Ontogenetic and environmental effects on otolith shape variability in three mediterranean European eel (Anguilla anguilla, l.) local stocks

• Published in: Journal of Experimental Marine Biology and Ecology
• Main Authors: CAPOCCIONI, FABRIZIO, CICCOTTI, ELEONORA, Costa, C, Aguzzi, J, Menesatti, P, Lombarte,A
• Other Authors: Capoccioni, F, Lombarte, A, Ciccotti, E
• Format: Article in Journal/Newspaper
• Language: English
• Published: ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS 2011
• Subjects: Anguilla anguilla; Elliptic Fourier analysi; Habitat related change; Otolith shape; Size–shape relationshipe; Scopus Indexed keywords GEOBASE Subject Index: allometry; cluster analysis; coastal lagoon; data set; ee,lenvironmental effect,estuarine environment,genetic analysis; growth rate; habitat structure; marginal ice zone; marine ecosystem; migratory species; morphology; multivariate analysis; ontogeny; otolith; river water; shape; size Species Index: Anguilla anguilla; Animalia; Settore BIO/07 - ECOLOGIA; European eel
• Online Access: http://hdl.handle.net/2108/19370; https://doi.org/10.1016/j.jembe.2010.11.011

Otolith morphology is an efficient tool for the discrimination of fish stocks, populations and species when comparative genetic data are not available. Currently, the relationship between environmental factors and otolith shape is poorly characterized for the European eel (Anguilla anguilla), a highly migratory catadromous species constituting a single, randomly mating stock. The present study analyses the differences in otolith morphology between three Mediterranean eel local stocks from different environmental contexts (i.e. two brackish lagoons and one river). The relationship between otolith shape and otolith size was studied by means of Elliptic Fourier analysis and multivariate statistics. Otolith profile was digitally acquired and Cartesian coordinates were extracted. Partial Least Square (PLS) analysis pointed to continuous allometric growth in size and shape in otoliths from all three sites. In the three environments, shape variations occurred during growth as indicated by the presence of a significant and positive relationship between otolith size and the first PLS latent vector (i.e. which bears most of the information regarding otolith outline). Differences between smaller and larger sized otoliths were investigated using PLS Discriminant Analysis (PLSDA) and cluster analysis. Results indicate that otolith shape is highly uniform at smaller than at larger sizes. These shape differences apparently overlap the initial differentiation of the small otolith outlines acquired by eels during the growing phase as elvers in the marine environment. Data were discussed considering that the physical and chemical habitat variability in brackish lagoons and river could underlie a marked change in otolith shape during the animals' growth.