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The English Channel/La Manche contains a number of multi-species multi-gear fisheries. These fisheries are exploited by UK, French and Belgian fishers. The objective of this project is to develop a bioeconomic model of the fishery than encapsulates the key economic, biological and technical interactions in the fishery. This model, when finalised, may be use to examine the potential effects of fisheries management policies on both the financial and economic status of the fishers as well as the biological status of the resource.
Biological component
The key species in the Channel were classified into three main categories (Table 1). The first category are species for which data are considered adequate to develop age structured dynamic models. The second group of species are those where the data is adequate for the development of dynamic models, but these are likely to be simpler models (e.g. surplus yield models). The third category includes those species where there is insufficient data to develop dynamic models, but are sufficiently important (economically) to keep in the model as separate species. All other species will be aggregated into general categories (e.g. other crustaceans etc.).
TABLE 1. CLASSIFICATION OF SPECIES FOR WHICH DATA IS AVAILABLE
N° Dynamic Modelling ICES assessed species Modelling possible(Data rich) Simple stochastic model (ad-hoc)
cod edible conger eel
hake crab crawfish
mackerel pollack john dory
herring scallops lobster
monkfish spider lemon
plaice crab sole
sole turbot ling
whiting brill megrim
bass pout cuttlefish
dab
spurdog
gurnard
red mullet
queens
black bream
skates and rays
squid
To date, only limited analyses have been undertaken. Initial use of length and age based assessment techniques on UK data for turbot, brill and black bream (data-rich/ad-hoc species), john dory and red mullet (ad hoc species) produced varying results. Age based equilibrium cohort analysis models for turbot and brill (mean data 1994-1995) showed F increasing with age and reaching a maximum of 0.55 at age 7, and 1.2 at age 9 respectively (with M at 0.2 and starting F of 0.8).
For black bream maximum F was 0.87 at age 7, with M at 0.2 and starting F at 0.8. Length based methods calculated from aggregated length data for john dory gave a consistently high estimate of Z (around 1.5: with M at 0.2 F is therefore 1.3) but this may be biased by a migration out of the Channel by older fish. Similar methods applied to red mullet also gave relatively high Z and F, but in this case the Channel is supposed to support a coherent stock, and the methods would therefore suggest a high exploitation rate on this species. Attempts at estimating the stock dynamics of cuttlefish have also been undertaken (Dunn [no date]).
Initial trials with production models (Fox and Schaefer fitted using log-normal or gamma error models) on the turbot, brill and black bream stocks using data for 1986-1996 all give relatively poor fit (r2<0.5). Similar trials on the western Channel sole stock have given a better fit (r2>0.9) and show that, with an initial stock level of 0.2-0.4 the fitted model estimates a current biomass that approximates well with the ICES assessment (data used was for 1972-1995). The failure of the production models with turbot, brill and black bream may be largely due to the short time series of data used, with less variation in total catch and effort levels, or because of the less reliable recording of landings and effort of these non-quota species (i.e. poorer data quality), or because of a general failure of the model.
These initial assessments were carried out using UK data, and may be improved when the international data are available. The suitability of techniques for particular species is the subject of further discussion and study, but the current work would tend to suggest that as many methods as possible should be used on non-ICES assessed species to obtain the best assessment.
Economic components
An economic survey of UK fishers (Pascoe, Robinson and Coglan 1997) suggested that the fishery was not earning economic profits in 1994-95. Small boat owners, however, appeared to be performing relatively better than the larger boats. Further analysis of the survey data suggested that much of the economic profits that were being generated were intra-marginal rents, and that the level of resource rent in the fishery was most likely negative (Coglan and Pascoe [no date]).
A survey of French fishers produced similar results (Boncoeur, Bailly and Le Floc'h 1996). Economic surveys of fishers in both countries are being undertaken as part of the bioeconomic modelling project. The data from these surveys will be used in the model.
An analysis of price-quantity relationships is also being undertaken. Analyses of the key high valued species in the UK suggest that prices are generally inflexible with respect to the quantity landed (Jaffry, Pascoe and Robinson 1997). This analyses was limited to the four highest priced species landed in the Channel on the UK market (lobster, turbot, bass and sole). Similar analyses are being undertaken for the other key species, both in the UK and France. These relationships will be incorporated directly into the model when finalised.
The factors affecting the allocation of effort by fishers is also an important consideration. A study of fisher motivation suggested that fishers in the Channel operated in a manner consistent with profit maximisation (Robinson and Pascoe 1997).
DISCUSSION
The project is still in a fairly early stage. However, the project team has managed to develop a comprehensive information base on the fishery. This information base will prove invaluable when developing and validating the model. It is expected that a number of models will be developed during the course of the study. These models will focus on particular aspects of the fishery. For example, it is expected that the project team will develop a short run model, a dynamic model and long run equilibrium model. These models will be able to address different sets of management questions. The development of such a comprehensive set of models will allow more effective management of the fishery in the future. This will be of benefit to the industry as well as the fish stocks.
REFERENCES
Boncoeur J., Bailly D. and Le Floc'h P., 1996. Enquete economique sur la peche cotiere professionnelle en Bretagne-Nord et dans le Golfe Normand-Breton. Programme AMURE, Universite de Bretagne Occidentale, CEDEM (126 p.).
Coglan, L. and Pascoe, S. (no date). Resource rents, intra-marginal rents and fisheries management performance indicators, submitted to Agricultural and Resource Economics Review.
Dunn, M. R. (no date). Aspects of the stock dynamics and exploitation of cuttlefish, Sepia officinalis (Linnaeus 1758), in the English Channel, submitted to Fisheries Research.
Jaffry, S., Pascoe, S. and Robinson C. 1997, Long run price flexibilities for high valued species on the UK market, paper presented at the IXth annual conference of the European Association of Fisheries Economists, Quimper, 28-30 April. (also submitted to Applied Economics).
Meuriot E., Cochet Y., Fifas S., Foucher E. and Gates J., 1987. Licences de peche et gestion d'une pecherie: analyse bioeconomique de la gestion de la peche a la coquille Saint-Jacques en baie de Saint-Brieuc. Brest, IFREMER (Rapports economiques et juridiques, n°4).
Pascoe, S. 1995, Modelling the UK demersal trawl component of the English Channel, Paper presented at the 5th EAFE Bioeconomic Modelling Workshop, Edinburgh, 24-27 October 1995.
Pascoe, S. 1997, A preliminary bioeconomic model of the UK component of the fisheries of the English Channel, CEMARE Research Paper, CEMARE.
Pascoe, S. Robinson, C. and Coglan, L. 1997, Economic and Financial Performance of the UK English Channel Fishery, CEMARE Report No. 44, University of Portsmouth.
Robinson, C. and Pascoe, S. 1997, Fisher behaviour: Exploring the validity of the profit maximising assumption. paper presented at the IX th annual conference of the European Association of Fisheries Economists, Quimper, 28-30 April.
Santarelli, L and Gros, P., 1984. Towards an optimal management of resources in the whelk fishery (Buccinum undatum) of Granville. Lessons from a bioeconomic model. Rev. Trav. ISTPM48 n°1-2, pp. 23-33.
Tetard A., Boon M. et al., 1995. Catalogue international des activites des flottilles de la Manche, approche des interactions techniques. Brest, IFREMER, 337 p.
Ulrich, C., Gascuel, D., and Pascoe, S. 1997., 'English Channel Fisheries: a complex multifleet-multispecies dynamic to be modelled', Poster presented at the 1997 ICES meeting, Baltimore, ICES CM 1997/HH:15 (Poster)
INTRODUCTION
The English Channel (ICES sub-regions VIId and VIIe) contains a number of multi-species multi-gear fisheries. These fisheries are dominated by sole, plaice and high value shellfish species such as lobster and scallops. Commercial activity in the fisheries is predominantly undertaken by fishers from the UK and France, although vessels from other EU countries (such as Belgium) and the Channel Islands are also active in the fisheries. In total some 4000 boats operate within the English Channel, over half of which are UK boats. About 90 per cent of these boats operate within 10 km of the coast (Tetard, Boon et al. 1995).
The overall objective of the project is to develop a bioeconomic model of the English Channel/La Manche fisheries that can be used as an input into management decision making. The model will be used to estimate how changes in management will affect the economic status of fishers, and to estimate how management policies will affect exploitation rates on resource populations, the effect on stock biomass and the resultant short and long term yields in the fishery. In this paper, the work to date on the project will be briefly reviewed.
PREVIOUS STUDIES
Pascoe (1995) developed a preliminary bioeconomic model of the trawl component of the fishery. This model encompassed five metiers - two otter trawl metiers and three beam trawl metiers. This model was further expanded to include static gear metiers (pots, lines and nets) as well as dredging metiers (Pascoe 1997). However, no stock dynamics were included in the model so the usefulness of the model was limited to short term analyses.
A number of bioeconomic studies have also been conducted on the French side of the fishery. Santarelli and Gros (1984) developed a bioeconomic model of the whelk fishery in the western Channel. The model was used to estimate the fleet size and number of pots per boat that maximised profits in the fishery. Meuriot et al (1987) developed a bioeconomic model to examine the scallop fishery in the bay of Saint-Brieuc.
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