Spawning stock biomass of the North Western Mediterranean anchovy in 2007

I. Palomera, L. Recasens, P. Libori, I. Alvarez, B. Molí, N. BahamónInstitut de Ciències del Mar (ICM) CSIC. Passeig Marítim, 37-49. 08003 Barcelona, Spain

GENERAL FISHERIES COMMISSION FOR THE MEDITERRANEANSCIENTIFIC ADVISORY COMMITTEE

Sub-Committee for Stock AssessmentWorking Group on Small Pelagic Species

Izmir, 22-26 September 2008

GSA 7

GSA 6

Gulf of Lions

Rhône Estuary

Ebre River Delta

Catalan Sea

Gul

f of V

alen

cia

Cape Creus

Cape La Nao

FRANCE

SPAIN

DEPM to evaluate the biomass of the anchovy stock has been applied in North Western Mediterranean

Two GSAs are included in the area prospected: GSA6 Gulf of Lions

and GSA7 Northern Spain

The anchovy stock in the Western part of GSA 7 is shared by the

French and the Spanish fishery.

0

5000

10000

15000

20000

25000

Year

Lan

din

gs

(t)

Catalan sea

Gulf of Lions

• Landings in Spanish ports (Catalan sea) increased from late 80’s until early 90’s and decreased thereafter. The highest catches in the area were obtained during 1993 and 1994. This was mainly due to an increase of the fishing effort due to the concentration of vessels coming from another Spanish regions (e.g. Alboran Sea). Since 2005 anchovy landings in the Catalonia ports have decreased below 4000 t (1839 t in 2007).

• Anchovy landings in the Gulf of Lions increased during the late 80s reaching a maximun in 1997 (10000 t); since then it has slightly been decreasing until nowadays, reaching values similar to those obtained in the early 80s

• A partial closure (two months per sub-area) of the purse seine fleet during autumn and winter months started in 1993 in Catalan ports.

Evolution of the fishery

Biomass and production of anchovyin the gulf of Lion

0

20000

40000

60000

80000

100000

120000

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

YearsB

iom

ass

and

pro

du

ctio

n(M

T)

Biomass

Biom - Sd

Biom + Sd

Production

Biomass evolution: Acoustic estimation

Gulf of Lions – GSA 7 Summer cruises

IFREMER data (SCSA 2007)

• Increasing trend that reached its maximum in 2001 (112000 t). After this year the biomass strongly decreasing to 18500 t in 2007 (Liorzou, pers. com.)

Northern Spain - GSA 6Autumn cruises

IEO data (SCSA 2007

• Although this evaluation is mainly concentrated in recruits, the trend seems to coincide with the stock in the Gulf of Lions, with a maximum value also in 2001 (31279 t) decreasing to 4906 t in 2007 (Giraldez, perss. com.)

The DEPM model

B = (k . P . A . W )/( R . F . S)

B = spawning stock biomass in metric tons, k = conversion factor from grams to metric tons, P = daily egg production (number of eggs per sampling unit, m2), A = total survey area (in sampling units, m2), W = average weight of mature females (grams), R = sex ratio (fraction of mature females by weight), F = batch fecundity (mean number of eggs per mature females per spawning), S = fraction of mature females spawning per day (spawning frequency)

DEPM – Anchovy GSAs 6 and 7 - 2007

Egg survey Adult sampling

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.440

40.2

40.4

40.6

40.8

41

41.2

41.4

41.6

41.8

42

42.2

42.4

42.6

42.8

43

43.2

43.4 M35

M57

M64

P9

P10P11

P13

P14P15

P16

P17P18

P19P20

P21

P22P25

P28

B1

B2B3

B4

B5

B6

B7B8

B9

B10B11

B12B13

B14

B15B16

T1

T2

T3T4

T5T6T7T8

A d u lt A n ch o v y S a m p lin g

Ju n e - Ju ly 2007

MPOCAT 0711 – 25 June 2007

MPOCAT 0711 – 25 June 2007

•326 plankton samples

•126 CTD profiles

• 40 adult samples:

16 pelagic trawl (M, P)

24 purse seine (B, T)

PARAMETERS

P, A R, F, W, S

Egg Production-------------------Spawning area

Abundance and distribution of anchovy eggs obtained during the sampling cruise MPOCAT07. Points indicated sampling stations and circles relative abundances of eggs.

1.340.000 millions-------------------

13.740 km2

-------------------

180.000 millions-------------------

11.338 km2

-------------------

EGG PRODUCTION, P0 – SPAWNING AREA, A

All Area North South

P0

(eggs/m2/day)CV

57,650.202

97,890.262

15,900.251

z (egg mortality) 0.48 0.58 0.20

Range of temperatures at 10

m (0 C)16.8-21.8 16.8-21.7 17.6-21.8

P0 whole area

(eggs/day) x (1012)CV

1.440.202

1.340.262

0.180.251

-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4

38.6

38.8

39

39.2

39.4

39.6

39.8

40

40.2

40.4

40.6

40.8

41

41.2

41.4

41.6

41.8

42

42.2

42.4

42.6

42.8

43

43.2

43.4

43.6

43.8

44

0 to 1

1 to 100

101 to 200

200 to 500

501 to 1000

200 m

1000 m

Ous SeitoJuny 2007

(nº/m2)

Anchovy Eggs

June 2007

DEPM Parameters All Area North South

P0

(eggs/m2/ per day)57.65(0.20)

97.89(0.26)

15.90(0.25)

A(km2) 25058.63 13740.33 11338.16

W(average female weight in g)

23.74(0.04)

22.65(0.03)

26.42(0.02)

F(batch fecundity)

9101.29(0.11)

8746.51(0.08)

9968.90(0.08)

S(spawning fraction/day)

0.29(0.05)

0.29(0.05)

0.29(0.05)

R(fraction of mature females)

0.58(0.04)

0.54(0.04)

0.54(0.05)

BIOMASS(T)

24014.59(0.23)

20849.22(0.18)

3046.87(0.26)

Parameter obtained for anchovy spawning biomass estimation through DEPM in the North Westrern Mediteranean during the peack spawning of 2007 and resulting biomass obtained. Between brackets the coefficient of variation of each parameter.

ANCHOVY DEPM PARAMETERS 2007

COMPARISON WITH PREVIOUS DEPM ESTIMATES

1993 and 1994 ----- 2007

1993 1994 2007

North(Gulf of Lions + North

Catalan sea)

P0 (*) 96.39 97.89

A1 24568 18830 13740

South(South Catalan sea + Gulf

of Valencia)

P0 58.18 88.40 15.90

A1 9454 12862 11338

All AreaP0 64.22 61.53 57.65

A1 33012 31692 25059

* Not possible to derive the North data from the available data

Egg Production-------------------Positive Area

1.340.000 millions-------------------

1.680.000 millions-------------------

13.740 km2

-------------------18.830 km2

180.000 millions-------------------

1.040.000 millions-------------------

11.338 km2

-------------------12.862 km2

Spawning area and Egg Production comparison

-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4

38.6

38.8

39

39.2

39.4

39.6

39.8

40

40.2

40.4

40.6

40.8

41

41.2

41.4

41.6

41.8

42

42.2

42.4

42.6

42.8

43

43.2

43.4

0 to 0

1 to 100

101 to 200

201 to 500

501 to 1000

1001 to 2000

200 m

1000 m

Juny 1994

-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4

38.6

38.8

39

39.2

39.4

39.6

39.8

40

40.2

40.4

40.6

40.8

41

41.2

41.4

41.6

41.8

42

42.2

42.4

42.6

42.8

43

43.2

43.4

200 m

1000 m

Ous Seito

Juny 2007

0 to 0 .1

1 to 100

101 to 200

201 to 500

501 to 1000

Anchovy eggsJune 2007

June 1994

BIOMASS (t) 1993 1994 2007

%Reductio

n(*)

North(Gulf of Lions + North

Catalan sea)

22427(0.35)

42846(0.41)

20849(0.23) 34

South(South Catalan sea +

Gulf of Valencia)

8422(0.43)

11044(0.43)

3047(0.18) 69

All Area30849(0.30)

52557(0.36)

24015(0.26) 42

COMPARISON WITH PREVIOUS DEPM ESTIMATES

1993 and 1994 ----- 2007

(*) 2007 Biomass reduction in comparison with the average values of 1993 and 1994

CONCLUSIONS

1. The anchovy spawning biomass in the North Western Mediterranean Sea, GSAs 6 and 7 was estimated by means of the DEPM. Biomass estimate was 24000 tons in the whole area, from these 20849 t were from the Northern spawning stock and 3050 t f rom the Southern spawning stock.

2. The low biomass estimate in the Southern area in addition to the fact that the spawning area extension is similar to the Northern one, allows us to infer that this year the anchovy population in the Southern area was very widespread and hence less accessible to the fishing vessels.

3. Comparisons of the present results to those obtained in 1993 and 1994 by the same method, indicated an important decrease in anchovy biomass and also in egg production, specially in the southern area.

4. The situation of the Gulf of Lions stock found by the acoustic analysis done by IFREMER also showed a continuous decrease, being an 84% lower nowadays compared to 2002. In addition, the results found by IEO acoustic estimates showed a decreasing trend in the recruitment since 2001 with a slight recovery in 2006, that has not been detected in the 2007 landings.

5. These results together with the poor fisheries results for the past years allow us to consider that the anchovy stock in the North Western Mediterranean might be in a critical situation, specially in the southern area.

6. Although it not exist any point of reference on the minimum sustainable biomass for anchovy in the North Western Mediterranean, everything seems to indicate that the stock might be at risk with a reduced reproductive capacity.

7. Moreover, it is unlikely that a small size stock like the present one could have a strong recruitment, mostly if we consider the well documented cases about the quick influence that any environmental variation can have on small pelagic fish populations.

MANAGEMENT RECOMMENDATIONS

To close the anchovy fishery in the GSA 6, at least until the

recruitment levels obtained by scientific studies do not reach the same levels as in 2003 (20000 t as Reference level).

Followed with a reduction of the fishing effort, and

To increase the anchovy fishing allowable size to 11 cm.

To establish assessment rules between French and Spanish governments directed to preserve the shared anchovy stocks in the GSA 7 (Gulf of Lions).

THANKS FOR YOUR ATTENTION

and

THANKS STELIOS FOR THE PRESENTATION