Spatial structure and distribution of small pelagic fish in the northwestern Mediterranean Sea

Understanding the ecological and anthropogenic drivers of population dynamics requires detailed studies on habitat selection and spatial distribution. Although small pelagic fish aggregate in large shoals and usually exhibit important spatial structure, their dynamics in time and space remain unpred...

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Bibliographic Details
Published in:	PloS one 2014-11, Vol.9 (11), p.e111211-e111211
Main Authors:	Saraux, Claire, Fromentin, Jean-Marc, Bigot, Jean-Louis, Bourdeix, Jean-Hervé, Morfin, Marie, Roos, David, Van Beveren, Elisabeth, Bez, Nicolas
Format:	Article
Language:	eng
Subjects:	Acoustic surveying Acoustics Anchovies Animal Distribution Animals Anthropogenic factors Biology and Life Sciences Biomass Clupeidae Clupeiformes Dynamic structural analysis Earth Sciences Ecological monitoring Ecology and Environmental Sciences Ecosystem Ecosystems Engraulis encrasicolus Exploitation Fish Fish industry Fisheries Fishes Geostatistics Habitat selection Habitats Interspecific Life Sciences Mediterranean Sea Merluccius merluccius Oceanography Pelagic zone Population Density Population Dynamics Population studies Sardina pilchardus Sardines Scales Sciences of the Universe Shoals Spatial distribution Species Sprattus sprattus Studies
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Summary:	Understanding the ecological and anthropogenic drivers of population dynamics requires detailed studies on habitat selection and spatial distribution. Although small pelagic fish aggregate in large shoals and usually exhibit important spatial structure, their dynamics in time and space remain unpredictable and challenging. In the Gulf of Lions (north-western Mediterranean), sardine and anchovy biomasses have declined over the past 5 years causing an important fishery crisis while sprat abundance rose. Applying geostatistical tools on scientific acoustic surveys conducted in the Gulf of Lions, we investigated anchovy, sardine and sprat spatial distributions and structures over 10 years. Our results show that sardines and sprats were more coastal than anchovies. The spatial structure of the three species was fairly stable over time according to variogram outputs, while year-to-year variations in kriged maps highlighted substantial changes in their location. Support for the McCall's basin hypothesis (covariation of both population density and presence area with biomass) was found only in sprats, the most variable of the three species. An innovative method to investigate species collocation at different scales revealed that globally the three species strongly overlap. Although species often co-occurred in terms of presence/absence, their biomass density differed at local scale, suggesting potential interspecific avoidance or different sensitivity to local environmental characteristics. Persistent favourable areas were finally detected, but their environmental characteristics remain to be determined.
ISSN:	1932-6203 1932-6203