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Case study 8, Base case BC2: Evaluation of the current exploitation pattern to different fleets of different coutries harvesting the same species in the same area by assumming recruitment independent of stock size (Gulf of Lions).


This case study scenarion includes a 15-year catch projection of the fishery assumming no changes in the current exploitation pattern

Description of the fishery, stocks and management system

See general introduction of CS8

Description of the base case and scenario evaluations

See general introduction of CS8

Data and parameters

Stock data

The assessment of the current hake population in the Northen Alboran Sea was obtained by using a surplus production model (Polaeck et al. 1993).

Fleet data

We worked at vessel level. Data on catch by species by fleet and by vessel was available since year 2000. Several inputs were used in a Cobb-Douglas production function: engine power, effort. Vessels' characteristics, social data and profitability of the fishery was used in a behavioural model.


FLR (Operating Model)

The FLR packages are still being developed. Currently most estimations have been developed in gams or matlab.

Conditioning of Operating Model

Fisheries & Fleets

The data consists of two different fleet segments. Both of them are trawlers. One of them consists small and not very powerful vessels and operate in areas close to the coast. The second fleet is composed of bigger and more powerful vessels and operate further from the coast. There are only 5 vessels that catch hake with lines. They have not been considered in the analysis.


We have economic data regarding prices per boat and time period. Variable costs have been included like ice, fuel, crew costs and taxes. We have also considered fixed costs such as maintenance, investments made to the vessels, amortizations and economic depreciation.

Management Procedure

The stock is managed through technical measures and effort control rules, thus there is no specific management procedure (e.g. harvest control rules, TAC, quotas)


Results indicated a stable production pattern with annual catches being in the range (prob > 50%) of 2900-3200 MT throughout the 15-year projection period. Variability in the predicted catches slightly increased as progressed through the years. Individual fleets also exhibited a relatively constant production, although some of them (e.g. trawlers) more variable than the others. This was probably due to the largest share of the catches corresponding to these fleets. The catches ranged between: a) Spanish trawlers: 320-340 MT (prob > 50%), b) Spanish long-liners: 140-150 MT (prob > 50%) c) French trawlers: 1900-2100 MT (prob > 50%) d) French gillnets: 540-580 MT (prob > 50%).

Figure 1. Projected Box-whisker plots by year, for the production estimates obtained from 1000 simulations.


Maravelias, C. D. & C. Papaconstantinou 2006. Geographic, seasonal and bathymetric distribu-tion of demersal fish species in the eastern Mediterranean. Journal of Applied Ichthy-ology 22: 35-42.


Aldebert, Y. & C. Carries. 1988. Problèmes dans l’exploitation du merlu en Golfe du Lion. Rapport 5ème Consultation Technique du Conseil Général des Pêches de la Méditerranée. FAO Fish. Rep., 395: 87-91.

Aldebert, Y., L. Recasens & J. Lleonart. 1993. Analysis of gear interactions in a hake fishery: The case of the Gulf of Lions (NW Mediterranean). Sci. Mar. 57(2-3): 207-217.

Aldebert, Y. & L. Recasens. 1996. Comparison of methods for stock assessment of European hake, Merluccius merluccius, in the Gulf of Lions (north-western Mediterranean). Aquat. Living Res. 9(1); 13-22.

Cheret, Y., H. Farrugio, A. Jadaud, P. Lespagnol, C. Mellon, M. Gaza, E. Massutí, G. Pomar, P. Pereda & J. Lleonart. 2002. Stock assessment of the French-Spanish shared stock of hake (Merluccius merluccius) in the Gulf of Lions. Working document Nº 6 to the GFCM SAC Working group on the assessment of demer-sal stocks, Rome 20-22 March 2002.

Fiorentino, F., A. Zamboni & G. Relini. 1998. La selettività della rete a strascico in Merluccius merluccius sulla base delle esperienze riportate in letteratura. Biol. Mar. Med. 5(2): 465-474.

Lleonart, J. & J. Salat. 1992. VIT: Software for fishery analysis. FAO, Computerized In-formation Series – Fisheries, Nº 11. Rome.

Lleonart, J., F. Maynou, L. Recasens & R. Franquesa. 2003. A bioeconomic model for Mediterranean Fisheries, the hake off Catalonia (Western Mediterranean) as a case study. Sci. Mar., 67 (suppl. 1): 337-351. In: Fisheries stock assessments and predictions: Integrating relevant knowledge, Ø. Ulltang, G. Blom [eds.].

Oliver, P. & E. Massutí. 1995. Biology and fisheries of western Mediterranean hake (M. merluccius). In Hake: Biology, fisheries and markets. Alheit, J. & T. J. Pitcher (ed.) London: Chapman & Hall, pp. 181-202.

Maravelias, C. D. & C. Papaconstantinou 2006. Geographic, seasonal and bathymetric distribu-tion of demersal fish species in the eastern Mediterranean. Journal of Applied Ichthy-ology 22: 35-42.

Papaconstantinou C. & K.I. Stergiou. 1995. Biology and Fisheries of Eastern Mediter-ranean hake (M. merluccius). In: Hake: Biology, fisheries and markets. Edited by J.Alheit and T. Pitcher. Chapman & Hall, London, 1995.


EFIMAS Contribution to the work

This work has been performed under the EFIMAS Project.


Costas Papaconstantinou (HCMR),

John Haralabous (HCMR),

Christos Maravelias (HCMR),

George Tserpes (HCMR),

Vincenzo Placenti IREPA (Italy)

Ramon Franquesa UB (Spain)

Jordi Guillen UB (Spain)

Ines Herrero UPO (Spain)

Ikerne del Valle UPV (Spain)

Kepa Astorkiza UPV (Spain)

Inma Astorkiza UPV (Spain)

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