Abstract:

Using samples collected from the South Shetland Islands and South Georgia during March–April 2014 and April–September 2015, this study compares the differences in otolith shape for two icefish species (Mackerel icefish Champsocephalus gunnari and crocodile icefish Chionobathyscus dewitti) using seven morphological parameters which transformed from five basic shape measurements. Population discrimination has also been conducted using Fourier analysis of the otoliths. Results show a significant relationship with power functions between otolith shape measurements (length, height, perimeter, area and weight) and standard length (P<0.01) in the two species. Based on the analysis of shape measurements, and compared to C. dewitti, the circularity of the otolith of Champsocephalus gunnari is lower, its shape is more circular and more regular, and it is less wide. The morphological parameters of the otoliths show a remarkable difference between the two species (P<0.01). We analyzed 77 standardized EFDs by principal component analysis (PCA); the first 20 principal components had 82.8% cumulative contribution. There was less overlap and good separation in the factor distribution picture. Six harmonics of 77 EFDs were entered in the stepwise discriminant analysis (SDA) with Fourier analysis, and the total correct classification was 92.02%. In general, otolith morphology can be used for population discrimination of these two icefish species but Fourier analysis provides more direct, clear and accurate data. The results of the present study provide basic information for otolith morphological analysis and population discrimination of these two Antarctic icefish species.

Key words: otolith morphology, Fourier analysis, Champsocephalus gunnari, Chionobathyscus dewitti