Comparative analysis on otolith shape of <italic>Champsocephalus gunnari</italic> and <italic>Cryodraco antarcticus</italic> based on four morphological techniques

Abstract

To study the effectiveness of otolith morphological techniques on the population classification of Antarctic ice fish, based on the collected samples of <italic>Champsocephalus gunnari</italic> and <italic>Cryodraco antarcticus</italic>, 5 kinds of basic otolith morphological parameters were measured and converted into 7 morphological indicators, the differences in otolith morphology of two species were compared and analyzed, principal component analysis (PCA), stepwise discriminant analysis (SDA) and random forest (RF) were then used to discriminate the 77 elliptical Fourier harmonics of otolith morphological parameters. The results showed that the otolith parameters and body length of two species were significantly correlated (<italic>P</italic>>0.05). The body length of <italic>C</italic>. <italic>gunnari</italic> showed a power function relationship with some morphological parameters. While otolith length, otolith height, otolith area, otolith perimeter, otolith mass of <italic>C</italic>. <italic>antarcticus</italic> were all in logarithmic relationship with the body length. It could be seen that the otolith ring rate of <italic>C</italic>. <italic>gunnari</italic> was lower than that of <italic>C</italic>. <italic>antarcticus</italic>, compared to the otolith of <italic>C</italic>. <italic>antarcticus</italic>, the otolith of <italic>C</italic>. <italic>gunnari</italic> was rounder and more regular. The conventional morphological analysis could not discriminate the otoliths of two species. The PCA could discriminate the otoliths of two species, and the discriminant success rates of SDA and RF were 98.78% and 91.67%, respectively. SDA has its advantage in small sample size, but RF is suitable for large sample size.