Development of a multi-species model in the Bay of Biscay using the modelling environment GADGET Workshop on “Ecosystem Based Fisheries Management – State.

Development of a multi-species model in the Bay of Biscay using the modelling

environment GADGET

Workshop on

“Ecosystem Based Fisheries Management – State of the Art”

Eider Andonegi27th of March of 2008, Esbjerg (Denmark)

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Structure

• 1. Introduction:– 1.1. Ecosystem approach to fisheries: modelling approaches– 1.2. GADGET – 1.3. Bay of Biscay

• 2. Status of the art:– 2.1. Single-species model for hake

Gadget – VPA results comparison. Predictions (Recovery Plan for European Hake) New growing pattern (de Pontual et al. 2006)

– 2.2. Single-species model for anchovy– 2.3. Preliminary multi-species model (hake eating on anchovy)

Traditional - new growing pattern.

• 3. Things to do

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1.1. Introduction: Modelling approaches

• Ecosystem approach to fisheries (Plagányi, 2007)– Whole ecosystem models (ECOSIM-ECOPATH-ECOSPACE,

bioenergetic/allometric models…)– Dynamic multi-species models or Minimun Realistic Models

(MSVPA, MSFOR, GADGET, MRM…)– Dynamic System Models (OSMOSE, INVITRO, ATLANTIS…)– Extensions of single-species assessment models: ESAM.

• MRM- shared characteristics: – they are system specific;– only a small selected component of the ecosystem is modelled– lower trophic levels and primary production are modelled as

constant or varying stochastically.

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1.2. Introduction: GADGET(www.hafro.is/gadget)

-Globally applicable Area Disaggregated General Ecosystem Toolbox.

- To model marine ecosystems, including both the impact of the interactions between species and the impact of fisheries harvesting the species.

- Three parts:•a parametric model to simulate the ecosystem •statistical functions to compare the model output to data •search algorithms to optimize the model parameters

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1.3. Introduction: Bay of Biscay

• Extends from 48ºN to 43ºN and from 11ºW to the coastlines of France and North-western Spain.

• Biogeographically the region corresponds to a subtropical/boreal transition zone (from Finisterre to Brittany)

• Ecological richness of the region (topographical diversity)

• Why GADGETGADGET?– Two commercially important species in the Bay of Biscay : European hake (Merluccius

merluccius) and European anchovy (Engraulius encrasicolus).– Bay of Biscay is considered a not really rich area concerning to the amount of data available– New literature on ecosystems and diet of target species in the area (Mahe, 2007; Velasco,

2007)– Participation in two relevant European projects BECAUSE(http://www1.uni-hamburg.de/BECAUSE) and

UNCOVER (http://www.uncover.eu) (help from Iceland and Norway).

V IIId

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Lances con bycatch año 2003

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D 9 E 1 E 3 E 5 E 7 E 9 F 1 F 3

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2.1.a. Status of the art: a single-species model for European hake

– HAKE (Northern Stock): main predator in the BoB Merluccius merluccius, Linnaeus 1758

Currently available data (BoB): – W-L relationship from real data– Von Bertalanffy parameters– Survey data: EVHOE (gaps in 1991,1993,1996)– Commercial data: Basque & French (from 1987 to 2003)– Maturity ogives coming from the WGHMM.

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2.1.b. Status of the art: a single-species model for European hake. GADGET-VPA results

•First length-based model in the area which avoids the current assessment problems (i.e. uncertainty on the hake growth pattern)•A total of 35 parameters have been estimated (8 for the initial population, 17 for the recruitment and 10 for the selectivity pattern). Growth parameters have been fixed. •Most recent information for this stock is shown in the last report of the assessment WGHMM (ICES, 2006).• A summary of the most important parameters of this stock is represented in this figure, both from the new model and from the XSA.•Most significant differences in the results of the compared models are shown in the last picture of this figure, the number of recruits. These differences could give us an idea about the recruitment spatial pattern of this species in this area.

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2.1.c. Status of the art: a single-species model for European hake. Predictions (Recovery Plan)

•Predictions (from 2004 to 2015)

•Parameters:

• F´= meanF (last 3years)*constant (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9)

•Reruits = average number of the last three years

•Results:

•SSB upper the precautionary limit always.

•Similar to the WGHMM results

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2.1.d. Status of the art: a single-species model for European hake. New growing pattern

• Testing the new growing pattern given by the sampling experiments carried out during the last years in the area (de Pontual et al., 2006).

• Preliminary results, need to be studied in more detail.

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2.2. Status of the art: a single-species model for anchovy

– ANCHOVY: relevant prey specially for hakes < 30 cm in the BoB (Mahe et al. 2007) Engraulis encrasicolus, Linnaeus 1758

Currently available data (only BoB): – W-L relationship from real data– Von Bertalanffy parameters– Survey data: EVHOE (gaps in 1991,1993,1996), DMPH, PELGAS.– Commercial data: Basque & French ones from ICES WGMHSA (1987

to 2003)

No reasonable results. Working on problems.

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2.3.a Status of the art: preliminary multi-species model (hake eating anchovy)

• Consumption is not dependant neither on predator nor on prey lengths. It has been implemented following a constant suitability function.

• It is well known that this assumption is not realistic as there is a relationship between consumption and size of the preys.

• However, more time is needed to implement this relatioship in the model from the availble data.

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2.3.b Status of the art: preliminary multi-species model (hake eating anchovy). New growing pattern

• Testing the new growing patters (de Pontual et al., 2006)

• Results to study carefully in more detail.

Summary plots

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3. Things to do

• Improve the current models :– fit the anchovy model to the available data in a reasonable way– implement the new data on ecosystem and diet for Hake in this area to

work hard on the multi-species model.– Introduce new target species (preys) as Horse Mackerel (Trachurus

trachurus, Linnaeus 1758), Blue Whiting (Micromesistius poutassou, Risso 1826), Sardine (Sardina pilchardus, Walbaum 1792) and cannibalism effects…

• Introduce new maturation ogives obtained from the recently finished European project RASER.

• Try to extend the model for the whole area covered by the real stock.

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References

• de Pontual, H., Groison, A.L., Pineiro, C. and Bertignac, M., 2006. Evidence of underestimation of European hake growth in the Bay of Biscay, and its relationship with bias in the agreed method of age estimation. ICES J. Mar. Sci., 63:1674-1681.

• ICES, 2006. Report of the Working Group on the Assessment of Southern Shelf Stocks of Hake, Monk and Megrim (WGHMM). ICES CM 2006/ACFM:29:792 pp.

• Mahe, K., Amara, R., Bryckaert, T., Kacher, M., and Brylinski, J. M. 2007. Ontogenetic and spatial variation in the diet of hake (Merluccius merluccius) in the Bay of Biscay and the Celtic Sea. ICES Journal of Marine Science, 64: 1210–1219.

• Plagányi, É. E. 2007. Models for an ecosystem approach to fisheries. FAO Fisheries Technical Paper. No. 477. Rome, FAO. 108 pp.

• Velasco, F., 2007. Alimentación de la merluza europea (Merluccius merluccius L.) en el mar Cantábrico. PhD Thesis.

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