The Application Of Fourier Analysis In The Research Of Otolith Morphology

In addition, otoliths are widely used as indicators of fish age and growth at annually, daily and seasonal levels. Recent developments in the tools used for determining otolith's microconstituents have opened up possibilities of studying migrations and stock identity as well as using isotopes to reconstruct past life history of fishes, some good progress has made.The otolith form is species and group specific with the important value for fish taxonomy and systematics research, and some researchers have carried out the massive basic research in the field in recent years. Based on ten thousand otoliths collected from the recent research programms such as "908" special project of State Oceanic Administration of People's Republic of China, National Basic Research Program of China (973 program) (No.2005CB422306), etc., by bio-image analysis software and the mathematical means of Fourier analysis, some fields of fish otolith morphology:Otolith morphological characteristics and measurement methods, otolith morphological diversity, species and stocks identification, morphological changes of otolith growth were carried out. The main findings were as follows:(1)Based on otolith position and posture in the inner ear, in order to facilitate description of the otolith, we call the direction of the head as anterior, the direction of the tail as posterior, the direction of the back as dorsal, the direction of the belly as ventral. In the meanwhile, we give the distinction of the lateral and mesial surface of otolith. Rostrum and antirostrum are created by a nick in the anterior otolith region. Sulcus acusticus exists at mesial surface of otolith.Otoliths collected from 255 Species, belonging to 83 families and 13orders of fishes from China Sea were descripted. Most species were from Perciformes, others were from Clupeiformes, Anguilliformes, Myctophiformes, Siluriformes, Gadiformes, Beloniformes, Mugiliformes, Scorpaeniformes, Elopiformes, Beloniformes, and Pleuronectiformes, etc. Otolith shape, size, smoothness degree, sulcus acusticus, rostrum and antirostrum were descirpted in detail; and some measurement characteristic including otolith length, otolith width, perimeter, area, circularity, rectangularity and compactness were analyzed, the outline of the otolith was descriped by Fourier analysis. Used these shape variables into statistical analysis to identity fish.Cluster analysis and classify analysis showed that, the relatives relationship among fishes based on otolith morphology was not entirely overlap with the traditional classification system of fishes. The classification accuracy of family was 44.71%, and we suspected that family was not suitable for identification; the classification accuracy of genus and species were 81.96% and 86.44%, which showed application perspectives.(2) Otolith shape is species specific and is an ideal marker of fish population affiliation. Otolith shape of spottedtail goby Synechogobius ommaturus was used to identify stocks in different spawning locations in the Yellow Sea. o explore the potential existence of local stocks of spottedtail goby in the Yellow Sea by analysis of otolith shape, and to investigate the ambient impacts on otolith shape. Spottedtail goby was sampled in five locations in the Yellow Sea in 2007 and 2008. Otolith was described using variables correlated to size (otolith area, perimeter, length, width, and weight) and shape (rectangularity, circularity, and 20 Fourier harmonics). Only standardized otolith variables were used so that the effect of otolith size on the shape variables could be eliminated. There was no significant difference among variables of sex, year and side (left and right). However, the otolith shapes of the spring stocks and the autumn stocks significantly differed. Otolith shape differences were greater among locations than between years. Correct classification rate of spottedtail goby with the otolith shape at different sampling locations ranged 29.7%-77.4%.(3) 161 samples of Trumpeter sillago, Sillago maculata and 164 of Silver sillago, Sillago maculata were collected from Beibu gulf in july 2009. Using morphological variables and Fourier harmonics to describe otolith characteristic and use discriminant analyses to separate two species. Otoliths were measured by traditional one and two dimensional measures (otoliht length, width, diameters, area, perimeter, circularity and rectangularity), as well as by Fourier analysis to capture the finer regions of otolith. Analysis of covariance (ANCOVA) showed that there was significant correlation between morphological variables (diameter, perimeter, otolith length, otolith width, otolith area, density, harmonics3, harmonics4, harmonics5, harmonics13, harmonics15, and harmonicsl6) and body length. To minimize size effects on the shape variables between species only fish of a medium to all length (90-140 mm) were included in the data analysis and the variables which has significant relation with body length were transformed using residual. The result shows that:the discriminant analysis accuracy of Trumpeter sillago and Silver sillago were 97.8% and 100%, the high accuracy of discriminant analyses show that otolith shape was described accurately by morphological variables and Fourier harmonics, discriminant analyses is an effective way to identify and separate species.(4)Morphological characters of the sagittal otoliths were analyzed for the eight species of genus Apogon inhabiting China Sea.The results showed that the sagittae of the eight species was similar in shape, all had narrow anterior part, wide posterior part, zigzag dorsal side and arcuate ventral side with a notch in the middle of the dorsal side. The sulcus was wide. Otoliths had aspect ratio of 1.35～1.63, rectangularity of 0.67 to 0.77 and circularity of 14.77～24.99 for eight fishes. According to the sulcus acusticus shape and otolith form, a systemic taxonomy was designed for eight fishes. The results indicted that the sulcus acusticus shape is one of the important characters of otoliths morphological classification, otoliths morphology have a good prospect of application in fish systematic.(5) Morphological characters of the sagittal otoliths were analyzed for the twelve species of genus Epinephelus inhabiting China Sea.The results showed that the sagittae of the twelve species was similar in shape, all had narrow anterior part, wide posterior part, zigzag dorsal side and arcuate ventral side with a notch in the middle of the dorsal side. The sulcus was wide. Otoliths had aspect ratio of 1.35～1.63, rectangularity of 0.67 to 0.77 and circularity of 14.77～24.99 for eight fishes. According to the sulcus acusticus shape and otolith form, a systemic taxonomy was designed for eight fishes. The results indicted that the sulcus acusticus shape is one of the important characters of otoliths morphological classification, otoliths morphology have a good prospect of application in fish systematic.