Otolith shape analysis for three Sicyopterus (Teleostei: Gobioidei: Sicydiinae) species from New Caledonia and Vanuatu

Abstract

Otolith shape analysis has been used in a number of studies as an inexpensive and powerful method for categorising fish in individual stocks. Elliptical Fourier analysis was used on three different amphidromous Sicyopterus species. Sicyopterus lagocephalus is a widespread species while the other two have a limited distribution area, Sicyopterus aiensis being endemic to Vanuatu, and Sicyopterus sarasini to New Caledonia. Both endemics live in sympatry with the widespread species. The otolith shape of all fish sampled was a clear species differentiator, thereby demonstrating that otolith shape is species-specific. At an intraspecific level there are different river populations within samples from Vanuatu, indicating a western group and an eastern "central" group.These results are congruent both for the endemic species, S. aiensis and for the cosmopolitan species. Finally, we found that, for S. lagocephalus, the cosmopolitan species, New Caledonian samples are close to western Vanuatu samples, the latter two being well differentiated from the eastern "central" Vanuatu samples. The explanation for these results may lay either in the influence of environmental factors on the otolith shape, or in the influence of common early life history thus reflecting genetic factors, or a combination of both.

Morphological and Biometrical Characteristics on Otolith of Barbus tauricus Kessler, 1877 on Light and Scanning Electron Microscope

“…All calculations were performed with MINITAB 16.0 software package. The shape indices were calculated using the formulas below according to Tuset et al (2003) and Lord et al (2012) to describe shape of otoliths.…”

Identification of gerreid species (Actinopterygii: Perciformes: Gerreidae) from the Pacific coast of Mexico based on sagittal otolith morphology analysis

“…Such measurements were used to calculate dimensionless shape indices (Tuset et al 2003b, Ponton 2006, Pothin et al 2006 which are independent from differences in otolith size (Tuset et al 2006, Lord et al 2012, which include (Fig. 2, Table 2): rectangularity, roundness, circularity, form-factor, ellipticity, and aspect ratio.…”

“…Values close to zero indicate a good model fit and values ≈ 1 indicate lower discrimination power (Klecka 1980, Lord et al 2012. Another way to judge the relevance of a discriminant function is by examining the canonical correlation coefficient (r*; Klecka 1980).…”

“…In other studies the classification accuracy obtained using otolith descriptors has varied between 70% and 95% (Tuset et al 2006), indicating that otolith morphology can be used for identifying and separating Gerreidae species and it is likely that an individual is better characterized by its two otoliths rather than by only one of them (see Morat et al 2012). Although it has been established that otolith shape is markedly species-specific (L'Abée-Lund 1988, L'Abée-Lund and Jensen 1993), it is also known that there are external driving forces acting on otoliths shape, whatever the species (Lord et al 2012) including: age, sex, size, food availability, substrate, water temperature, as well as other biological and environmental factors, linked to the species and geographical sites (Tuset et al 2003a). In the presently reported study, considering that some of these factors are related to sample locations along the Pacific coast of Mexico, and that our analyses were made regardless of sex and minimizing size effect considering mostly adult specimens, there may be a confounding effect increasing the misclassification rate in some species (e.g., D. brevirostris: 24% and G. cinereus: 21%); Table 4).…”

“…Otoliths, the calcium carbonate structures located in fish inner ear, have been used as an auxiliary characteristic for identification of fishes in paleoichthyology (Nolf 1995) and stock recognition in fisheries management (Begg and Brown 2000, Tuset et al 2003a, Neves et al 2011, as well as a useful morphological character in taxonomy (Torres et al 2000a, Tuset et al 2006, systematics (Lombarte et al 1991, Smale et al 1995, Volpedo and Echeverría 2000, and food habits analysis (Radhakrishnan et al 2010). Otolith shape has long been known to be species-specific (L'Abée-Lund 1988) and less variable in growth than body growth, presumably because otoliths are internal organs contributing to audition and balance (Lord et al 2012), although its morphology can often vary geographically within a species (Lombarte and Lleonart 1993). In the majority of teleost species, sagittal otoliths are the largest pair, so they are the structures most frequently used in comparative studies because of the relative ease with which this structure can be reached (Nolf 1995).…”