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Données récentes sur les caractéristiques morphologiques et biologiques de la population d'Alose feinte du Rhône (Alosa fallax rhodanensis Roule, 1924)
Abstract
Les caractéristiques morphologiques et biologiques de la population actuelle d'Alose feinte du Rhône (Alosa fallax rhodanensis) sont présentées. Elles sont analysées à partir d'un lot de 1479 adultes capturés (pêche au filet) lors de leur migration anadrome au cours de trois années. Les critères morphologiques utilisés (notamment le nombre de branchiospines) et leur faible variabilité individuelle ne font apparaître qu'un seul taxon, identifié comme étant celui d'Alosa fallax rhodanensis. La longueur moyenne (Lf) est de 433 mm pour un poids moyen de 1115 g; avec un spectre d'âge s'étalant de 3 à 8 ans. Le rapport des sexes est en moyenne en faveur des femelles (mâles/femelles = 0,61). Celles-ci ont un âge moyen de remontée (AMR) plus élevé (5,24 ans) que celui des mâles (4,21 ans). A âge égal, les femelles montrent une plus forte croissance linéaire et pondérale que les mâles. L'âge moyen de première reproduction (AMPR) est plus faible que l'AMR et montre un phénomène d'itéroparité important ; il est plus élevé chez les femelles (4,00 ans) que chez les mâles (3,35 ans). Le nombre de reproductions antérieures varie de 1 à 5 et le pourcentage de poissons s'étant déjà reproduits au moins une fois est en moyenne de 48,6 %, mais est plus élevé chez les femelles. Il existe des différences inter-annuelles significatives pour la plupart des paramètres biologiques. Les résultats obtenus sont discutés et comparés à ceux de DOUCHEMENT (1981) en prenant en compte la part occupée par les méthodes d'échantillonnage dans la variabilité. D'une part, ils confirment certaines caractéristiques biologiques du genre Alosa et du taxon étudié et, d'autre part, ils suggèrent un possible changement de la stratégie démographique de l'Alose du Rhône en 20 ans.
... Cependant, dans un affluent de ce dernier fleuve (rivière Zézère), elle est trouvée sous une forme lacustre (non amphihaline) suite à la création d'un barrage (Castelo de Bode) à son embouchure avec le Tage, il y a une quarantaine d'années (ALEXANDRINO, 1996). Enfin, la grande alose, considérée comme rare sur la façade méditerranéenne française (ROULE, 1924) mais introduite dans le Rhône à partir de la Dordogne dans le milieu de ce siècle (HOESTLANDT, 1958) paraît avoir totalement disparu de ce fleuve aujourd'hui (LE CORRE et al., 1997). ...
... On the French side of the Mediterranean allis shad is considered rare (ROULE, 1924). It seems to have completely disappeared from the Rhône (LE CORRE et al., 1997) in to which it was introduced via the Dordogne river in the middle of the twentieth century (HOESTLANDT, 1958). ...
... The date can vary from the 1 st May for the Moroccan Alosa (SABATIÉ, 1996) to the 15 th May for allis shad of the Lima (SABATIÉ et al., 1996) to the 1 st July for allis shad in France (CASSOU-LEINS and CASSOU-LEINS, 1981;DAUTREY and LARTIGUE, 1983;MENNESSON-BOISNEAU et al., 1986;TAVERNY, 1991). The median date for twaite shad can range between 1 st June for the populations from the Rhône (LE CORRE et al., 1997) and Severn (APRAHAMIAN, 1982) to 1 st July for the Loire (MENNESSON-BOISNEAU and BOISNEAU, 1990). Because of these differences, no universal anniversary date can be used, only the anniversary date of the population being studied, if it is known. ...
The general objective of this guide is to provide a practical manual for interpreting scales and the estimation of age of Alosa from the East Atlantic and West-Mediterranean (Allis shad, Atlantic and mediterranean shad). Following a brief presentation of the species, populations and rivers studied, the scales, sampling methods and their preparation for reading are described in detail. Definitions and a standard system of notating age are given. The majority of the difficulties encountered in the interpretation of scales are analysed, solutions proposed and some recommendations given. The whole guide is largely illustrative using examples of typical and atypical scales from the various taxons of the different populations studied.
... sur l'Ardèche à Saint Just. L'alose feinte du Rhône (Alosa fallax rhodanensis), espèce grande migratrice est répertoriée sur cette rivière qui comporte des zones de fraie (Le Corre et al. 1997) mais est rarement capturée : uniquement en 2011 et 2012 sur une période allant de 1998 à 2014, et à hauteur d'un seul spécimen). Dans notre étude, l'espèce a été détectée dans dix des 11 filtrations, ce qui démontre l'intérêt de l'approche ADNe pour le suivi des espèces rares. ...
... Une cause similaire est envisagée sur l'Ardèche mais reste à démontrer La présence d'Alosa spp. sur l'Ardèche à Saint-Just est tout à fait cohérente avec les connaissances sur Alosa fallax espèce grande migratrice dont les frayères sont régulièrement observées sur ce cours d'eau (Le Corre et al. 1997). Mais cette espèce est rarement capturée dans les pêches électriques de suivi (uniquement en 2011 et 2012 sur une chronique allant de 1998 à 2014), et le cas échéant en très faible abondance (un seul exemplaire). ...
In recent years, environmental DNA (eDNA) has drawn much attention due of its high
potential for the study of biodiversity and its low cost compared to traditional
sampling. In particular, eDNA metabarcoding (or multi-specific approach) allows the
detection of a set of taxonomically related species (Teleostei, amphibians ...).
However, the nature and properties of eDNA remain poorly known (production, lifetime,
transport). The aims of this PhD work were to participate at the implementation of
a new eDNA metabarcoding pipeline analysis (i.e. from sampling analytical processes
to bioinformatics analyses) and to assess the spatiotemporal representation of the
eDNA signal for the description of fish communities. It was conducted in partnership
between IRSTEA-SPYGEN-CNRS-ONEMA and in collaboration with EDF R & D and
CEN-RA.
First, this document presents the different stages of validation (in silico, in vitro and in
situ) of the Valentini et al. (2016) pipeline as well as the validation of the teleostei
metabarcode, particularly in situ (filtration of about 45 L of water). The current status of
the reference database is described (identified taxa and taxonomic levels of detection).
The ecological representativeness of the pipeline in running waters was evaluated in
comparison with electrofishing inventories that were performed simultaneously. The
number of fish species detected by eDNA metabarcoding was well above that
obtained using electrofishing (approximately 50% additional species). Previous records
on the sampling sites (review of more than 10 years of electrofishing) show that the
additional species detected using eDNA had already been identified on the site. An
experiment on a lake-river gradient provided initial results regarding the eDNA
detection distance (Civade et al., accepted). The lake species are detected in the outlet
stream at a maximum of two kilometres from the lake. In addition, eDNA can clearly
separate fish assemblages that are few kilometres apart. In a lake environment, a more
substantial sampling seems necessary. Finally, preliminary results show that, on several
sites, there is a significant relationship between eDNA signal intensity (number of
reads) and relative abundances of species.
Third, different eDNA sampling strategies (ponctual or integrated sampling) have
been tested on large rivers. The results show no significant differences. The analysis of
sampling effort shows that the number of filtrations required to detect the total richness
is quite high but variable between sites (two to eight filtrations). Within the same site,
the eDNA approach does not distinguish between different habitats, showing data
homogenization at this scale. However, the habitats are distinguished as soon as they
have singularities in terms of hydrological connection to the main course (dead arms,
dig fields).
This work demonstrates that eDNA is a useful tool to answer ecological and
biodiversity questions both from a scientific and applied perspective (inventories,
detection of invasive, rare and / or endangered species...). Additional testing at
national / European scale and ultimately standardization will be required. The
extension of the eDNA approach to the detection of several taxonomic groups will
allow to gain understanding on full aquatic biodiversity on a river stretch. Finally, in
the long term, the use and interpretation of the signal will allow to better understand
relative abundances of taxa and to consider defining environmental quality indicators.
... 32 Mâle Femelle _________________________________________________________________________________________ 33 1996 1997 1998 1999 Linéaire (1995 Linéaire (1996) Linéaire (1997) Linéaire (1998) Linéaire (1999) 1996 1997 1998 1999 Linéaire (1995 Linéaire (1996) Linéaire (1997) Linéaire (1998) Linéaire (1999) ...
... 32 Mâle Femelle _________________________________________________________________________________________ 33 1996 1997 1998 1999 Linéaire (1995 Linéaire (1996) Linéaire (1997) Linéaire (1998) Linéaire (1999) 1996 1997 1998 1999 Linéaire (1995 Linéaire (1996) Linéaire (1997) Linéaire (1998) Linéaire (1999) ...
La grande alose est une espèce de poisson migrateur anadrome constituant une ressource halieutique. Dans la partie moyenne du bassin de la Loire, une technique patrimoniale de pêche des aloses est régulièrement utilisée, celle-ci, passive, permet d'appréhender le déroulement de la migration des géniteurs. Les données d'effort de pêche, les nombres de poissons capturés, couplées à des échantillonnages des caractéristiques des poissons sur plusieurs pêcheries permettent l'élaboration d'un indice annuel d'abondance des cohortes. L'évolution de cet indice, sur deux portions de Loire, l'une à l'aval de confluence avec la Vienne et l'autre à l'amont de cette confluence est analysée au regard de variables environnementales thermiques, hydrologiques et de continuité écologique. Sur l'ensemble de la période d'étude, de 1984 à 2010, les abondances des cohortes d'aloses ne peuvent être reliées à aucun des paramètres thermiques ou hydrologiques retenus. Si l'analyse de l'abondance est conduite en identifiant deux périodes, avant et après des travaux de continuité écologique, il est alors possible de reconnaître deux modes de fonctionnement des populations d'aloses avec une forte augmentation (x2 à x4) des indices d'abondance consécutive aux travaux. Pour la partie de Loire, en aval de la confluence avec la Vienne, l'abondance avant les travaux d'arasement du barrage de Maisons Rouges sur la Vienne) est conditionnée au dépassement d'un débit seuil, le quantile C90 de la Vienne, qui permettait alors un effacement des obstacles. Les aloses utilisaient des zones de reproduction fonctionnelles et ceci permettait un recrutement élevé de géniteurs. Après 1998, suite à l'arasement en 1998 du barrage de Maisons Rouges (244km de la mer), associé à l'équipement en passes à poissons sur les axes Creuse et Vienne, l'abondance des cohortes est liée aux variations de débit de la Vienne sur la saison de migration des géniteurs et non plus à un débit seuil. Pour la partie Loire en amont de la confluence avec la Vienne, les mêmes processus sont observés en lien avec le réaménagement de la passe à poissons de Vichy (650 km de la mer).
... Among all of the fish populations present, migrating fish were the most seriously affected. The shad (Alosa fallax rhodanensis) stock, the target species for the Rhône restoration program (Le Corre et al., 1997), decreased drastically, from 50 tons fished in the 1920's to less than 7 tons at present. The shad did not totally disappear, as 'substitute' spawning grounds appeared downstream of the first dam. ...
... Not as good a swimmer as the salmon, it avoids strong, highly oxygenated currents in which it becomes disoriented (Larinier and Travade, 1992). It is a Clupeidae with a total length between 0.25 and 0.45 m (Le Corre et al., 1997). The equation given by MacLennan and Simmonds (1992) in relation to Clupeidae [TS = 20log(L) -71.9 with L in cm and TS in dB], calculated in vertical emission, gives TS values of -43.94 and -38.8 dB, respectively, for the above lengths. ...
The application of fisheries acoustics in shallow waters opens new fields of observation and allows new methods for abundance estimates. In this paper we deal with echocounting of migrating fish crossing the Beaucaire-Vallabrègues lock, the first obstacle encountered on the Rhône, using a SIMRAD EY500 split-beam sounder, 70 kHz frequency. Two transducers sampled a section of water and evaluated approximately 35% of the lock section, based on a calibration sphere. The number of fish crossing the lock was calculated for each fish lock. Crossing data for the fish were recorded (dates, position, exit time). The present analysis did not allow the identification of the two major species that cross the dam: shad (Alosa fallax) and mullet (Mugil cephalus). The number of fish counted was positively correlated with the catches per unit effort (CPUE) by recreating fishermen below the dam and with increasing water temperature.
... Two species of shad were mentioned by Léger (1945/ 48), the Rhô ne twaite shad (Alosa agone) and allis shad (Alosa alosa). Today, only the Rhône twaite shad, considered as a discrete group within the species Alosa fallax, is present in the lower Rhô ne (Le Corre et al., 1997, 2000. Alosa alosa was stocked in the 1950s in the Rhô ne and a few hybrids (A. ...
... It is particularly interesting to note that the twaite shad used to migrate much further into the upper reaches of the Rhône and used to grow much larger than fish of the same species which are native to water bodies that drain into the Atlantic instead of the Mediterranean Sea (Le Corre et al., 1997). However, numerous continuum interruptions prevent these migratory fish from reaching the more Alpine stretches of the Rhône and its tributaries. ...
The chapter describes the fish fauna of the Alps, its diversity and fish ecological characteristics. After a general introduction, the history of settlement, which is characterised by the alternation of cold and warm periods, is described. The river basins of the Rhone, Rhine and Danube as well as the southern Alpine (mainly Italian) river catchments provide habitats for a diverse fish fauna characterised by numerous endemic species, some of which are described in more detail. The concluding subchapter discusses the main causes of threat to the Alpine fish fauna, all of which are of anthropogenic origin.
... In the western Mediterranean, the most important populations remains in the largest rivers in the region, i.e. the Rhône and the Ebro (Le Corre et al., 1997;López et al., 2007) though it is also present in the Têt, Agly, Aude and Hérault rivers (Le Corre et al., 2000;Mutel et al., 2017). In this area, some twaite shad populations were in sympatry with populations of the other anadromous European shad species, the allis shad Alosa alosa (Linnaeus, 1758). ...
Unexpected recent records of twaite shad (Alosa fallax) in two Northeastern Iberian rivers: recolonization or recovery of remnant populations? The presence of twaite shad Alosa fallax (Lacépède, 1803), an anadromous fish that migrates to lower and middle river reaches to spawn, has been reported in the Fluvià and Ter rivers (NE Spain) after several decades of absence of confirmed records. From 2015 to 2017 a total of 32 specimens, including one juvenile fish, were captured by angling in the River Fluvià, and a single individual was captured in the River Ter. The origin of these fish in the Fluvià may be the recovery of a scarce local population that remained undetected or a recolonization by individuals straying from neighbouring populations. The presence of a single individual in the Ter and the absence of records for over a century in this river suggest that this specimen may have come from a nearby population. If the establishment of a twaite shad population in the Fluvià is confirmed in the next few years, the construction of fish passages would increase the availability of spawning habitats and improve the species' conservation prospects.
RESUMEN Citas recientes inesperadas de saboga (Alosa fallax) en dos ríos del Noroeste de la Península Ibérica: ¿recolonización o recuperación de poblaciones remanentes? La presencia de saboga Alosa fallax (Lacépède, 1803), un pez anádromo que migra a los tramos bajos y medios de los ríos para desovar, se cita en los ríos Fluvià y Ter (NE de España) después de varias décadas de ausencia de registros confirmados. De 2015 a 2017, un total de 32 especímenes fueron capturados en el río Fluvià, incluyendo un juvenil, y un individuo en el río Ter. El origen estos peces podría ser la recuperación de una escasa población local que habría permanecido sin ser detectada, pero también existe la posibilidad de una recolonización de individuos errantes procedentes de poblaciones vecinas. La presencia de un solo individuo en el Ter, junto con la ausencia de citas por más de un siglo en este río, sugiere que el espécimen puede proceder de una población vecina. Si se confirma en los próximos años la presencia de una población estable de saboga en el Fluvià, la construcción de pasos de peces aumentaría la disponibilidad de hábitats de freza y podría mejorar sus perspec-tivas de conservación.
... Rameye et al. (1976) considered them to be rare. In a recent intensive study on the Rhône by Le Corre et al. (1997) none were recorded, suggesting that the population may now be extinct. A population of A. alosa may also exist in the River Argens (Didry 1953;Changeux and Pont 1995). ...
... Parmi toutes les populations de poissons présentes, les poissons migrateurs tels que l'esturgeon (Acipenser sturio), la lamproie marine (Petromyson marimus) et l'alose (Alosa fallax) (Figure 1a) furent les plus touchées. L'alose est devenue l'espèce cible de ce programme de restauration (LE CORRE et al., 1997). ...
Utilisées fréquemment en mer et en lac pour échantillonner les poissons, les techniques hydroacoustiques se développent de plus en plus dans les milieux de faible
profondeur. Le nombre de poissons qui franchissent l'écluse de Beaucaire-Vallabrègues, premier obstacle rencontré sur le Rhône, est estimé à l'aide d'un sondeur SIMRAD EY500,
fréquence 70 kHz, à faisceaux partagés(split-beam). Deux transducteurs échantillonnent une tranche d'eau évaluée à environ 35 % de la section de l'écluse. Le nombre de poissons franchissant l'écluse est calculé pour chaque éclusée dite à poissons. Les caractéristiques de franchissement des poissons (dates, position, durée de sortie) sont observées. Les analyses actuelles ne permettent pas de faire la distinction entre les deux principales espèces qui franchissent l'obstacle, l'alose (Alosa fallax) et le mulet (Mugil cephalus).
This chapter examines fifteen major river basins, six being transboundary, that encompass the biogeographical mosaic of the Balkan Peninsula and deliver over 80% of river flows into the Eastern Mediterranean Sea. Apart from a number of mountain river sections with spectacular wilderness landscapes still remaining intact, the majority of the Balkan rivers is under multiple human-induced pressures and increasingly threatened as a result of socioeconomic drivers combined with poor environmental planning and inadequate environmental legislation or enforcement. Lowland river sections face substantial hydro-morphological modifications and are at the greatest pollution risk as a result of insufficient treatment of municipal, mining and industrial wastewaters. New threats include many new dams, water transfers and hundreds of small hydro-electric projects. River flows and wetlands are declining at an alarming rate;; water quality deterioration is locally severe, while fragmentation of terrestrial and aquatic habitats even in protected areas cause irreversible disturbance to the connectivity, biodiversity and ecological quality of Balkan rivers despite recent integrated policy efforts such as the EU′s Water Framework Directive.
In Italy, as in several other circum-Mediterranean countries, there is a unique assemblage of endemic freshwater fishes. Speciation processes, especially of endemic primary or near-primary freshwater fish, most probably occurred during the Lago Mare era of the Mediterranean (about 5 million years bp). However, the present-day distribution patterns are surely the result of events that occurred more recently, from the Pleistocene until historical times. However, natural events are now being superseded by anthropogenic interference with fish faunas. Among the various negative human factors the most harmful is the introduction of non-native species, which in Italy are responsible for the present catastrophic situation. Of the 71 species currently with natural self-sustaining populations in Italian waters, only 45 are natives. Of the latter, only 16 (or fewer) have not been subjected to deliberate human transfers. In Italy there about 28 endemic Mediterranean taxa, but most have either been deliberately or accidentally introduced to areas outside their natural range. The result of this persistent practice on a little known and unique fish fauna is zoogeographic pollution, massive cases of hybridization and loss of genetic identity by local native populations. The problem of freshwater fish conservation is not a matter of public concern in Italy. Sport fishing has a political and economic value and introductions are legally carried out and ‘welcomed’ by most fishermen; most biologists and conservationists are either unaware or unconcerned.