total egg production in trisopteurs luscus: effect of stock structure copia
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Total egg production in Trisopteurs luscus:
effect of stock structure
Alexandre Alonso-Fernández and Fran Saborido-Rey
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Introducció n
HypothesisThe Stock Reproductive Potential (SRP) is affected by population estructure through the total egg production of the female Spawning Stock Biomass (SSB).
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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?
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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
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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
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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.
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Marshall et al. 1998; Kraus et al. 2002; Marteinsdottir and Begg 2002; ...
Introducció n
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“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
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995 tons>1.7 millon euros
Trisopterus luscus (Linnaeus 1758)
http://www.pescadegalicia.com
4Introducció n
pouting
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Trisopterus luscus (Linnaeus 1758)5
Introducció n
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Material and Methods
Sampling
Atlantic Ocean
Mediterranean Sea
Vigo
Ribeira
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•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
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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
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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)
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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
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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
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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
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Results and Discussion
Egg quality
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Results and Discussion
877 x 109
1384 x 109
1854 x 109
3373 x 109
Determinate Indeterminate
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Results and Discussion
IndeterminateIndeterminate
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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.
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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.
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Thank you