1. Scientific Advisory Committee (SAC) Sub-Committee on Stock Asssessment (SCSA) Working Group on Demersal Species Izmir, Turkey, 15-19 September, 2008 Stock assessment of hake in GSAs 15 and 16 F. Fiorentino, M. Dimeck, M.T. Spedicato, A. Abella, P. Accadia, V. Gancitano

2. The aim of this paper is: To compare assessments of hake done with different approaches and data deriving from indirect (fisheries monitoring) and direct (scientific surveys) sources in the investigated area; To evaluate the use of different biological reference points in order to recommend fishery advices.

3. The yield and abundance in GSA 16……

4. Landing data from GSA 15

6. An attempt of VPA under steady state assumptions with landings information of 2006 and 2007 in GSA 16 winVIT by winVIT package FemalesMalesTotal Observed Yield (tons)…… …….. 1598 Reconstructed Yield (tons)7968021597 Recruits at 12 cm TL (millions)13.521.234.7 Mean Z0.6590.859 Mean F0.3190.429 Global F0.6560.690 Catch mean length (cm)21.119.9 Stock mean length (cm)21.117.7

7. Catch and fishing mortality by size of hake (F & M) Mean Yield and LDF of landings of 2006 and 2007 _GSA 16 by winVIT Package and scalar M

8. Y/R and SSB/R analysis vs Factor of current fishing mortality of hake (F & M) with winVIT Package. Current status

9. SexStatusFactorY/RB/RSSB Females F(Virgin)001390.5921112.604 F(0.1)0.3865.425502.741353.431 F(Max)0.5467.996346.98228.03 F(Current)1.0158.968123.60960.647 F(Double)240.40629.0364.488 Males F(Virgin)00424.559315.641 F(0.1)0.4038.298130.87973.994 F(Max)0.6240.20180.88437.028 F(Current)1.0137.82742.4112.124 F(Double)230.88719.5282.109 Diagnosis from winVIT package…….. …overfishing…

10. Y/R and SSB/R analysis vs Factor of current fishing mortality of hake (F & M) with Yield Package. GSA 15 & 16

11. Main BRPs obtained by Yield package for hake in GSA 15 & 16 Yield based RPfemalemale F based RPfemalemale Y/R max 59.6 39.8 F max 0.244 0.315 Y/R F0.1 57.4 37.4 F 0.1 0.1570.194 Y/R SPR_0.35 59.5 37.8 F SPR_0.35 0.154 0.202 Diagnosis from Yield package……..

12. ….and Surba analysis……

13. What is the current exploitation of hake? According to the Y/R and trawl surveys mortalities … the stock is ….overfished……… and to reach a target such as F0.1….. the reduction of current F should be of about 60% MethodFRemarks B & H estimator on MEDITS data 2005-2006-2007 0.76Minimum length of fully recruitment (L’) of 18 cm TL (Females) Surba on MEDITS data Mean of 2005 and 2006 0.70Mean of age class 1-4 (Combined sex)

14. Other analythical approaches… The recostruction of hake landings fin the GSA 16 by ALADYM Model………..

15. Some management scenarios for GSA 16 based on ALADYM model…………..

18. What about the stock status according to “global” approaches? Equilibrium composite biomass dynamic models Zmbp=1.161459=0.5*(Boo/b') MBP'=31.56166MBP=K/2*Zmbp Electronic sheet by A. Abella

19. Non equilibrium biomass dynamic models Electronic sheet by A. Abella

21. ApproachDataPeriodCurrent point Reference pointDiagnosis VITBiological samplings of landings 2006- 2007 F*=0.66 (Females) F max =F*× 0.54=0.35 F 0.1 =F*×0.38=0.25 O; -46% O; -62% Yield & SurbaTrawl surveys 2005- 2006 F=0.70 (combine d sex) F max = 0.24 F 0.1 = 0.16 F SPR=0.3 = 0.15 O; -55% O; -71% Yield & B_H estimator Trawl surveys 2005- 2007 F=0.76 (Females) F max = 0.24 F 0.1 = 0.16 F SPR=0.3 = 0.15 O; -65% O; -78% Surplus Production Composite Trawl surveys 2005- 2006 Z=1.18 (combine d sex) Z MBP (Schaefer)=1.16 Z MBP (Fox)=0.89 EOEO Non – equilibrium Surplus production Trawl surveys 2005- 2006 Z=1.18 (combine d sex) Z MBP = 0.87 F MBP = 0.39 O O; -44% Recommendation – reduce fishing mortality at least of 44%