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Bertucci F.,University of Liege | Lejeune P.,STARESO research station | Payrot J.,Natural Marine Reserve of Cerbere Banyuls | Parmentier E.,University of Liege
Journal of Fish Biology | Year: 2015

Sound production by the dusky grouper Epinephelus marginatus was monitored both in captivity and at two Mediterranean spawning sites during the summers of 2012 and 2013. The results of long-term passive acoustic recordings provide for the first time a description of the sounds produced by E. marginatus. Two types of sounds were mainly recorded and consisted of low-frequency booms that can be produced singly or in series with dominant frequencies below 100Hz. Recordings in captivity validated these sounds as belonging to E. marginatus and suggested that they may be associated with reproductive displays usually performed during early stages of courtship behaviour. This study also allowed the identification of a third, low-frequency growl-like type of sound typically found in other grouper species. These growls were, however, not recorded in tanks and it is cautiously proposed that they are produced by E. marginatus. Acoustic signals attributed to E. marginatus were produced throughout the spawning season, with a diel pattern showing an increase before dusk, i.e. from 1900 to 2200hours, before decreasing until the morning. The occurrence of sounds during the spawning season of this species suggests that they are probably involved in social activity occurring close to aggregation sites. Passive acoustics offer a helpful tool to monitor aggregation sites of this emblematic species in order to improve conservation efforts. © 2015 The Fisheries Society of the British Isles. Source

Parmentier E.,University of Liege | Michel L.,University of Liege | Michel L.,STARESO research station
Symbiosis | Year: 2013

Symbiosis can take different forms (parasitism, mutualism, commensalism, etc.) but boundaries between different types of symbiotic interactions are not well defined. The kinds of symbiotic associations between organisms cannot however be restricted to isolated and distinct categories. These associations are part of a broad continuum in which it is difficult to know where one type of association ends and another begins. Moreover, different scientists use the same term to mean different things or different terms to mean the same thing. This can obscure what is biologically important and what is not. This communication proposes a new classification scheme, which simply and comprehensively illustrates relationships between the various kinds of associations. The scheme illustrates relationships clearly and highlights the continuum between types of associations. It further indicates where modifications to the scheme are possible over time. The classification of the association between two organisms can be reduced to two factors: 1) the impact incurred by the host (benefit or damage) and 2) the relative duration of the association (RDA), i.e. the ratio of the duration of the association to the life expectancy of the symbiont. The conceptual figure provides concrete examples and illustrates some relationships that can change during different life stages. This figure should help teachers and students in the understanding of symbiosis, and could be a starting point for future discussions in the continuously developing research fields studying ecological and evolutionary implications of symbiotic relationships. © 2013 Springer Science+Business Media Dordrecht. Source

Marengo M.,CNRS Environmental Sciences | Marengo M.,University of Corsica | Pere A.,STARESO research station | Marchand B.,CNRS Environmental Sciences | And 4 more authors.
Bulletin of Marine Science | Year: 2016

The common dentex, Dentex dentex (Linnaeus, 1758), is an iconic coastal fish found in the Mediterranean Sea. Despite its ecological and economic importance, scientific data on its exploitation are scarce, especially off Corisca. The aims of our study were to: (1) analyze the relationship between the catch per unit effort (CPUE, by weight and number) and possible factors driving the trends observed; (2) examine temporal and spatial trends in CPUE; (3) examine the spatial distribution of fishing effort; and (4) compare the size distribution and age structure of catches. Sampling was conducted on fishing vessels operating from the main fishing harbors and in the main fishing sectors off Corsica between 2009 and 2013. CPUE varied spatiotemporally, but overall displayed annual stability. CPUE varied significantly as a function of month, strata, and depth. A seasonal pattern was observed with high catches during the spawning period (May) when size classes were mainly composed of mature individuals. Length and age frequency histograms after the spawning period (June-September) indicated that exploitation focused on small/young, immature individuals. Our spatial approach revealed a heterogeneous catch distribution and identified important exploitation areas. Results suggest that a combination of management tools and specific measures to safeguard the reproductive potential of this species should be implemented. © 2016 Rosenstiel School of Marine & Atmospheric Science of the University of Miami. Source

Giakoumi S.,Hellenic Center for Marine Research | Giakoumi S.,University of Queensland | Halpern B.S.,University of California at Santa Barbara | Halpern B.S.,Imperial College London | And 21 more authors.
Conservation Biology | Year: 2015

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components' vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions. © 2015 Society for Conservation Biology. Source

Velimirov B.,Medical University of Vienna | Lejeune P.,STARESO research station | Kirschner A.,Medical University of Vienna | Jousseaume M.,STARESO research station | And 6 more authors.
Estuarine, Coastal and Shelf Science | Year: 2016

A mass balance ecosystemic approach, based on bacterial carbon demands and primary production data, was used to investigate if the bacterial community (freewater bacterioplankton and benthic bacteria of the oxygenated sediment layer) could be sustained by the main primary producers (Posidonia oceanica and its epiphytes, adjacent macroalgae and phytoplankton communities; hereafter called the P. oceanica system) of a non-eutrophic Mediterranean bay. Unexpectedly, the findings of this study differed from previous works that used benthic incubation chamber and O2 optode methods. In this study, data were grouped in two categories, corresponding to two time periods, according to the seawater temperature regime (<18 °C or >18 °C): from May to October and from November to April. Between May and October, the produced benthic macrophyte tissues could not provide the carbon required by the bacteria of the oxygenated sediment layer, showing that the balance production of the investigated bay was clearly heterotrophic (i.e. negative) during this time period. In contrast, between November and April, benthic bacteria respiration nearly equated to carbon production. When integrating the open water carbon dynamics above the meadow in the model, a negative carbon balance was still observed between May and October, while a slight carbon excess was noticed between November and April. In the light of these findings, the carbon balance being negative on an annual basis, alternative carbon sources are required for the maintenance of the bacterial carbon production. © 2016 Published by Elsevier Ltd. Source

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