Laurent Le Grel

Price-Cost Margins and Structural Change: Sub-Contracting within the Salmon Marketing Chain

Some recent studies have benefited from advances in time series econometrics in order to evaluate price transmission mechanisms along the marketing chain. Due to the length of time series, structural changes may affect the evaluation of price-cost margins. In the case of the fresh salmon trade between Norway and France, the gross margin between producers and retailers has changed in level between January 1988 and December 1999. This article accurately identifies the date of a structural change using a range of recent ADF testing procedures (Gregory-Hansen tests, forward and backward recursive tests), before looking for the causes of the change through a survey. Two major factors can be identified: the product form and the marketing channel. Interestingly, both the increasing level of processing and the development of supermarket chains have resulted in a new role for the intermediaries, shifting from mere commercial intermediation to sub-contracting for the big retailers. Copyright Blackwell Publishing Ltd 2005.

OYSTER FARMING AND EXTERNALITIES: THE EXPERIENCE OF THE BAY OF BOURGNEUF

The history of the French shellfish industry is marked by a series of overfishing crises occurring in most of the open-access shellfish beds. When the concession system was introduced (1852), it was designed to cope with congestion and overfishing issues more than with the development of shellfish culture. After closing the production cycle in the late 19th century, the oyster industry kept suffering major crises such as massive disease outbreaks. Their occurrence can be analyzed in terms of overexploitation resulting from environmental externalities. We will show that this can create a backward-bending supply curve for oysters, using the Bay of Bourgneuf as a case study. In this bay, 400 firms, mostly family-sized, are being conceded 1,000 ha and sell 10,000 tons of Crassostrea gigas oysters a year. The paper presents a typology of farmers based on a survey that shows that farmer behavior can be aggregated into three main groups.

MODELING OYSTER FARMING ACTIVITIES IN COASTAL AREAS: A GENERIC FRAMEWORK AND PRELIMINARY APPLICATION TO A CASE STUDY

We present an approach for modeling oyster farming activities under spatio-temporal constraints. Combining an object-oriented geodatabase, a geographic information system and a multi-agent model, the methodology developed here offers a formal framework for analyzing the variability of the conditions in which activities are conducted and for evaluating how production systems adapt to this variability. A prototype specific to the Bay of Bourgneuf (France) was developed to study the spatio-temporal variability of oyster growth according to the quality of coastal waters and the oyster production strategy.