Bay Of Douarnenez Research Articles

Population structure of thornback rays Raja clavata and their movements in the Bay of Douarnenez

The population structure of the thornback ray, Raja clavata L., expressed in terms of length and sex, seems to be related to hydrological conditions prevailing on the sampling areas. In the exposed area (Cove of Bertheaume), females are more frequently captured than males, and indeed represent the entire catch in the summer. In contrast, in the relatively sheltered area (Bay of Douarnenez) a majority of adult males and immature females are caught.After winter, only adults and juveniles of Raja clavata migrate into the Bay of Douarnenez. This bay may be a mating area for adults and also a nursery for juveniles particularly for immature females.

Catches and geographical distribution of selachians on the western coast of Brittany

In this study the selachians were captured monthly on inshore grounds (10–30 m deep) with a beam-trawl over ten years (1975–1984), mainly in the Bay of Douarnenez, the Roads of Brest and the Bertheaume Cove area (west Brittany). Catches were composed of five species, accounting numerically for 6–5% of the mean catch of the trawled fishes, but reached up to 20% in Bertheaume Cove. On account of the adaptability to different bottom substrates Raja clavata is the most common species. Raja microocellata is uncommon except in the Cove of Bertheaume where it represented half of the selachian biomass captured.

Variations in the reproductive cycle of Acrocnida brachiata (Echinodermata: Ophiuroidea) according to environment in the Bay of Douarnenez (Brittany)

The annual reproductive and somatic cycles of the brittlestar Acrocnida brachiata are described using gonad and gut indices for intertidal and subtidal populations in the Bay of Douarnenez, France. Oocyte size frequency diagrams complement the gonad study in the subtidal population. Clearly marked reproductive cycles are defined in both populations. Accelerated gonad growth takes place in spring and the gonads reach the peak of development in May-June each year. Spawning is completed by the end of August. Oocytes reach a mean diameter of 150 μm and a new generation of oocytes appaears in the ovaries during the spawning period. The gut indices show a clear inverse relationship with the gonad indices in the intertidal population, but this relation is not well revealed in the subtidal population.

The reproductive biology and the pathological changes of the plaice Pleuronectes platessa (L.) after the ‘Amoco Cadiz’ oil spill along the north-west coast of Brittany

The reproduction of the plaice has been studied in the North Sea (Wimpenny, 1949; Barr, 1963), in the eastern and western English Channel (Houghton & Harding, 1976) as well as in the bay of Douarnenez (Deniel, 1981). In 1972, Lahaye described the sexual cycle of the plaice caught in the Portsall area.After the wreck of the ‘Amoco Cadiz’ off Brittany in March 1978, more diversified studies of this species were made to assess the effects of the oil spill on the plaice stocks in the contaminated area. In Lannion and Morlaix Bays, these fishes exhibited a clear decrease of growth, fin necrosis and an absence of recruitment in the population in 1978 (Desaunay, 1981; Maurin, 1984). In the Abers Wrac'h and Benoit, estuaries of the north-west coast of Brittany (Fig. 1) which were gravely affected by the oil spill, Haensly & Neff (1979) and Miossec (1981, 1984) noted a big change in reproduction. Conan & Friha (1981) observed abnormally low growth for plaice in Aber Benoit.

Some Observations on the Biology and the Ecology of a Venus Striatula Population in the Bay of Douarnenez, Brittany

INTRODUCTIONVenus striatula (da Costa) (= Venus gallina L.) occurs in high densities in shallow water on a bottom of clean fine sand in the Bay of Douarnenez. The environmental conditions are characterized by an obvious sediment instability due to a high exposure to westerly swells (Guillou & Le Moal, 1978). This species is preferentially distributed in the fine sands (Petersen, 1913; Thorson, 1957), but is relatively tolerant towards certain ecological factors and so is sometimes found in very muddy sediments. It also shows an extended latitudinal range, since it is recorded from the Lofoten Islands to the Canaries, in the Mediterranean and the Black Sea (Tebble, 1966).