| Abstract |
This report has been achieved during a work as short-term consultant in Chesapeake Biological Laboratory (University of Maryland) in the Laboratory of Prof. B. J. Rothschild, for a period from July 7 to August 7 1989 and at Ifremer Laboratory of La Tremblade. The terms of reference of the consultance were : to compare the oyster fishery researches between the Chesapeake Bay and Europe, particularly in reference to the French coast. To evaluate the on-going Chesapeake Bay oyster stock assessment project and to provide its comments and recommendations. To work on spat settlement in the Bay. This study was funded by the National Oceanic and Atmospheric Administration, by the Maryland Department of Natural Resources under contract F 1666-89-008 and by the Institut Français de Recherche pour l'Exploitation de la Mer. To compare the oyster production in France and in Maryloand and their respective problems, two articles have been wrotten : the first one "oyster culture in European contries" describe the caracteristics of oyster culture with the biology of the cultivated species, the salinity and temperature tolerance, the sexual development and spawning, the larval development, the growth, the history of the fishery, the methods of culture of harvesting and the uses and processing. The main constraints are analysed like diseases, parasites, predators competitors, pollution and toxic phytoplanctonic blooms. The european and mainly French axe of researches are presented for the technics of culture, the pathology, the carrying capactity of environment for cultivation of molluscs and the genetic programms. This paper asked by Dr W. Menzel have been wrotten to be published in CRC Press as a chapter of the book "Estuarine and marine bivalve mollusc culture". The second one "Decrease of the oyster production in the Maryland portion of the Chesapeake Bay : causes and perspectives describe the reconstitution of the historical landings of oyster showing three levels of exploitations of the Bay. The responsaiblity of the overfishing and the use of the different gears is presented concurently with the decrease of the surface of the habitat mainly due to the siltation and anoxic waters. The impact of the deseases joined to the predation are presented. Alternative strategies for restoration of oyster production in the Chesapeake Bay are evaluated to allow an increase of the oyster fishery. This report consigned with B. J. Rotschild and P. Goulletquer will be presented at the next ICES statuory meeting and published in an international review of fisheries. The evalution of the on-going Chesapeake Bay oyster stock assessment project have been achieved during the stay in Maryland. The recommandations have been given during different meetings particularly on : the technics for estimation of the biais of the different gears for sampling oysters. The problem of estimations of the oyster stock relevant with the absence of knowledge of the surface of the oyster bars, joined to the problem to keep or not the points where the biomass is zero and the consequences on the overestimation of the stock. The comparisons for the growth and survival rate between the experimental culture in suspension with on oyster bed on the bottom located in the vicinity. The control of the occurence of fixation of spat in the water column on shells in suspension. |
