Testing otolith morphology for measuring marine fish biodiversity

Abstract

Abstract.To check the suitability of otoliths for measuring biodiversity, the contour and shape of the sulcus acusticus of sagittal otoliths were described using geometric morphological analysis. Thirteen and fourteen points were used to define these structures respectively. Three current coastal fish assemblages of the north-western Mediterranean were selected for the present study. The results demonstrate that the relative warps generated in the geometric analysis explained both characteristics related to contour and the otolith sulcus. A comparative study with body fish shape using morphospaces and clusters revealed that otolith shape is a better variable for explaining the ecological structure of a fish assemblage. Moreover, three morphological indices (morphological richness (MR), morphological disparity and the morphogeometric index) were estimated from relative warps of otoliths and were compared with ecological, taxonomic, functional and morphological (from body shape) indices. MR increased with functional diversity and average taxonomic distinctness, reflecting the ecological and taxonomic character of otolith morphology. These findings suggest that otoliths could be a useful tool for studying the diversity of present and past fish assemblages.

Enigmatic ear stones: what we know about the functional role and evolution of fish otoliths

“…Hence, the ratio of otolith area to the area of the sulcus or fossa, i.e. increased relative sulcus or fossa area (Lombarte & Tuset, ; Tuset et al, ), was assumed to result in altered (possibly improved) hearing abilities (Ramcharitar et al, ; Schulz‐Mirbach et al, ; see also Gauldie, ). Ecomorphological studies indicate that the ratio of sulcus size (2D sulcus area, used as a proxy for macula size) to otolith size (area of the macula‐oriented face of the otolith) seems to be correlated with habitat features such as water depth (Lombarte & Fortuno, ), food or spatial niches (Aguirre & Lombarte, ), and mobility (Lombarte & Popper, ), but may also vary during ontogeny in some species [ e.g .…”

“…However, in a recent innovative approach, Tuset et al . () developed a landmark/semilandmark‐based method to extract information about the 2D outline of the sulcus acusticus in medial view and demonstrated its applicability in a comparative approach involving 61 species from the Mediterranean Sea. This method (Tuset et al, ; see also Sadighzadeh et al, ) could be combined with evaluation of the depth of the sulcus using high‐resolution microCT imaging (Schulz‐Mirbach et al, ).…”

“…Functional interpretations of the potential adaptive significance of such traits are hampered by uncertainties regarding the mechanical properties of the otolithic membrane (see Section III.4a) and difficulties in reliably quantifying the dimensions of the sulcus acusticus and the fossa acustica. However, in a recent innovative approach, Tuset et al (2016a) developed a landmark/semilandmark-based method to extract information about the 2D outline of the sulcus acusticus in medial view and demonstrated its applicability in a comparative approach involving 61 species from the Mediterranean Sea. This method (Tuset et al, 2016a; see also Sadighzadeh et al, 2014) could be combined with evaluation of the depth of the sulcus using high-resolution microCT imaging (Schulz-Mirbach et al, 2013a).…”

Sexual dimorphism in the sonic system and otolith morphology of Neobythites gilli (Ophidiiformes)

“…Some studies suggest that there is a relationship between otolith features and hearing ability but others support it is related to habitat (Parmentier, Vandewalle & Lagard ere, 2001). Within species, otolith can show differences related to the fish size but not between conspecifics having the same size if exposed to the same environmental factors, meaning they can be reliable tools to study fish diversity (Tuset et al, 2016).…”

Fish otoliths as indicators in ecosystem based management: results of the 5th International Otolith Symposium (IOS2014)

“…Brophy et al (2016) analysed otolith shape of bluefin tuna and illustrated how these methods can be used to improve estimates of population mixing rates and incorporate these into stock assessment. Diversity of fish assemblages may also be studied using otolith shape proxies (Tuset et al 2016). Otolith shape analysis methods are moving rapidly, and techniques from other disciplines are being applied to characterise otolith outlines (Harbitz 2016) and also 3-D otolith surfaces (Marti-Puig et al 2016).…”