Total egg production in Trisopteurs luscus:

effect of stock structure

Alexandre Alonso-Fernández and Fran Saborido-Rey

Introducció n

HypothesisThe Stock Reproductive Potential (SRP) is affected by population estructure through the total egg production of the female Spawning Stock Biomass (SSB).

1

Objectives Elaborate a model of total stock egg production

from empirical data• Is SSB proportional to SRP?• How does the model respond under different

fecundity assumptions?

Stock Reproductive Potencial in stock assessment

Stock/Recruitment relationships

Represent the fundamental relationship between parental and offspring population=>basic tool in actual fisheries management.

2Introducció n

Stock Reproductive Potencial in stock assessment

Stock/Recruitment relationships

Represent the fundamental relationship between parent and offspring population=>basic tool in actual fisheries management.SSB is the traditional indicator of the reproductive capacity of the population.

2Introducció n

Stock Reproductive Potencial in stock assessment

Stock/Recruitment relationships

Represent the fundamental relationship between parent and offspring population=>basic tool in actual fisheries management.SSB is the traditional indicator of the reproductive capacity of the population.

2

Marshall et al. 1998; Kraus et al. 2002; Marteinsdottir and Begg 2002; ...

Introducció n

3

“Stock Reproductive Potential” (SRP): “the annual variation ina stock’s ability to produce viable eggs and larvae that mayeventually recruit to adult population or fishery” (Trippel 1999)

¿SSB a good estimator of SRP?Kjesbu et al. 1991; Solemdal 1997; Marshall et al. 1998; Vallin and Nissling 2000;; …

Flemish Cap Cod (Saborido Rey et al. 2004)

Introducció n

995 tons>1.7 millon euros

Trisopterus luscus (Linnaeus 1758)

http://www.pescadegalicia.com

4Introducció n

pouting

Trisopterus luscus (Linnaeus 1758)5

Introducció n

Material and Methods

Sampling

Atlantic Ocean

Mediterranean Sea

Vigo

Ribeira

6

•Dec 2003-Dec 2006

•n=2099

•Total length, total weight and gutted weight, and gonad weight.

•Gonad in formol => histology and fecundity

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Sampling

Material and Methods

Fish size range

Histology

8Material and Methods

•Central portions of the fixed ovaries were extracted, dehydrated, embedded in paraffin, sectioned at 3 m and stained with H&Eμ

Histology

8Material and Methods

•Central portions of the fixed ovaries were extracted, dehydrated, embedded in paraffin, sectioned at 3 m and stained with H&Eμ

(Brown-Peterson et al. 2011)

9Material and Methods

Fecundity estimation

Determinate vs Indeterminate(Hunter et al. 1989; Hunter et al. 1992; Murua and

Saborido-Rey 2003)

•GravimétricoManualImage Analysis

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Results and Discussion

Reproductive Output (Total egg production, TEP)

Traditional approach

SSB = ∑ (N * W * SR * M) l

Is SSB proportional to SRP? How does the model respond under different

fecundity assumptions?

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Results and Discussion

Is SSB proportional to SRP? How does the model respond under different

fecundity assumptions?

Egg production

Reproductive Output (Total egg production, TEP)

Egg production Model

TEP = ∑(N * EP * SR * M ) l

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Results and Discussion

Egg production Model

Determinate

TEPdet = ∑[N * (PF - AL) * SR * M]l

Indeterminate

TEP indet = ∑[N * (BF * NB) * SR * M]l

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Results and Discussion

Egg production ModelDeterminate

TEPdet = ∑[N * (PF - AL) * SR * M]l

Potential Fecundity = 4.718e-06·Length4.397

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Results and Discussion

SSB

TEPWeight = 7E-06Length3.087 Potential Fecundity = 4.718e-06·Length4.397

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Results and Discussion

Egg production ModelDeterminate

TEPdet = ∑[N * (PF - AL) * SR * M]l

15

Results and Discussion

Egg production ModelIndeterminate

TEP indet = ∑[N * (BF * NB) * SR * M]l

Batch Fecundity = 0.003·Length2.710

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Results and Discussion

Egg production ModelIndeterminate

TEP indet = ∑[N * (BF * NB) * SR * M]l

Number of Batches

Spawning frequency

Length of spawning season

S ~ 3, captivity experiment (Alonso-Fernández et al. 2010)

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Results and Discussion

Length of spawning season

Onset

Final

Alonso-Fernández and Saborido Rey, In press

17

Results and Discussion

Length of spawning season

Alonso-Fernández and Saborido Rey, In press

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Results and Discussion

SSB

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Results and Discussion

877 x 109

1384 x 109

1854 x 109

3373 x 109

Determinate Indeterminate

20

Results and Discussion

Egg quality

21

Results and Discussion

877 x 109

1384 x 109

1854 x 109

3373 x 109

Determinate Indeterminate

21

Results and Discussion

IndeterminateIndeterminate

22

Conclusions

IndeterminateIndeterminate A truncated size distribution of the population can produce considerably lower total egg production. A balanced population size structure may contribute to preserve a suitable stock reproductive potential.

23

Conclusions

IndeterminateIndeterminate Proper knowledge of the oocyte recruitment process is required to avoid misestimating egg production. And also reproductive parameter estimation can have an important effect on the accuracy of our egg production estimations.

Thank you