Application of otolith morphometry for the study of ontogenetic variations of Odontesthes argentinensis

Abstract

The study of otolith morphometry is a tool widely used in numerous studies of fish populations (fish stocks, taxonomic, ecological, ontogeny, among others). The aim of this study was to detect ontogenetic variations in the otolith of Odontesthes argentinensis through the application of traditional and geometric morphometry and the association of these variations with ecological and trophic habits of the species. Fish (52 to 360 mm TL) were collected seasonally between years 2013-2016 in the southwest coast of the Atlantic Ocean (36°39'30.96"S -56°40'40.09"W). Otolith shape indices (circularity, rectangularity, aspect ratio and surface occupied by sulcus) and Fourier descriptors were measured and compared through ontogenetic stages (I, II and III). The three stages analysed in the present study were differentiated by both traditional and geometric morphometry. The four analysed indices showed significant differences between stages (ANOVA Kruskal Wallis test, P < 0.001) and a simultaneous analysis of the morphometric variables also showed significant differences (Hotelling's T 2 < 0.001). The quadratic discriminant analysis performed on the Fourier descriptors showed a clear separation for each defined group. Therefore, the use of both methodologies simultaneously could be considered robust to evaluate the ontogenetic variations in this species. The observed changes could be associated to changes in the habitat throughout its development, to the sexual maturity of fish and to dietary shifting of these organisms.

Unravelling Stock Spatial Structure of Silverside Odontesthes argentinensis (Valenciennes, 1835) from the North Argentinian Coast by Otoliths Shape Analysis

“…The values of the morphometric indices of otolith shape obtained by Biolé et al [37] in silversides of La Lucila del Mar are different in relation to those obtained in this work. These differences may be due to the existence of a latitudinal gradient in the species.…”

“…Marine and euryhaline coastal species inhabit dynamic environments so they generally show high plasticity [56], such as atherinids, mugilids and sardines [17,37,[57][58][59]. This plasticity can be reflected in otoliths.…”

“…Morphometric variables, such as otolith length (OL mm), width (OW mm), area (OA mm 2 ) and perimeter (OP) in mm, were obtained from the contours of otoliths using ShapeR [42]. Four morphometric indices (MI) were calculated: (i) Circularity (OP 2 /OA) [37,48,49]; (ii) rectangularity (OA/(OW × OL)) [37,48,49]; (iii) aspect ratio (OW/OL), [37]; (iv) roundness (4 × OA)/(π × OL 2 ) [13]. All morphometrical variables fitted a normal distribution and homogeneity of variance (Shapiro-Wilk, p > 0.05; Levene, p > 0.05).…”

“…Indices were corrected to eliminate possible allometry effects in otolith shape related to fish body size, for a proper comparison between groups; the formula: y' = yi × (x0/xi)b was used, in which y' is the corrected predictive variable, yi is the original value of the obtained index, x0 is a referential standard length (SL) value (SL minimum = 142 mm), xi is the original SL value, and b is the Huxley coefficient of each regression index to SL [37,49,50].…”

“…Studies show how the otoliths of this species change during growth, using morphology and geometric morphometry [36,37]. Levy et al [26], using the parasitic community of O. argentinenesis specimens caught in the Mar del Plata area (38 • 02 S, 57 • 31 W) and in the San Matías Gulf (40 • 50 S, 64 • 50 W), found that the evaluated individuals belonged to two different stocks.…”