Variability of amphidromous organism isotopic niches in three Guadeloupe rivers affected by damming and water catchment

Native fauna of the tropical volcanic part of Guadeloupe is amphidromous: juveniles born in rivers but that grow in the sea need to migrate upstream to colonise their adult habitat in rivers. This migration is affected by any human-made obstacles placed in their way. Moreover, on volcanic tropical islands, streams are the main source of water catchment for the human population. This deeply affects river hydrology and characteristics. Both damming and water catchment potentially affect community diversity and species demography, but they may also alter the trophic ecology of the river fauna. Using stable isotopes and the stable isotope Bayesian ellipses approach in R (SIBER), this study aimed to assess the isotopic niche variability of riverine fauna of three persistent small rivers of Basse-Terre Island (Guadeloupe) affected by damming and water catchment. Using electrofishing, decapods and fishes (gobies) of three rivers were sampled upstream and downstream of dams. Our results demonstrated that the variability of the isotopic niches was extremely high between rivers but varied less between stations of the same river. Our results revealed complex and river-specific effects and a pattern merged with natural variability. Our two hypotheses (i.e., increase of resources upstream of dams and differential responses of trophic guilds to damming and water catchment) were only weakly supported and never in an unambiguous manner. Our study showed that it is necessary to consider the ‘noise’ generated by natural variability to observe and understand changes in the trophic ecology of associated fauna in relation to damming and water catchment.Réponses démographique et adaptative aux perturbations de continuité écologique chez les espèces amphidromes (Gobiidae et Palaemonidae) (2016-05/projet227)

Alien marine fishes in Cyprus: update and new records

International audienceThe Mediterranean Sea, due to its connection to the Red Sea via the Suez Canal, its heavy maritime traffic, and the effects of climate change is a hotspot of invasion by alien species. A survey carried out around Cyprus during September 2014 documented the occurrence of 25 alien fishes. Seven Lessepsian migrants (Hippocampus fuscus Rüppell, 1838, Nemipterus randalli Russell, 1986, Ostorhinchus fasciatus (Shaw, 1790), Parupeneus forsskali (Fourmanoir & Guézé, 1976), Pomadasys stridens (Forsskål, 1775), Sphyraena obtusata Cuvier, 1829 and Spratelloides delicatulus (Bennett, 1832)) were recorded for the first time, increasing to 35 the number of alien fishes recorded around the island. Four of these first records can be considered as 'established', whereas the 2013 first record of Pterois volitans/miles is confirmed by new findings placing the species as newly 'established' in Cyprus. All the recorded alien fishes of Cyprus are Lessepsian migrants, 80% of which can be considered established and four of them are invasive. The rapid increase of alien fish species over time in Cyprus supports the accelerating tropicalisation process observed elsewhere in the Mediterranean over the last decades. Furthermore, the new finding of the tropical Atlantic immigrant Enchelycore anatina (Lowe, 1839) is documented

Effects of dams on demographic structures of amphidromous fish and crustacean species in Caribbean rivers

International audienceCaribbean island rivers are the home to migratory indigenous macro-fauna. Concurrently, they also serve as the main source of freshwater for human consumption. This production of drinking water involves the construction of a large number of structures across the riverbed, which can slow or even stop the migration of aquatic species. The resident river macro-fauna is composed of crustacean and fish species that all have a diadromous and mostly amphidromous life cycle, involving pro-larval drift downstream towards the sea, marine larval dispersal, followed by an upstream river migration to complete their growth and reproduction cycle. Our study compares, across three rivers on the island of Guadeloupe, the recruitment of five crustacean species and two fish species in the mouths of these rivers with species demographic distributions on either side of the major water withdrawal structure built along these rivers. Post-larval recruitment events were multispecific, discrete over time and their amplitude varied depending on the river. We show differential biological porosity of each obstacle according to species, revealing different specific crossing abilities. Our results also suggested that the impacts were not directly related to the height of the structure but that external, hydrological and environmental, conditions are involved. These achievements can be translated into operational measures such as the maintaining and monitoring of reserved minimal flows that are adapted to passways, as well as the setting up of protective measures for the natural environment.Les rivières caribéennes sont le lieu de vie d’une macrofaune indigène migratrice et aussi le principal lieu de prélèvement pour la production d’eau potable pour la population humaine. Cette production d’eau potable impli-que la construction d’un grand nombre d’ouvrages en travers du lit des rivières, qui peuvent ralentir ou stopper la migration des espèces. La macrofaune résidente est composée d’espèces de crustacés et de poissons qui ont tou-tes un cycle de vie diadrome et majoritairement amphidrome, impliquant une dévalaison larvaire vers la mer, une dispersion larvaire marine puis une montaison en rivière pour terminer leur croissance et se reproduire. Notre étude porte sur la comparaison du recrutement de cinq espèces de crustacés et deux espèces de poissons dans les embouchures de trois rivières proches, ainsi que sur la distribution démographique des différentes espèces de part et d’autre de l’ouvrage majeur de ces trois rivières. Les recrutements sont multispécifiques, discrets dans le temps et leur importance est variable selon l’embouchure. La porosité biologique de chaque obstacle est diffé-rente en fonction des espèces révélant différentes capacités de franchissement. Nos résultats suggèrent aussi que les impacts ne sont pas directement liés à la hauteur de l’ouvrage mais qu’interviennent des conditions externes à celui-ci, hydrologiques et environnementales. Ces acquis peuvent se décliner en mesures opérationnelles comme l’importance du maintien et de la surveillance de débits réservés adaptés et maîtrisés au niveau des passes, ainsi que la mise en place de mesures conservatoires de la ripisylve et de l’environnement naturel proch

Stable isotope ratios of C and N in diadromous fauna from Guadeloupe, French West Indies in 2017. Marine Data Archive.

Measurements of trophic markers performed in diadromous fauna from Guadeloupe. more This dataset contains measurements of stable isotope ratios of carbon and nitrogen made in 580 samples of diadromous fauna (459 individual specimens belonging to 14 taxa) and their food items (121 samples of drifting particulate organic matter, leaf litter or biofilm). Samples were taken in 3 rivers of Guadeloupe (French West Indies) between February and May 2017. In each river, 3 stations were sampled: one upstream from a water extraction dam, one downstream from each dam, and one at the mouth of the river. Analytical measurements were performed at University of Liège (Belgium)’s stable isotope facility (Laboratory of Oceanology, Stable Isotope in Environmental Sciences and Trophic Ecology workgroup, https://www.oceanobio.uliege.be/). More info about the studies and sample preparation can be found in the publication referenced below. The dataset consists of two files: one containing the data itself, and one describing all used terms (measurements or metadata, derived from Darwin Core standards, https://dwc.tdwg.org/terms/).Réponses démographique et adaptative aux perturbations de contuinité écologique chez les espèces amphidromes (Gobiidae et Palaemonidae) (2016-05/projet227)

Variability of amphidromous organism isotopic niches in three Guadeloupe rivers affected by damming and water catchment

Native fauna of the tropical volcanic part of Guadeloupe is amphidromous: juveniles born in rivers but that grow in the sea need to migrate upstream to colonise their adult habitat in rivers. This migration is affected by any human-made obstacles placed in their way. Moreover, on volcanic tropical islands, streams are the main source of water catchment for the human population. This deeply affects river hydrology and characteristics. Both damming and water catchment potentially affect community diversity and species demography, but they may also alter the trophic ecology of the river fauna. Using stable isotopes and the stable isotope Bayesian ellipses approach in R (SIBER), this study aimed to assess the isotopic niche variability of riverine fauna of three persistent small rivers of Basse-Terre Island (Guadeloupe) affected by damming and water catchment. Using electrofishing, decapods and fishes (gobies) of three rivers were sampled upstream and downstream of dams. Our results demonstrated that the variability of the isotopic niches was extremely high between rivers but varied less between stations of the same river. Our results revealed complex and river-specific effects and a pattern merged with natural variability. Our two hypotheses (i.e., increase of resources upstream of dams and differential responses of trophic guilds to damming and water catchment) were only weakly supported and never in an unambiguous manner. Our study showed that it is necessary to consider the ‘noise’ generated by natural variability to observe and understand changes in the trophic ecology of associated fauna in relation to damming and water catchment

Upstream/downstream food quality differences in a Caribbean Island River

International audienc

Detection of full and limited amphidromous migratory dynamics of fish in Caribbean rivers

International audienceAll native fishes living in the Caribbean island rivers are considered diadromous but few species have been validated as diadromous. In Guadeloupe (Lesser Antilles) as well as in the other tropical islands, the riverine habitats are subject to strong anthropogenic pressure due to resource modifications or dams. The management of fish biodiversity requires knowledge concerning their life history traits and behaviour that are still unknown for most species at a local scale and at the whole distribution area of the species. In a Guadeloupe river, we inferred the migratory patterns of four freshwater fishes common to Caribbean rivers by the analysis of otolith microchemistry. We found two species Eleotris perniger (Eleotridae) and Sicydium plumieri (Gobiidae) to be completely amphidromous with a marine larval phase and a freshwater adult phase. Agonostomus monticola (Mugilidae) was also found to be amphidromous in this system. The fourth species Gobiesox cephalus (Gobiesocidae) showed elemental ratios suggesting an estuarine larval phase and was defined as “limited amphidromous”. The identification of such life history traits, with limited dispersion abilities, argues for specific management measures in tropical island rivers at a basin scale for the conservation of biodiversity