@article {7397, title = {Structure of small tropical island freshwater fish and crustacean communities: A niche-or dispersal-based process?}, journal = {Biotropica}, year = {2020}, month = {Jan-10-2021}, abstract = {Determining the relative importance of niche- and dispersal-based processes in the structuring of animal communities is central in ecology. Freshwater fish and crustacean communities of small tropical islands can bring new insights for understanding these processes as all their species present a pelagic larval stage which gives them important dispersal capacities. Consequently, we hypothesized that dispersal-based process may be preponderant for structuring these communities from the regional to the local, that is, survey site, scales. Gradient forest analyses allowed us to model the effect of 12 environmental variables on freshwater taxa abundances in two southwestern Indian Ocean islands: Mayotte (26 taxa) and Reunion (21). A total of 153 surveys in Mayotte and 266 in Reunion were used for building the models. Despite the strong heterogeneity of environmental conditions between the two islands, the main factors structuring freshwater fish and crustacean communities in both islands were the elevation and the slope of the sites. The observed structure appeared more pronounced for predatory species than for primary consumers and omnivores. As predators generally have limited locomotor capacities, it is concluded that dispersal-based process structures these communities not only at large geographical scales but also at the intra-watershed scale, by limiting the inland penetration (or dispersion) of species in relation to their locomotor capacities. However, more knowledge concerning ecological traits and taxonomic status of many species is needed to confirm this assumption.
}, keywords = {abundances, diadromy, environmental gradients, Migration, taxonomic richness, western Indian Ocean}, issn = {0006-3606}, doi = {10.1111/btp.12865}, url = {https://onlinelibrary.wiley.com/doi/10.1111/btp.12865}, author = {Lagarde, Rapha{\"e}l and Teichert, Nils and Valade, Pierre and Ponton, Dominique} } @article {6730, title = {When {\textquotedblleft}safe{\textquotedblright} dams kill: Analyzing combination of impacts of overflow dams on the migration of silver eels}, journal = {Ecological Engineering}, volume = {145}, year = {2020}, pages = {105741}, abstract = {1. The drastic decline in European eel\ Anguilla anguilla\ stock is now widely recognized. However, while various causes for this decline have been identified, the relative importance of each cause remains unclear.

2. During the catadromous migration of silver eels, the negative impact of dams is frequently highlighted, but mainly for powered dams (with turbines) or where connectivity is completely ruptured. Mechanical impact due to turbine blades is often considered the most important cause of mortality of silver eels during downstream migration. Consequently, non-powered dams equipped with spillways are often considered safe for the passage of migrating silver eels.

3. We hypothesized that, to understand the negative impacts of dams, a much wider context must be considered than turbine mortality alone. Using an acoustic telemetry survey of silver eels, we demonstrated the negative effects of non-powered dams on downstream migration.

4. Five main impacts on eel populations were highlighted: (i) the attenuation or loss of triggering factors, leading to an absence of or delay in migration; (ii) extra delays and extra distances travelled when crossing the dam; (iii) extra energetic costs of the additional distance travelled as result of exploring the dam and the reservoir to find other escape passages; (iv) the selection of a more risky behavioral phenotype, i.e., bold eels; and (v) direct blocking once migration has started. Mortality was evaluated as a supplementary impact. Some of these effects (attenuation of triggers, extra delays to cross the dam) might be more important than the same effect from powered dams, probably due to the constant high water discharge required for turbines that facilitate the passage of eels.

5. As these {\textquotedblleft}safe{\textquotedblright} dams are very widespread, they must be considered a potential threat to effective eel conservation.}, keywords = {Acoustic telemetry, Migration, mortality, Non-powered dams, Silver eels, Turbines drinking water intake}, issn = {0925-8574}, doi = {https://doi.org/10.1016/j.ecoleng.2020.105741}, url = {http://www.sciencedirect.com/science/article/pii/S092585742030029X}, author = {Thomas Trancart and Alexandre Carpentier and Anthony Acou and Fabien Charrier and Virgile Mazel and Valentin Danet and Eric Feunteun} } @article {6737, title = {Distribution of anguillid leptocephali and possible spawning areas in the South Pacific Ocean}, journal = {Progress in Oceanography}, volume = {180}, year = {2019}, pages = {102234}, abstract = {Seven South Pacific anguillid eel species live from New Guinea to French Polynesia, but their spawning areas and life histories are mostly unknown despite previous sampling surveys. A July{\textendash}October 2016 research cruise was conducted to study the spawning areas and times, and larval distributions of South Pacific anguillid eels, which included a short 155{\textdegree}E station-line northeast of New Guinea and five long transects (5{\textendash}25{\textdegree}S, 160{\textdegree}E{\textendash}140{\textdegree}W) crossing the South Equatorial (SEC) and other currents. This survey collected nearly 4000 anguilliform leptocephali at 179 stations using an Isaacs-Kidd Midwater Trawl accompanied by 104 CTD casts. Based on morphometric observations and DNA sequencing, 74 anguillid leptocephali were collected, which in the southern areas included 29 larvae of six species: Anguilla bicolor pacifica, A. marmorata, A. australis, A. reinhardtii, A. megastoma,and A. obscura (all anguillid species of the region were caught except A. dieffenbachii). Small A. australis (9.0{\textendash}16.8\ mm) and A. reinhardtii (12.4, 12.5\ mm) leptocephali were collected south of the Solomon Islands, other A. australis (10.8{\textendash}12.0\ mm) larvae were caught northwest of Fiji along with an A. obscura (20.0\ mm) larva, and an A. marmorata (7.8\ mm) larva was collected near Samoa. Considering collection sites, larval ages from otolith analysis, and westward SEC drift, multiple spawning locations occurred from south of the Solomon Islands and the Fiji area (16{\textendash}20\ days old larvae) to near Samoa (19\ days old larva) during June and July in areas where high-salinity Subtropical Underwater (STUW, 150\ m depth) and the warm, low-salinity surface Fresh Pool were present. Five long hydrographic sections showed the strong Fresh Pool in the west and the STUW formation area in the east.}, keywords = {Early life history, Freshwater eels, Migration, otolith, South Pacific, Spawning}, issn = {0079-6611}, doi = {https://doi.org/10.1016/j.pocean.2019.102234}, url = {http://www.sciencedirect.com/science/article/pii/S0079661119304148}, author = {Mari Kuroki and Michael J. Miller and Eric Feunteun and Pierre Sasal and Timothy Pikering and Yu-San Han and Elisabeth Faliex and Anthony Acou and Aur{\'e}lie Dessier and Robert Schabetsberger and Shun Watanabe and Tatsuya Kawakami and Hiroaki Onda and Takatoshi Higuchi and Aya Takeuchi and Madoka Shimizu and Chinthaka A. Hewavitharane and Seishi Hagihara and Terumasa Taka and Shingo Kimura and Noritaka Mochioka and Tsuguo Otake and Katsumi Tsukamoto} } @article {6047, title = {The global geography of fish diadromy modes}, journal = {Global Ecology and Biogeography}, year = {2019}, abstract = {

Aim: Geographical gradients in resource production are likely to translate into macroecological patterns in the biodiversity of migratory organisms, but few studies have addressed this question at a global scale. Here, we tested a hypothesis based on uncoupled latitudinal gradients in marine and freshwater primary productivities aimed at explaining where (e.g., at which latitude) and at which stage of the life cycle (larvae, amphidromy; juvenile, catadromy; or adult, anadromy) migration from ocean to freshwater occurs (diadromy).

Location: Global.

Time period: Current.

Major taxa studied: Fishes.

Methods: We modelled, using multinomial regressions, the proportion of catadromous, anadromous and amphidromous species in 994 river basins as a function of freshwater and marine net primary productivities (NPP; in milligrams of carbon per square metre per day) and additional biotic and abiotic variables. Using data extracted from the Global Biodiversity Information Facility (GBIF) database, we tested whether diadromous, catadromous and amphidromous species differed with respect to the NPP of their marine and freshwater occurrences.

Results: Among diadromous species, anadromous species are present in higher proportions when conditions for growth are more favourable in the sea (higher productivity, higher temperature and lower number of competitors) than in freshwaters. The model reconstructs the latitudinal pattern observed in the proportion of anadromous species, including an asymmetry between the Northern and Southern Hemispheres. According to GBIF occurrences, the ratio of marine over freshwater productivity is higher for anadromous species compared with catadromous and amphidromous species.

Main conclusions: Our results support the hypothesis stating that migration between ocean and freshwater occurs by choosing the biome that optimizes pre-reproductive growth and is one more example of the importance of primary productivity in shaping large-scale community patterns. This result suggests that some diadromous fish populations and species may suffer from anticipated climate change if interbiome productivity gradients are affected.

}, keywords = {amphidromy, anadromy, Biogeography, catadromy, dispersal, GBIF database, Last Glacial Maximum, latitudinal gradient, Migration, Species richness}, doi = {DOI: 10.1111/geb.12931}, author = {Chalant, Ana{\"\i}s and J{\'e}z{\'e}quel, C{\'e}line and Philippe Keith and Bernard Hugueny} } @article {6668, title = {Modelling the functioning of a coupled microphytobenthic-EPS-bacterial system in intertidal mudflats}, journal = {Marine Environmental Research}, volume = {150}, year = {2019}, abstract = {A mechanistic and biogeochemical model was developed to analyze the interactions between microphytobenthos (MPB), bacteria and nutrients in a tidal system. Behavioral vertical migration was hypothesized as being controlled by exogenous factors (tide and light) but also by endogenous factors (carbon and nitrogen requirements). The secretion of Extracellular Polymeric Substances (EPS) during photosynthesis (overflow metabolism) and migration of diatoms was also formulated. Similarities in MPB dynamics between observations and simulations support the assumption that carbon and nitrogen ratios are additional key processes behind the vertical migration of diatoms in the sediment. The model satisfactorily reproduced the three growth phases of the MPB development observed in a mesocosm (the lag phase, the logarithmic growth, and the plateau). Besides, nutrient availability, which could be induced by faunal bioturbation, significantly determined the extent of MPB biomass and development. The plateau phase observed in the last days of simulations appeared to be attributed to a nutrient depletion in the system, emphasizing the importance of nutrient availability. The model, although improvable especially on the formulation of the EPS excretion and bacteria development, already updated understanding of several aspects of benthic-system functioning during experimental conditions. {\textcopyright} 2019 Elsevier Ltd}, keywords = {Bacillariophyta, bacteria, Bacteria (microorganisms), bacterial growth, bacterium, Biogeochemical modeling, biogeochemistry, Biomass, Carbon, Carbon and nitrogen, Carbon and nitrogen ratios, Diatom, diel vertical migration, exopolymer, Experimental conditions, Extracellular polymeric substances, intertidal environment, intertidal zone, light, mesocosm, microbial community, Microphytobenthos, Migration, modeling, mudflat, Nitrogen, nonhuman, Nutrient availability, Nutrients, nutritional requirement, organic carbon, organismal interaction, Photosynthesis, Phytobenthos, Phytoplankton, polymer, Review, simulation, tide, vertical migration}, issn = {01411136}, doi = {10.1016/j.marenvres.2019.104754}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0141113619300704}, author = {Rakotomalala, C and Katell Guizien and Karine Granger{\'e} and S{\'e}bastien Lefebvre and Christine Dupuy and Francis Orvain} } @article {6752, title = {Silver eel downstream migration in the River Rhine, route choice, and its impacts on escapement: A 6-year telemetry study in a highly anthropized system}, journal = {Ecological Engineering}, volume = {123}, year = {2018}, pages = {202 - 211}, abstract = {Several routes are available for the downstream migration of silver eels in the river Rhine system. Very different effects on migration success can result from this choice, such as speed and migration duration or escapement rate. We studied the downstream migration of silver eels in a river section with two different routes. The first route is the initial and old riverbed, with two dams equipped with two rather small or medium sized hydropower plants (HPPs) located at the beginning and at the exit of the bypass stretch. Both HPPs have small bar spacing (10 mm and 20 mm, respectively) and the second HPP has two downstream bypasses. The second route is a power canal, supplying four major HPPs (maximum discharge capacity = 1400 m3 s-1) and a nuclear power plant with cooling water. Firstly, this study focused on highlighting the factors influencing route choice. Secondly, we focused on the consequences of this choice. We demonstrate that water current management in the old riverbed at the study site had a 40\% higher negative effect on eel survival than that by a consecutive passage in four turbines.}, keywords = {Escapement, Migration, Path selection, Rhine river, Silver-eel, Telemetry}, issn = {0925-8574}, doi = {https://doi.org/10.1016/j.ecoleng.2018.09.002}, url = {http://www.sciencedirect.com/science/article/pii/S0925857418303318}, author = {Thomas Trancart and St{\'e}phane T{\'e}tard and Anthony Acou and Eric Feunteun and Fr{\'e}d{\'e}ric Schaeffer and Eric de Oliveira} } @article {4280, title = {Trans-Amazonian natal homing in giant catfish}, journal = {Journal of Applied Ecology}, volume = {53}, year = {2016}, pages = {1511-1520}, abstract = {

1.Knowledge of fish migration is a prerequisite to sustainable fisheries management and preservation, especially in large international river basins. In particular, understanding whether a migratory lifestyle is compulsory or facultative, and whether adults home to their natal geographic area is paramount to fully appraise disruptions of longitudinal connectivity resulting from damming.2.In the Amazon, the large migratory catfishes of the Brachyplatystoma genus are apex predators of considerable interest for fisheries. They are believed to use the entire length of the basin to perform their life cycle, with hypothesized homing behaviours. Here we tested these hypotheses, using the emblematic B. rousseauxii as a model species.3.We sampled adults close to major breeding areas in the Amazon basin (upper Madeira and upper Amazonas) and assessed their lifetime movements by measuring variations in 87Sr/86Sr along transverse sections of their otoliths (ear stones) using laser ablation multicollector mass spectrometry (LA-MC-ICPMS).4.We demonstrate that larvae migrate downstream from the Andean piedmont to the lower Amazon, where they grow over a protracted period before migrating upstream as adults. Contrary to prevailing inferences, not all fish spend their nursery stages in the Amazon estuary. By contrast, the passage in the lower or central Amazon seems an obligate part of the life cycle. We further evidence that most adults home to their natal geographic area within the Madeira sub-basin. Such long-distance natal homing is exceptional in purely freshwater fishes.5.Synthesis and applications. By using otolith microchemistry, we were able to demonstrate a seemingly compulsory basin-wide migratory life cycle of large Amazonian catfishes. This makes them the organisms performing the longest migrations (\>8000 km) in fresh waters. This exceptional life history is already jeopardized by two dams recently built in the Madeira River, which block a major migration route and access to a substantial part of their spawning grounds. Major impacts can be anticipated from the current and forthcoming hydroelectric development in the Amazon basin, not only on the populations and fisheries of this apex predator, but also on Amazonian food webs through trophic cascades.This article is protected by copyright. All rights reserved.

}, keywords = {87Sr/86Sr ratios, Amazon, anthropogenic activities, Brachyplatystoma spp, freshwater fish, giant catfish, hydroelectric dams, Migration, otoliths}, issn = {1365-2664}, doi = {10.1111/1365-2664.12665}, url = {http://dx.doi.org/10.1111/1365-2664.12665}, author = {Fabrice Duponchelle and Marc Pouilly and Pecheyran, Christophe and Hauser, Marilia and Renno, Jean-Francois and Panfili, Jacques and Darnaude, Audrey M. and Garc{\'\i}a-Vasquez, Aurea and Carvajal-Vallejos, Fernando and Carmen Garc{\'\i}a-D{\'a}vila and Doria, Carolina and B{\'e}rail, Sylvain and Donard, Ariane and Sondag, Francis and Santos, Roberto V. and Jesus Nu{\~n}ez-Rodriguez and Point, David and Labonne, Maylis and Baras, Etienne} }