Fish community structure in relation to environmental variation in coastal volcanic habitats

Abstract

International audienceThis study constitutes one of the few works conducted on the colonization of recent lava flows by fish communities in coral reef environment. It attempted to describe the mechanisms of colonization and environmental variables infuencing the structure of communities on the lava flows of the Piton de la Fournaise volcano at Reunion Island. It also proposed some hypotheses on the mechanisms of selection and speciation of endemic species of thesouthwestern Indian Ocean region, particularly diversified on the most recent lava flows of the Piton de la Fournaise, and provided a model of distribution of environmental and fish assemblage variables in four homogeneous patterns of colonization (landscapes) retained within the study area. The results showed fish community structure strongly related to measured environmental variables, of which depth, width of the island shelf, age of the lava flow and distance to the most recent lava flow were the most influential. It also appeared that the maximum endemic species richness was measured on the shallower stations, with narrow insular shelf, located on recent lava flows, near the lava flow from the eruption of 2007 (latest volcanic event). These characteristics define a harsh environment, to which endemic species seem well-adapted due in particular to their strong demographic and dietary flexibility. Finally, the patterns of colonization were characterized by significantly different environmental variables. The four homogeneous areas, defined by two geomorphological features, basalt blocks and drop-offs, nested within two locations, inside and outside the volcanic enclosure (current caldera), hosted fish communities whose dominant diets mainly depend on the nature, the abundance and the accessibility of available food resources. Overall, the study highlights that during early stages of ecological succession, site selection by fish communities is highly dependent on environmental constraints, specially of volcanic origin, but the physical habitat selection (geomorphology, substrate rugosity, percentage of soft substrate) seems to have littleimportance, while at least on the trophic structure and the distribution of endemic species

Habitat influence in the morphological diversity of coastal fish assemblages

“…Our results support the role of environmental variables as drivers of the ecological organization of coastal fish communities (Claudet et al, 2011;Pessanha Pais et al, 2010;Pinault et al, 2014). The assemblages inhabiting areas with mixture of bottoms showed higher number of species (CA15, CSEA15, CS15 or CR15), agreeing with many studies that assure that more complex substrates support richer and more diverse assemblages (Barros et al, 2001;García-Charton and Pérez-Ruzafa, 2001;La Mesa et al, 2010;Martins et al, 2013).…”

Responses of Herbivorous Fishes on Coral Reef Cover in Outer Island Indonesia (Study Case: Natuna Island)

“…The observer within 5 m on either side of transect was identified herbivore fishes. The UVC method is a nondestructive, capture-independent method, superior to collection techniques diversity and abundance of reef fishes although underwater visual censuses require little post-processing, whereas collections take many hours to complete [44]. This study was used three families herbivore fish that are most easily and rapidly identifiable by underwater visual census methods (Siganidae, Scaridae, and Acanthuridae) [10,45,41].…”

First record of the seagrass wrasse, Novaculoides macrolepidotus (Bloch, 1791) (Actinopterygii: Perciformes: Labridae), from Reunion Island, south-western Indian Ocean, with a brief description of its colour pattern variation, escape and reproductive behaviour

“…Most of the sampling effort was performed in coral reef habitats off the west and southwest coasts of the island. Recent works on nonreef habitats and other coastal segments (Pinault 2013, Pinault et al 2013a as well as on the volcanic rocks in the southeast (Bollard et al 2013, Pinault et al 2013b, 2014a, 2014b resulted in several additional species records (Quéro et al 2011, Quéro and Spitz 2012, Pinault et al 2014c, Wickel et al 2016. However, new records of fi sh species continue to be reported from coral reefs habitats .…”