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Étang-sur-Arroux, France

Teichert N.,British Petroleum | Teichert N.,University of Pau and Pays de lAdour | Teichert N.,French National Institute for Agricultural Research | Valade P.,Center Regional dApplication Aquacole | And 8 more authors.
Environmental Biology of Fishes

Freshwater populations of the Indo-pacific region are characterized by a large proportion of amphidromous species. In this paper, we analyse habitat selection by two amphidromous sympatric Gobiidae: Sicyopterus lagocephalus and Cotylopus acutipinnis in Reunion Island. A sampling method using Point Abundance Sampling (PAS) was conducted in 12 rivers. We used mixed logistic models in order to examine the presence probability of species according to location, downstream-upstream gradient, microhabitat variables (depth, velocity and predominant substrata) and presence of conspecifics and sympatric species. Presence probabilities varied between the sampled rivers. We observed a positive attraction between identical developmental stages of both species, which suggests that social interactions or similar preferences for environmental cues influenced their distribution. The presence probabilities of both species' juveniles decreased from downstream to upstream. We showed that traditional microhabitat variables weakly explained the spatial distribution of both S. lagocephalus and C. acutipinnis, in Reunion Island. We suggest that weak habitat selection for these species is consistent with the amphidromous life style because of the unpredictability of juvenile settlement and the extreme hydrological variations in tropical rivers. © 2013 Springer Science+Business Media Dordrecht. Source

Teichert N.,British Petroleum | Teichert N.,University of Pau and Pays de lAdour | Teichert N.,French National Institute for Agricultural Research | Valade P.,British Petroleum | And 5 more authors.

In the Indo-Pacific region, rivers are inhabited by amphidromous gobies. They are often subjected to a heavy fishing pressure, highlighting the urgent need to acquire knowledge on their biology for management purposes. This study investigated the reproductive strategy of Sicyopterus lagocephalus, a widespread amphidromous goby, in two rivers of La Réunion Island. Histological observations of ovarian samples and oocyte-size frequency distributions revealed that females had a group-synchronous ovarian follicle development (i.e., two cohorts of oocytes were distinguished simultaneously in ovaries). Females laid an entire clutch in a unique event (from 14,304 to 232,475 eggs) and then another batch of oocytes was recruited, showing that the annual fecundity is indeterminate. Ovarian growth was isometric at all oocyte development stages showing that the gonadosomatic index (GSI) is a good proxy of reproductive condition. The main reproductive season of S. lagocephalus spanned from early February to May with a narrower range upstream and a wider one downstream. Reproduction activity is mainly restricted by water temperatures in upstream areas, whereas it is likely influenced by female body condition and competition in downstream areas. The variability of reproductive traits leads to size structure variation in stocks of spawning females throughout the year. © 2013 Springer Science+Business Media Dordrecht. Source

Girard V.,IRSTEA | Monti D.,University of the French West Indies and Guiana | Valade P.,Center Regional dApplication Aquacole | Lamouroux N.,IRSTEA | And 2 more authors.
River Research and Applications

Hydraulic habitat models based on the preferences of species for the hydraulic characteristics of their microhabitats are frequently used to evaluate the impact on the habitat of a change in river flow regime. Their application in a tropical insular environment is still limited as little is known about the hydraulic preferences of species. Hydraulic preference models have been developed for 15 taxa (diadromous shrimps and fishes) sampled in 52 rivers in the Caribbean (the French West Indies) and the Indian Ocean (the Reunion island). Five datasets were used and group 8353 samples collected by electrofishing during 320 surveys (reach×date) performed between 1999 and 2011. Generalized additive models were used to link variations of taxa density within surveys to the hydraulic characteristics of the microhabitat (velocity, depth and substrate). Hydraulic preferences within each region (Caribbean and Indian Ocean) are significant for most of the taxa and vary little between rivers and surveys. The hydraulic variables explain up to 18.1% (univariate models) and 30.0% (multivariate models) of the deviance of densities within survey. Of the taxa selected, Atya scabra, Macrobrachium heterochirus, Xiphocaris elongata and the Sicydiinae are the most demanding. © 2013 John Wiley & Sons, Ltd. Source

Teichert N.,Association Reunionnaise de Developpement de lAquaculture ARDA | Teichert N.,University of Pau and Pays de lAdour | Teichert N.,French National Institute for Agricultural Research | Keith P.,French Natural History Museum | And 6 more authors.
Journal of Ethology

Amphidromous gobies are usually nest spawners. Females lay a large number of small eggs under stones or onto plant stems, leaves or roots while males take care of the clutch until hatching. This study investigates the breeding pattern and paternal investment of Sicyopterus lagocephalus in a stream on Reunion Island. In February 2007 and January 2010, a total of 170 nests were found and the presence of a goby was recorded at 61 of them. The number of eggs in the nests ranged from 5,424 to 112,000 with an average number of 28,629. We showed that males accepted a single female spawning in the nest and cared for the eggs until hatching. The probability for a nest to be guarded increased with the number of eggs within it, suggesting that paternal investment depends on a trade-off between the reproductive value of the current reproduction and future nesting events. We showed that large nest stones were occupied by large males (TL >80 mm), whereas smaller males (TL <50 mm) were found under smaller cobbles, probably because of male-male competition for available nests. Our results suggest that the male's choice relies upon a similarity to the female size, while the female's choice was based on both body and nest stone sizes. © 2013 Japan Ethological Society and Springer Japan. Source

Ellien C.,University Pierre and Marie Curie | Valade P.,Center Regional dApplication Aquacole | Bosmans J.,ARDA | Taillebois L.,British Petroleum | And 2 more authors.

The widely distributed amphidromous goby Sicyopterus lagocephalus needs drastic change of habitat to fulfil its life-cycle: adults live and spawn in rivers, where eggs hatch in pro-larvae that have to reach the sea in a narrow temporal scale, to acquire marine characteristics, and begin their oceanic dispersal as planktonic larvae. Post-larvae return to rivers where they recruit and grow to the adult reproductive stage. Such a life-cycle raises the question of salinity changes between these different developmental stages. Through an experimental approach, we observed and described the chronology in the appearance of marine larvae characteristics, according to 5 different salinities ranging, from 0% to 100% seawater. It appears that 5. lagocephalus needs an increase of salinity to acquire marine morphological characteristics, without being strict upon the salinity value itself. Whatever the tested salinity, the transformation of freshwater pro-larvae into marine larvae follows the same pattern within 48h: the yolk sac is absorbed until it only consists in the oil globule, pectoral fins develop and become functional, pigmentation spreads above the digestive tract, eyes become pigmented and functional, mouth and anus open, and the head appears more shaped. Pro-larvae behaviour evolves once in seawater: larvae remain on vertical position with their head oriented downwards (i.e., freshwater pro-larval behaviour) but they also spend more time horizontally, after the opening of the mouth, showing a behaviour of horizontal swimming, with acceleration phases, that may be interpreted as a hunting behaviour. Even a low salinity (i.e., less than 10% of seawater) is sufficient to induce these transformations, with the same timing than 100% seawater, leading to the conclusion that we did not underline a minimum salinity threshold for the acquisition of marine larvae morphological characteristics. Moreover, if the pro-larvae, after a first contact with brackish water, secondarily return to freshwater, their transformation is not stopped. However, pro-larvae that remain in 100% freshwater do not develop into marine larvae, neither in their morphological characteristics nor in their behaviour, and they die within 4 days. Source

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