orto

Hauls sampled by the observer on board of Italian fishing vesselsSantojanni et al. (2005) - Scientia Marina

Geo-referenced small pelagic catch per haul collected by means of electronic logbooks on board of fishing vessels

Virtual Population Analysis (VPA)

based on Laurec-Shepherd tuning

on abundance index derived from echo-survey.

Software:Darby C.D., Flatman S. 1994. Virtual Population Analysis: version 3.1 (Windows/Dos) user guide. Information Technology Series, MAFF Directorate of Fisheries Research, Lowestoft, 1: 85 pp.

Structure of the data used:

Split-year data were used assuming the first of June as the birth date of anchovy.

Calendar-year data were used for sardine.

Anchovy total catch

Sardine total catch

0

10000

20000

30000

40000

50000

60000

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Split year

Ca

tch

(to

nn

es

)

Slovenia and CroatiaItaly

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

Ca

tch

(to

nn

es

)Slovenia and CroatiaItaly

Age frequency distribution of the total catch

25.1

40.2

21.7

9.1

3.00.9 0.1

0

5

10

15

20

25

30

35

40

45

Age 0 Age 1 Age 2 Age 3 Age 4 Age 5 Age 6

% Average 1976-2007

4.50

23.6125.05

20.23

14.85

6.68

3.120.94 0.63 0.28 0.10 0.01 0.00

0

5

10

15

20

25

30

Age0

Age1

Age2

Age3

Age4

Age5

Age6

Age7

Age8

Age9

Age10

Age11

Age12

% Average 1975-2007

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Split-year

Age 4

Age 3

Age 2

Age 1

Age 0

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

Age 6+

Age 5

Age 4

Age 3

Age 2

Age 1

Age 0

Abundance at sea from echo-survey

Stock biomass

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

To

nn

es

Stock biomass

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

To

nn

es

Sardine

Anchovy

Natural mortality rate M

AnchovyM = 0.6 and M = 0.8 on the basis of

- values in the literature

- the highest values of life span in our data are 4, 5, 6 years

- precautionary approach for M = 0.6

SardineM = 0.5 on the basis of

- values in the literature

- the highest values of life span in our data are 10, 11, 12 years

Anchovy: M = 0.54 and M = 0.81 were reported for the Catalan Sea by Pertierra and Lleonart (1996).

Sardine: M = 0.5 was obtained in the Adriatic Sea by Sinovcic (1986). Values of M from 0.29 to 0.62 were reported for the Catalan Sea by Pertierra and Perrotta (1993).

The criterion to select M taking into account the inverse relationship between Z and longevity was adopted for small pelagics by other authors. As reported in a recent GLOBEC report (Barange, 2001), Pacific sardine (Sardinops sagax) is usually assumed to have a relatively low annual natural mortality rate, M = 0.4, and a lifespan of about 10 years, whereas for northern anchovy (Engraulis mordax) M = 0.8 is associated to a lifespan of about 4 years.Barange M. (ed.) 2001. Report of the first meeting of the SPACC/IOC study group on the “Use of environmental indices in the management of pelagic fish populations”, 3-5 September 2001, Cape Town, South Africa. GLOBEC Special Contribution, 5, 122 pp.Pertierra J.P., Lleonart J. 1996. NW Mediterranean anchovy fisheries. Scientia Marina, 60 (Suppl. 2): 257-267.Pertierra J.P., Perrotta R.G. 1993. On the population dynamics of sardine, Sardina pilchardus Walbaum, 1792, from the Catalan Sea (northwestern Mediterranean). Scientia Marina, 57: 235-241.Sinovcic G. 1986. Estimation of growth, mortality, production and stock size of sardine, Sardina pilchardus (Walb.), from the middle Adriatic. Acta Adriatica, 27: 67-74.

Natural mortality rate M

Hoenig’s equation:

Ln Z = 1.44 – 0.982 Ln tmax

“based largely on data from unexploited stocks”,

thus with Z being very close to M.

Hoenig J.M. 1983. Empirical use of longevity data to estimate mortality rates. Fishery Bulletin, 82: 898-903.

Hewitt D.A., Hoenig J.M. 2005. Comparison of two approaches for estimating natural mortality based on longevity. Fishery Bulletin, 103: 433-437.

Natural mortality rate M tmax (year) predicted Z

1 4.22

2 2.14

3 1.43

4 1.08

5 0.87

6 0.73

7 0.62

8 0.55

9 0.49

10 0.44

11 0.40

12 0.37

13 0.34

14 0.32

15 0.30

16 0.28

17 0.26

18 0.25

19 0.23

20 0.22

Natural mortality rate M for sardine

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9Age (years)

Len

gth

(cm

)R square = 0.786

Parameter Value Standard error

Confidence interval at 95%

Lower limit Higher limit

Linf 18.783 0.226 18.339 19.226

k 0.379 0.028 0.324 0.435

t0 -2.302 0.185 -2.665 -1.939

Santojanni et al. (2008): GSA17, year 2007, EU-DCR

0

2

4

6

8

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7 8 9 10 11 12Age (years)

Le

ng

th (

cm

)

Santojanni et al. (2008): Linf=18.78, k=0.38, t0=-2.30

Sinovcic (1986): Linf=20.50, k=0.46, t0=-0.50

M = 1.5 KJensen A.L. 1996. Beverton and Holt life history invariants result from optimal trade-off of reproduction and survival. Canadian Journal of Fisheries and Aquatic Science, 53: 820-822.

Jensen A.L. 2001. Comparison of theoretical derivations, simple linear regressions, multiple linear regression and principal components for analysis of fish mortality, growth and environmental temperature data. Environmetrics, 12: 591-598.

M = 0.57 with 0.38 [Santojanni et al. (2008), otoliths, fitting]

M = 0.69 with 0.46 [Sinovcic (1986), otoliths, Linf and k estimated by Gulland-Holt plot]

F/Z = 0.4 = > F = 2/3 M

Patterson K. 1992.Fisheries for small pelagic species: an empirical approach to management targets. Review of Fish Biology and Fisheries, 2: 321-338.

Anchovy: mid-year stock biomass estimated by VPA

0

100000

200000

300000

400000

500000

600000

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Split-year

To

nn

es

Total catch

Stock biomass (M = 0.6)

Stock biomass (M = 0.8)

Anchovy: comparison between VPA and echo-survey

0

50000

100000

150000

200000

250000

300000

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Split-year (VPA) - Year (Echo-survey)

To

nn

es

Total catch

VPA (M = 0.6)

VPA (M = 0.6): modified agedistribution in the tuning file

0

100000

200000

300000

400000

500000

600000

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Split-year (VPA) - Year (Echo-survey)

To

nn

es

VPA (M = 0.6)

VPA (M = 0.8)

Echo-survey

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007Cohort

age4

age3

age2

age1

age0

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2002 2003 2004 2005 2006 2007

Cohort

age4

age3

age2

age1

age0

Anchovy: results from VPA with M = 0.6Total catch (t) Stock biomass (t) Ratio

Average 1976-2007 27890 122109 0.23

Average 2005-2007 42614 210452* 0.20

Fishing mortality rate F

Unweighted average of Ffor age 0-3

Average1976-2007

0.32

Average2005-2007

0.24

Weighted average of F for age 0-4

Average1976-2007

0.22

Average2005-2007

0.190.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Split-year

FUnweighted average for age 0-3

Weighted average for age 0-4

*182955 with modified age distribution in the t.f.

0.00

0.10

0.20

0.30

0.40

0.50

Age 0 Age 1 Age 2 Age 3 Age 4+

FAverage 1976-2007

Anchovy: exploitation rate from VPA with M = 0.6

0.00

0.10

0.20

0.30

0.40

0.50

0.60

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Split-year

F/ZF/Z (F0-3 unweighted)F/Z (F0-4 weighted)

Threshold (Patterson, 1992)

Average 1976-2007 of F/Z (F0-3 unweighted): 0.34Average 2005-2007 of F/Z (F0-3 unweighted): 0.28

Average 1976-2007 of F/Z (F0-4 weighted): 0.26Average 2005-2007 of F/Z (F0-4 weighted): 0.24

07

05

9089

85

84

87 86

88

82

83

91

968197

9892

80

7779

78

94 95

9399

000102

03

04

06

0

500000

1000000

1500000

2000000

2500000

3000000

0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000

Spawning biomass in year x (tonnes)

Rec

ruits

in y

ear x

+1 (i

ndiv

idua

ls *

10-4

)

Year n+1 specified near the data points

Anchovy stock-recruitment relationship(derived from VPA with M = 0.6)

Sardine: mid-year stock biomass estimated by VPA

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

To

nn

es

Total catch

Stock biomass

Sardine: comparison between VPA and echo-survey

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

To

nn

es

Total catch

Stock biomass (VPA)

Stock biomass (Echo-survey)

Sardine: results from VPATotal catch (t) Stock biomass (t) Ratio

Average 1975-2007 44439 444309 0.10

Average 2005-2007 17489 90928 0.19

Fishing mortality rate F

Unweighted average of Ffor age 0-5

Average1975-2007

0.27

Average2005-2007

0.48

Weighted average of F for age 0-6

Average1975-2007

0.12

Average2005-2007

0.170.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

FUnweighted average for age 0-5

Weighted average for age 0-6

0.00

0.10

0.20

0.30

0.40

0.50

Age0

Age1

Age2

Age3

Age4

Age5

Age6+

FAverage 1975-2007

Sardine: exploitation rate from VPA

0.00

0.10

0.20

0.30

0.40

0.50

0.60

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07

Year

F/Z

F/Z (F0-5 unweighted)

F/Z (F0-6 weighted)

Threshold (Patterson, 1992)

Average 1975-2007 of F/Z (F0-5 unweighted): 0.32Average 2005-2007 of F/Z (F0-5 unweighted): 0.48

Average 1975-2007 of F/Z (F0-6 weighted): 0.19Average 2005-2007 of F/Z (F0-6 weighted): 0.25

Sardine stock-recruitment relationship(derived from VPA)

0705

030201

0099 98

92

9493

77 78

76

7991

97 96

80

95

90

82

8187

85

86

83

8488

89

0406

0

500000

1000000

1500000

2000000

2500000

3000000

0 100000 200000 300000 400000 500000 600000 700000 800000

Spawning biomass in year x (tonnes)

Rec

ruits

in y

ear x

+1 (i

ndiv

idua

ls *

10-4

)

Year n+1 specified near the data points

a)

0

50000

100000

150000

200000

250000

300000

76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 12Anno

To

nn

ella

te

Catture totali F F x 1,3 F x 1,5Biomassa dello stock F F x 1,3 F x 1,5

b)

0

50000

100000

150000

200000

250000

300000

76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 12Anno

To

nn

ella

te

Catture totali F F x 1,3 F x 1,5Biomassa dello stock F F x 1,3 F x 1,5

c)

0

50000

100000

150000

200000

250000

300000

76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 12Anno

To

nn

ella

te

Catture totali F F x 1,3 F x 1,5Biomassa dello stock F F x 1,3 F x 1,5

Simulations of anchovy stock biomass and total catch for the period 2007-2012 from ISMAR report to Italian Ministry

Na+1, t+1 = Na, t exp( –(Fa + M) )

Ca, t = [ Fa / (Fa + M) ] [ 1 – exp( –(Fa + M) ) ] Na, t

M = 0.6

Fa : the level F is the average 1999-2006.

Three scenarios of recruitment:

“high”, “low”, “mixed”.

a)

0

200000

400000

600000

800000

1000000

1200000

75 77 79 81 83 85 87 89 91 93 95 97 99 01 03 05 07 09 11

Anno

To

nn

ella

te

Catture totali F F x 1,3 F x 1,5Biomassa dello stock F F x 1,3 F x 1,5

b)

0

200000

400000

600000

800000

1000000

1200000

75 77 79 81 83 85 87 89 91 93 95 97 99 01 03 05 07 09 11

Anno

To

nn

ella

te

Catture totali F F x 1,3 F x 1,5Biomassa dello stock F F x 1,3 F x 1,5

c)

0

200000

400000

600000

800000

1000000

1200000

75 77 79 81 83 85 87 89 91 93 95 97 99 01 03 05 07 09 11

Anno

To

nn

ella

te

Catture totali F F x 1,3 F x 1,5Biomassa dello stock F F x 1,3 F x 1,5

Na+1, t+1 = Na, t exp( –(Fa + M) )

Ca, t = [ Fa / (Fa + M) ] [ 1 – exp( –(Fa + M) ) ] Na, t

Simulations of sardine stock biomass and total catch for the period 2007-2012 from ISMAR report to Italian Ministry

M = 0.5

Fa : the level F is the average 1999-2006.

Three scenarios of recruitment:

“high”, “low”, “mixed”.

The stock biomass of anchovy dropped at a very low level in 1987. After this collapse, recovery took place, but fluctuations still occurred, in particular in recent years. It should be remembered that strong changes over time are commonly observed in the abundance of small pelagics, in particular anchovies (Jacobson et al., 2001). The recent exploitation rate F/Z was under the Patterson’s threshold 0.4, but on the other hand, an increase was observed in both western and eastern side catches of most recent years: the mentioned average for the period 2005-2007, 42614 tonnes, was quite over the average for the previous years from 1995 to 2004, 27353 tonnes. The stock can be considered as fully exploited.

Jacobson L.D., De Oliveira J.A.A., Barange M., Cisneros-Mata M.A., Felix-Uraga R., Hunter J.R., Kim J.Y., Matsuura Y., Niquen M., Porteiro C., Rothschild B., Sanchez R.P., Serra R., Uriarte A., Wada T. 2001. Surplus production, variability, and climate change in the great sardine and anchovy fisheries. Canadian Journal of Fisheries and Aquatic Science, 58(9): 1891-1903.

Management advice for both species

The most recent values of the exploitation rate F/Z of sardine stock, obtained using unweighted F0-5 , were higher than the Patterson’s threshold 0.4: the average for the period 2005-2007 was equal to 0.48 (0.32 for the whole period). Moreover, a strong decline of stock biomass occurred after the peak in the first half of 1980s; this declines was continuous till the end of 1990s: then, biomass was quite stable around values slightly lower than 100000 tonnes, which corresponded to the lowest abundances of the time series. The stock can be considered as overexploited.

Management advice for both species

It should be noted that Adriatic small pelagic fishery is multispecies and effort on anchovy cannot be separated from effort on sardine, so that most of the management decisions should be taken considering both species. In conclusion, it is recommended not to increase the fishing effort: such an increase would be particularly unwise for sardine.

Management advice for both species