Otolith shape index: is it a tool for trophic ecology studies?

Abstract

The aim of this study was to test the effective separation of shape indices of otoliths of three species belonging to the family Sciaenidae before and after in vitro digestion. We measured 328 sagittal otoliths and applied six shape indices. Before the experiment, the aspect ratio (otolith height/otolith length%), circularity, ellipticity and relative surface of the sulcus acusticus were suitable for differentiating the species of genera Paralonchurus and Stellifer. Among the species of Stellifer, the aspect ratio and rectangularity were suitable. Otoliths exposed to in vitro digestion showed no significant differences in their morphometry before and after the experiment. After in vitro digestion, the aspect ratio and circularity were effective in separating Paralonchurus and Stellifer. However, none of the indices used in the present study were efficient to separate otoliths of congeneric species after in vitro digestion.

Invariant morphological descriptors from otolith shape in environment automatic classification

“…In the last 20 years, there has been a valuable contribution regarding otolith shape analysis and some types of morphometric descriptors have been reported with various purposes, such as studying morphometric relationships between right versus left otoliths Freire et al, 2017;Mille et al, 2015;Yedier & Bostanci, 2019); morphological identification and discrimination between close fish species or different fish populations (de Carvalho, Spach, et al, 2019;El habouz et al, 2016aEl habouz et al, , 2016bLadroit et al, 2017;Reig-Bolano et al, 2010;Skeljo & Ferri, 2012;Zorica et al, 2010); estimation of fish age based on morphometric analysis (See et al, 2016) or microstructures such as rings growth (Begg et al, 2001;Edwards et al, 2014;Nava et al, 2017;Yedier & Bostanci, 2020); an automatic taxonomic identification to identify biological species or structures (Parisi-Baradad et al, 2010;Salimi et al, 2016); studying how differences related to environmental and genetic aspects affect otoliths shape and growth (Jaramillo et al, 2014;Tuset et al, 2003;Vignon, 2012;Vignon & Morat, 2010); analyzing morphological features associated with the fish ecomorphologic type (Volpedo & Echeverrıá, 2003); as well as other events related to the life cycle of fish such as historical and biological characteristics, behaviour and activity (Montanini et al, 2017); further providing important information in decision-making about the exploitation vulnerability of species related to longevity and natural mortality ratio (Begg et al, 2005;Williams et al, 2015), and sustainable fishing activities (Iestyn-Map p, 2015). Some studies have been reported about left and right otoliths asymmetry, for example Lychakov et al (2006) show an asymmetry mesure obtained in rapport of otolith mass by mathematical models with asymmetry values among individual fish, and they reported that these asymmetry values are stable during a fish's lifetime.…”

“…There are morphometric internal descriptors from the whole object and external descriptors from the contour of the object, such as area, perimeter, length of main axes (major axis and minor axis), and Feret distances (length, width, diameter; Bostanci et al., 2015; Iestyn‐Mapp, 2015; Ladroit et al., 2017; Montanini et al., 2017; Ozpicak et al., 2019; Skeljo & Ferri, 2012; Tuset et al., 2003; Zorica et al., 2010). Classic geometric indexes show the relationships between otolith shape and conventional geometric shapes such as circularity, rectangularity, ellipticity, and bounding box (Bostanci et al., 2015; Bostanci & Yedier, 2018; de Carvalho, Spach, et al., 2019; de Carvalho, Volpedo, et al., 2019; Cerna et al., 2019; Iestyn‐Mapp, 2015; Ladroit et al., 2017; Montanini et al., 2017; Ozpicak et al., 2019; See et al., 2016; Skeljo & Ferri, 2012; Tuset et al., 2003; Zorica et al., 2010). Some authors consider aspect ratios, such as the relationship between otolith length and fish size or the otolith mass and fish size (de Carvalho, Spach, et al., 2019; de Carvalho, Volpedo, et al., 2019; Jaramillo et al., 2014; See et al., 2016).…”

Ontogenetic variation in the sagitta otolith of Centropomus undecimalis (Actinopterygii: Perciformes: Centropomidae) in a tropical estuary

“…Ontogenetic changes in otolith contour have been widely observed in several species (Capoccioni et al 2011, Vignon 2012. In C. undecimalis, variations in the contour throughout ontogeny were also found ( Table 1 and Table 2), studies that describe the ontogenetic variations in the shape of otoliths are of paramount importance for the identification of prey of ichthyophagous fishes (Bugoni and Vooren 2004, Carvalho et al 2019, Rodrigues et al 2019).…”

“…The same fish-species populations living in bodies of water with wide temperature ranges distinctly differ in their otolith shape (Leguá et al 2013). Recent studies have shown that environmental stress can cause morphological changes, even irregularities, in the deposition of crystals in otoliths (Carvalho et al 2019, Holmberg et al 2019.…”

Sagitta otolith of three demersal species in a tropical environment

“…The morphology and morphometry of otoliths may present sexual variation, as observed in Atherinella brasiliensis (Quoy & Gaimard, 1825), Micromesistius australis (Norman, 1937) and Porichthys notatus (Girard, 1854) (Carvalho & Correa, 2014;Leguá et al, 2013;Bose et al, 2016), as well as before and after the first maturity within the same species (Carvalho et al, 2020). The intraspecific morphologies and morphometric patterns of otoliths make them an important tool for studies of trophic ecology of ichthyophagous species (Miotto et al, 2017;Carvalho et al, 2019b). Some of the species identified as preys are also exploited in artisanal and recreational fisheries (Cattani et al, 2011;Freire et al, 2017;Passarone et al, 2019).…”