Bay Of Douarnenez Research Articles

An Integrated Biomarker Approach Using Flounder to Improve Chemical Risk Assessments in the Heavily Polluted Seine Estuary.

The objective of this study was to develop an integrative approach in ecotoxicology (from biomarkers to population genetics) to assess the ecological status of fish populations. Flounders (Platichthys flesus) collected after the spawning season in the heavily polluted Seine estuary were compared with the moderately polluted Bay of Douarnenez. The muscle energetic reserves were highly depleted in Seine vs. Douarnenez fish. The Seine fish displaying a reduced capacity to manage the oxidative stress and a higher energetic metabolism. An increase in the content of muscle membrane phospholipids (sphingomyelin, phosphatidylserine, free sterols) was detected in the Seine vs. Douarnenez fish. The data integration allowed to hypothesize relationships between membrane phospholipids, xenobiotic metabolism, bioenergetics, and antioxidant defence. The genetic diversity considering neutral markers was maintained in the heavily polluted Seine population compared with the Douarnenez population. Finally, we suggest that the high physiological cost of tolerance to toxicants in the Seine flounder population could compromise its capacity to respond in the future to an additional stressor like warming waters in shallow depth. Thus, this population could be submitted to an ecological risk.

Vertical distribution of brittle star larvae in two contrasting coastal embayments: implications for larval transport

The ability of marine invertebrate larvae to control their vertical position shapes their dispersal pattern. In species characterized by large variations in population density, like many echinoderm species, larval dispersal may contribute to outbreak and die-off phenomena. A proliferation of the ophiuroid Ophiocomina nigra was observed for several years in western Brittany (France), inducing drastic changes on the benthic communities. We here studied the larval vertical distribution in this species and two co-occurring ophiuroid species, Ophiothrix fragilis and Amphiura filiformis, in two contrasting hydrodynamic environments: stratified in the bay of Douarnenez and well-mixed in the bay of Brest. Larvae were collected at 3 depths during 25 h within each bay. In the bay of Brest, all larvae were evenly distributed in the water column due to the intense vertical mixing. Conversely, in the bay of Douarnenez, a diel vertical migration was observed for O. nigra, with a night ascent of young larvae, and ontogenetic differences. These different patterns in the two bays mediate the effects of tidal currents on larval fluxes. O. fragilis larvae were mainly distributed above the thermocline which may favour larval retention within the bay, while A. filiformis larvae, mostly concentrated near the bottom, were preferentially exported. This study highlighted the complex interactions between coastal hydrodynamics and specific larval traits, e.g. larval morphology, in the control of larval vertical distribution and larval dispersal.

Palaeoenvironmental reconstructions during the Meso- to Neolithic transition (9.2–5.3 cal. ka BP) in Northwestern France: Palynological evidences

Sedimentological, palynological, and micropalaeontological studies carried out throughout the first half of the Holocene, during the Mesolithic/Neolithic transition in the Bay of Brest (i.e. 9200–9000 and 6600–5300 cal. BP) and in the Bay of Douarnenez (i.e. 9200–8400 cal. BP), allowed characterizing coastal environmental changes under the increasing influence of the relative sea-level rise. The gradual flooding of the two studied sites implied a transition from river valleys to oceanic bays as revealed by the gradual retreat of salt marsh environments, as detected through palynological analysis. In addition, these high-resolution studies highlight the regional imprint of the North Atlantic millennial climate variability in north-western coastal environments. Two cold climate events are indeed suggested to have been locally marked by a moisture increase, mainly detected by increases in Lingulodinium machaerophorum, Corylus, and Alnus percentages at 8550 cal. BP in the Bay of Douarnenez and at 6250 cal. BP in the Bay of Brest. Moreover, regarding the Neolithic transition timing in the Bay of Douarnenez, large pollen grains of Poaceae (i.e. Cerealia-type pollen grains) have been detected at around 8600 cal. BP, that is, 1500 years before the general accepted cereal cropping appearance in Western France. These results, consistent with other palynological studies conducted in the French Atlantic coast, could underline a Mesolithic ‘proto-agriculture’ in Brittany.

The WW II German <i>Stützpunkt</i> on the Menez-Hom (Finistère-FR)

The Menez-Hom hill placed between the Brest harbour and the Douarnenez bay, although only about 350 m height, dominates the surrounding territory. Therefore, during the WW II the German Wehrmacht decided to establish on its top a Stützpunkt (support point) for controlling and eventually impeding access to the Crozon peninsula to foreign troops. The available literature gives only fragmentary information about it but the mention of a Gerät (device— radar?) belonging to the FuMB686 Wolga and the presence of rests of a Seetakt radar on the Menez-Hom hill at the end of the war make the location of the Stützpunkt Wolga at the top of the Menez-Hom hill highly probable. The visit of the Stützpunkt site took place on 27/08/2010 and allowed to identify many of its components and to determine its organization.

Trophic niche of two co-occurring ophiuroid species in impacted coastal systems, derived from fatty acid and stable isotope analyses

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 525:127-141 (2015) - DOI: https://doi.org/10.3354/meps11169 Trophic niche of two co-occurring ophiuroid species in impacted coastal systems, derived from fatty acid and stable isotope analyses Aline Blanchet-Aurigny1,*, Stanislas F. Dubois1, Claudie Quéré2, Monique Guillou3, Fabrice Pernet2 1IFREMER, Laboratoire d’Ecologie Benthique, Département Océanographie et Dynamique des Ecosystèmes, Centre de Bretagne, BP70, 29280 Plouzané, France 2IFREMER, Laboratoire de Physiologie Fonctionnelle des Organismes Marins, LEMAR UMR CNRS IRD 6539, Centre de Bretagne, BP70, 29280 Plouzané, France 3Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, LEMAR UMR CNRS IRD 6539, place Nicolas Copernic, 29280 Plouzané, France *Corresponding author: ablanche@ifremer.fr ABSTRACT: The trophic niches of 2 common co-occurring ophiuroids, Ophiocomina nigra and Ophiothrix fragilis (Echinodermata, Ophiuroidea), in 2 contrasting coastal systems of Brittany (France) were investigated. We used a combination of fatty acid biomarkers derived from neutral lipids and stable isotopic compositions to explore the contributions of oceanic versus continental inputs to the ophiuroids’ diet. We investigated 2 different systems with an inshore versus offshore comparison. We sampled potential food sources and surveyed organisms every 2 mo for 1 yr. Spatio-temporal variations in stable isotopes and fatty acid profiles of the ophiuroids were generally low compared to interspecific differences. Fatty acid markers showed that both ophiuroids relied on diatom inputs. However, a more δ15N-enriched isotopic composition as well as a more balanced plant- versus animal-derived fatty acid composition in O. nigra suggest that a broader range of food sources are being used by this species irrespective of location or sampling time. The positive correlation between the 18:1n-9/18:1n-7 fatty acid ratio and δ15N values indicates a higher trophic position for O. nigra (suggesting an omnivorous feeding mode), whereas O. fragilis appears to be more herbivorous. Moreover, the low polyunsaturated/saturated fatty acid ratio associated with elevated bacterial fatty acid markers indicates that O. nigra preferentially consumes detritus, while O. fragilis relies more on fresh phytoplankton-derived material. Both stable isotope and fatty acid analyses suggest that terrestrial inputs do not contribute significantly to the diet of these ophiuroids. However, phytodetritus derived from decomposing green macroalgae contributed to the diet of O. nigra in the Bay of Douarnenez. KEY WORDS: Echinoderm · Feeding ecology · Ophiocomina nigra · Ophiothrix fragilis · Trophic markers · Green algae Full text in pdf format Supplementary material PreviousNextCite this article as: Blanchet-Aurigny A, Dubois SF, Quéré C, Guillou M, Pernet F (2015) Trophic niche of two co-occurring ophiuroid species in impacted coastal systems, derived from fatty acid and stable isotope analyses. Mar Ecol Prog Ser 525:127-141. https://doi.org/10.3354/meps11169 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 525. Online publication date: April 09, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Modelling green macroalgal blooms on the coasts of Brittany, France to enhance water quality management

First recorded in the 1970s, massive green macroalgal blooms have since become an annual recurrence in Brittany, France. Eutrophication (in particular to anthropogenic nitrogen input) has been identified as the main factor controlling Ulva ‘green tide’ events. In this study, we modelled Ulva proliferation using a two-dimensional model by coupling hydrodynamic and biological models (coined ‘MARS-Ulves’) for five sites along the Brittany coastline (La Fresnaye Bay, Saint-Brieuc Bay, Lannion Bay, Guissény Bay and Douarnenez Bay). Calibration of the biological model was mainly based on the seasonal variation of the maximum nitrogen uptake rate (VmaxN) and the half-saturation constant for nitrogen (KN) to reproduce the internal nutrient quotas measured in situ for each site. In each bay, model predictions were in agreement with observed algal coverage converted into biomass. A numerical tracking method was implemented to identify the contribution of the rivers that empty into the study bays, and scenarios of decreases in nitrate concentration in rivers were simulated. Results from numerical nitrogen tracking highlighted the main nitrogen sources of green tides and also showed that each river contributes locally to green tides. In addition, dynamic modelling showed that the nitrate concentrations in rivers must be limited to between 5 and 15mgl−1, depending on the bay, to reduce Ulva biomass by half on the coasts. The three-step methodology developed in this study (analysing total dissolved inorganic nitrogen flux from rivers, tracking nitrogen sources in Ulva and developing scenarios for reducing nitrogen) provides qualitative and quantitative guidelines for stakeholders to define specific nitrogen reduction targets for better environmental management of water quality.

Density fluctuations of the ophiuroids Ophiothrix fragilis and Ophiocomina nigra in the Bay of Douarnenez, Brittany, France

Density fluctuations of the ophiuroids Ophiothrix fragilis and Ophiocomina nigra in the Bay of Douarnenez, Brittany, France

Interval SLAM for underwater robots; a new experiment

This paper provides a new submarine experiment and shows the results of an interval SLAM (Simultaneous Localization And Mapping) method. The SLAM problem is cast into a constraint satisfaction problem where interval propagation algorithms are particularly efficient. The resulting method is applied to the localization of a submarine robot from the GESMA (Groupe d'Etudes Sous-Marines de l'Atlantique), the Daurade during an experiment in the Douarnenez bay, in Brittany (France).

Pre-zygotic factors best explain reproductive isolation between the hybridizing species of brittle-stars Acrocnida brachiata and A. spatulispina (Echinodermata: Ophiuroidea)

The two brittle-stars Acrocnida brachiata (Montagu 1804) and A. spatulispina (Stöhr and Muths in J Mar Biol Assoc, 2009) exhibit strong spatial segregation along the coast of Brittany (France), the first being subtidally distributed relative to the other intertidal species. Despite a very high degree of mitochondrial DNA divergence, previous preliminary results hinted at the potential for hybridization to occur. Therefore, we specifically aim to determine local levels of hybridization between these two species and to investigate the relative roles of pre- and post- zygotic isolation processes acting to decrease local hybridization patterns. Mitochondrial DNA, allozymes and the Internal Transcribed Spacer 2 region of the ribosomal DNA were all used on 529 brittle-stars sampled locally in June and September 2005, among six stations in Douarnenez Bay, a site situated at the tip of Brittany. Only 2.6% of all samples analyzed were identified as potential hybrids. However, these were twice more frequent in June, just after the reproductive period, than in September after selective mortality acted to reduce the proportions of hybrids. In addition to the abrupt bathymetric segregation between the two species, spawning asynchrony also clearly restricts hybridization to low levels, which shows the importance of pre-zygotic mechanisms in maintaining reproductive isolation. Moreover, both limited hybridization events and adult mortalities following reproduction tend to generate local genetic differentiation at the intra-species level. On the contrary, the genetic structure is homogenized by migration of juveniles or adults and hybrids mortalities over the summer period.

In situ growth potential of the subtidal part of green tide forming Ulva spp. stocks

Ulva spp., the algae most responsible for green tides in Brittany (France), are found on the foreshore and in the most beachward wave area (MBWA) of many bays during green tide phenomena. These algae have recently been seen drifting at greater depths (reaching - 20 m). In view of the significant quantities of algae found at these depths, and the less favorable conditions for algal growth than in the intertidal zone, we attempted to determine if they could grow there. For that, during their maximum growth period (from May to July), algae were picked up at three stations located on the foreshore, in the MBWA and in the subtidal (deep) zones of the Bay of Douarnenez, and their nitrogen, carbon and chlorophyll a + b contents were determined, and their photosynthetic activity was compared in the laboratory. The intracellular concentrations did not differ much from one station to another, although in the subtidal zone, the irradiance and the nitrogen concentration in the ambient water were much lower than those measured on the foreshore and in the MBWA. Photosynthetic activity characterized by maximum amounts of oxygen produced at different irradiances and by saturating and compensating irradiance levels, was also quite similar at the three stations. The irradiance, temperature and salinity of the subtidal environment, together with the chemical and photosynthetic characteristics of the algae found in that area, are consistent with the hypothesis that they grow there, and that their nitrogen supply comes from nitrogen releases from sediments. Nevertheless, their growth rate is probably less than that of algae in the MBWA.

Existence of a deep subtidal stock of drifting Ulva in relation to intertidal algal mat developments

Blooms of drifting green algae often develop in shallow coastal zones that receive significant nutrient inputs. Each spring and summer, some fifty bays and coves in Brittany (France) are affected in this way. Until now, in this region, only the algae present in the surf zone or stranded ashore, constituting an intertidal stock, have been taken into account. Another stock of algae, which was subtidal and of the same species ( Ulva spp.), was found in the Bay of Douarnenez, one of the ten areas most affected by these algal blooms. This subtidal Ulva stock was located beyond the surf zone, at depths reaching 15 m. It was about the same size as the intertidal stock, viz., a few thousand tons on average. Subtidal Ulva stocks were generally found lying on the sandy bottom in a distribution showing no particular pattern. Biomass ranged from almost zero to 1.547 kg m −2 of fresh and spun-dried algae. However, at depths from 3 to 7 m they were often arranged in strips a few dm wide, due to the swell's effect. The bottom conditions of temperature, salinity, irradiance and dissolved inorganic nitrogen measured during spring and summer are suitable for the growth of Ulva in the subtidal zone. Both intertidal and subtidal drifting Ulva stocks are mobile and capable of exchanging material. In spring, the intertidal stock's inoculum is likely to come from the subtidal. Later in the season, the subtidal stock could be supplied, at least partially, by the intertidal.

La vallée d'Ys : un paléoréseau hydrographique immergé en baie de Douarnenez (Finistère, France)

L'interprétation de données de sismique réflexion acquises dans la baie de Douarnenez (Finistère) au cours de la campagne Canadou 2000 a permis la restitution de la morphologie du substratum et l'étude des remplissages sédimentaires. Le toit du substratum de la baie de Douarnenez révèle ainsi un réseau de paléovallées, entaillé lors de périodes d'émersion dans un soubassement sédimentaire briovérien et paléozoı̈que. Au cours des derniers interglaciaires, les invasions marines répétées déterminent la répartition des formations sédimentaires du domaine côtier, déposées successivement en conditions continentales, fluvio-estuariennes, puis marines. Pour citer cet article : G. Jouet et al., C. R. Geoscience 335 (2003). Pour citer cet article : G. Jouet et al., C. R. Geoscience 335 (2003). Interpretation of the recent high-resolution survey, CANADOU 2000, in the Bay of Douarnenez (Finistère, France) allowed us to restore the morphology of the substratum and the sedimentary filling of the bay. The Brioverian and Palaeozoic substratum reveals a well-defined network of incised valleys as results of successive emergence stages of the Bay during the Quaternary. Valleys join in a westward-widened mean valley, called Ys Valley. The present-day sedimentary fill of the bay of Douarnenez appears mainly controlled by the Holocene rise and the consecutive highstand. It comprises fluvial and estuarine deposits filling up incised valleys and marine sedimentation extending out of the incised valleys. To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003). To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003).

A new bathyphotometer for bioluminescence measurements on the Armorican continental shelf (northeastern Atlantic)

A new bathyphotometer has been developed by the Oceanographic Laboratory of the French Naval Academy which has performed a series of in situ bioluminescence measurements since 1994. It is used as an additional probe to a Seabird ® CTD. It measures planktonic bioluminescence. It is associated with a SeaTech ® fluorometer. The Armorican shelf has particularly been investigated since July 1994. Results obtained in January and April 1995 off Brittany (France), at the entrance to the Bay of Douarnenez and in the northern Bay of Biscay are presented as examples. A method to separate the bioluminescence background from sharp peaks is presented. The strength of bioluminescence signals was related to seasonal planktonic biomass fluctuations, low in winter, higher in spring.

Variations of fatty acid contents in selected tissues of the female dog cockle ( Glycymeris glycymeris L., Mollusca, Bivalvia) during the annual cycle

The seasonal variations of fatty acid concentrations were studied during two consecutive years in five tissues of female dog cockles ( Glycymeris glycymeris) originating from Douarnenez Bay (South Brittany, France). In all tissues, saturated fatty acids (SFA) were the major forms of fatty acids, followed by polyunsaturated fatty acids (PUFA). The concentrations of monounsaturated fatty acids (MUFA) were low. The C20:0 was most often the predominant SFA in all tissues. The total amount of fatty acids in each of the SFA, MUFA and PUFA series underwent important fluctuations in the foot and in the visceral mass, whereas only slight variations were recorded in the adductor muscles, the tunic coat and the mantle. A main peak of SFA was measured in the foot at the beginning of winter and peak values of SFA were recorded in the visceral mass in April, June and in autumn. The highest concentrations of fatty acids were measured in the visceral mass, in April just before the first and main annual spawning period which occurs in late April or in May, depending of the year. Our results suggest that G. glycymeris feeds both on bacteria-enriched detritic matter and on phytoplankton. Important fluctuations of fatty acids recorded in the visceral mass can, at least in part, be related to certain phases of the reproductive cycle. The foot may constitute a temporary reserve tissue for fatty acids, especially for SFA, at the beginning of winter.

A sampling device for collection and analysis of volatile halocarbons in coastal and oceanic waters

A simple device for collection of sea water samples for measurement of volatile halocarbons has been developed. This device enables collection of samples without contact with the atmosphere and by introducing the sample directly into the analytical circuit eliminates secondary handling of the samples and the risks of contamination associated with it. The device is chemically inert and samples can be stored without contamination for periods of up to 16 h in the case of chlorofluorocarbons (CFCs) and CCl4 and several days in the case of other volatile organic halocarbon compounds before analyses. Standard deviations, as a percentage of the average concentrations measured, varied between 1.4 and 5.7% for a range of halocarbons in coastal waters and were about 2% for CFC-11 and CFC-12 in the oceanic surface waters. Detection limits were less than 0.17 ng l–1 for volatile halocarbons and 0.015 pmol l–1 for CFC-11 and CFC-12. The sampling device has been routinely used for collection of estuarine, coastal and oceanic waters. Results obtained in the coastal waters of Douarnenez Bay and the oceanic waters of the north-east Atlantic are presented as examples.

Arm regeneration in two populations of Acrocnida brachiata (Montagu) (Echinodermata: Ophiuroidea) in Douarnenez Bay, (Brittany: France): An ecological significance

The incidence of arm regeneration in the brittlestar Acrocnida brachiata is assessed for an intertidal and a subtidal population in the Bay of Douarnenez, France. The growth rate of regenerating arm parts in the field and under laboratory conditions and the annual regenerating biomass production complete the study. The frequency of arm regeneration is extensive and comprises nearly 70% of the total arm population in both sampling sites. The position of the breakage points mostly occur in mid-arm level in the tidal flat area and mainly in the distal third part of the arms in the subtidal site. The biomass composed of regenerating tissue is significantly different in both zones accounting for 11.1% (±9.5%) of the total individual biomass in the intertidal area and 6.4% (±8.4%) subtidally. Actively feeding arms appear to be the least damaged. To maximize fitness, the intertidal individuals of Acrocnida brachiata seem to allocate energy to arm regeneration at the expense of somatic growth. Highest arm growth per individual was recorded in the field and comprises 1.2 mm·day −1 for individuals with two amputated arms. Subtidally, the annual production invested in regenerating tissue is 33 g dry wt·m −2 (19 g AFDW·m −2).

Three New Species of the Genus Alexandrium (Dinoflagellata)

Three new species of the dinoflagellate genus Alexandrium are described. Alexandrium tamiyavanichi is in the subgenus Alexandrium in which the Po and 1' are connected. This species is closely related to A. cohorticula, but it differs by its general shape, the Po and 1', the shape of its left sulcal list, and some sulcal plates. The other two species belong in the subgenus Gessnerium in which the Po and 1' are completely disconnected. Alexandrium taylori has a pentagonal 1' and a ventral pore. It differs from the closely related species A. pseudogoniaulax (Biecheler) by the shape of 1', the position of the ventral pore, and all of the sulcal plates. Alexandrium margalefi is the only species of this genus described to date with a quadrangular 1'; it also has a ventral pore. Of the three species, only A. tamiyavanichi is known to produce paralyzing shellfish poisoning For the past several years, I have worked on a revision of the dinoflagellate genus Alexandrium Halim, 1960, which is of great practical importance because several of its members are associated with human poisoning caused by ingestion of toxic seafood. This taxonomic revision, which is in final preparation, is based on examination of numerous specimens collected world-wide from most of the geographic locations from which members of the genus have been recorded. However, to provide more immediate knowledge of three new species, descriptions are presented earlier here. MATERIALS AND METHODS Material for Alexandrium tamiyavanichi came from a culture initiated from a specimen obtained at Ang Sila in the Gulf of Thailand. Material for Alexandrium taylori came from a plankton sample collected in the bay of Arcachon, France. Specimens of A. margalefi came from plankton samples and from cultures, both from Vigo, Spain. Specimens of each of the three species were isolated, drawn, and measured. Many thecae were dissociated with the aid of sodium hypochlorite, which destroyed the protoplasm and separated the plates so that they were distinguishable. Plates were studied with a light microscope using bright-field oil immersion and phase-contrast objectives. ' I thank Dr. T. Piyakarnchana and Miss Sucharno for the material from Thailand, Dr. P. Lassus for the samples from Arcachon and the Bay of Douarnenez, France, and Drs. J. Blanco and S. Fraga for the plankton samples and cultures from Vigo, Spain. I specially thank Dr. K. A. Steidinger and Miss B. S. Roberts for suggestions, criticisms, and help with the manuscript. TRANS. AM. MICROSC. SOC., 113(2): 216-220. 1994. ? Copyright, 1994, by the American Microscopical Society, Inc. This content downloaded from 207.46.13.16 on Thu, 16 Jun 2016 06:13:47 UTC All use subject to http://about.jstor.org/terms VOL. 113, NO. 2, APRIL 1994

Seasonal Variation of Copper, Nickel and Lead in Western Brittany Coastal Waters (France)

Seasonal variation of copper, nickel and lead were studied in the Douarnenez Bay and the Iroise Sea during April 1983-February 1984 period. Our results compare favourably with those found in neighbouring coastal areas (1·5 nmol 1-1 <Cu <8·0 nmol l-1; 1·4 nmol l-1 <Ni <6·8 nmol l-1; and 0·07 nmol l-1 <Pb < 2·70 nmol l-1).Analyses of metal-salinity and metal-nutrient (nitrate and silicon) relationships, according to different hydrological patterns, show clearly that both the concentration and distribution of Cu, Ni and Pb are significantly influenced by seasonal changes. The main factors which control the cycle of the metal are: (a) the mixing of fresh and saline water, (b) the phytoplankton development and (c) the establishment of the frontal structures.

Environmental Instability and Demographic Variability in Acrocnida brachiata (Echinodermata: Ophiuroidea) in Douarnenez Bay (Brittany: France)

Abstract. The recruitment and growth modalities of two populations of Acrocnida brachiata (Echinodermata: Ophiuroidea) from the intertidal and from a depth of 20 m in Douarnenez Bay (Brittany) were compared. This study was conducted in order to establish whether the populations developed differently according to environmental stability. The results were compared with those found in another amphiurid, Amphiura filiformis, distributed along a similar gradient of disturbance in the subtidal zone. The purpose was to determine whether the biological parameters from different species vary in a similar manner along such a gradient and. if not, what is the role of biotic and physical factors in the control of demographic structure in intertidal and subtidal populations.

Comparative study of growth of flatfishes on the west coast of Brittany

Lusitanian and boreal flatfish species live in the Bay of Douarnenez (Brittany, France); ten are abundant enough to be the subject of this growth investigation. In all species, females attain greater ultimate size than males, and oldest specimens are frequently female. Species are segre‐gated to their longevity: those rapidly reaching their asymptotic length have the shortest life spans and also the highest values of the Von Bertalanffy parameter K.In the bay, species of the boreal fish fauna (plaice, dab) find suitable environmental conditions for rapid growth; fish of the Lusitanian fauna (sand soles) grow slower than those living in southern areas.In the Atlantic Ocean, the growth of the sole is better than in the North Sea and the Mediterranean.