| Electron Antarctic Electrona Antarctica was the most representative mesopelagic fishes in Antarctic. The parameters of age and growth were the significant reference of stock assessment, the selection of ageing method was the basis to conduct age and growth of fish. The study conclude the relationship of age and growth and the accuracy of age determination, after finished the measurement of morphological parameters of otolith and the analysis and research of annulation on the section. The study provided the basic information and data for future research.The morphological parameters of 100 sagittal otoliths were measured and analyzed based on Electron antarctic(Electrona antarctica) samples(standard length 72.67 to 91.81 mm) collected from the South Shetland Islands from December 2012 to February 2013. In the end, the study got 74 rigth otoliths with clear annulation. The study showed as follows:(1) Compare to its size, the otolith of Electrona antarctic is large, the length is close to the width of otolith. The excisural notch and the sulcus of the otolith are clear. The length of rostrum and the antirostrum are close, although they are not obvious. The length of left(right) otolith range from 3.00 to 3.81 mm(2.99 to 3.72 mm) respectively, and the width of left(right) otolith range from 2.98 to 3.62 mm(3.05 to 3.67 mm) respectively.(2) The width and circumference of otolith show stable variation with the growth of fish, however the variation on rostrum and the antirostrum of otolith are remarkable varies for all otolith morphological parameters. The acreage of otolith is the most stable parameter and shows the higher relationship to the standard length of fish, the growth of otolith’s total length is more stable than that of otolith width.(3) A significant difference can be found for width and circumference between the left and right otoliths, but unremarkable differences are showed for total length, acreage, the distance between excisural notch to margin along sulcus and length of rostrum between the left and right otoliths.(4) After the AIC fitting model test, the study showed that the relationship between the standard length and the length of otolith, the width of otolith, the area, the perimeter was:left: SL= 49.799e0.1432 L2(R2 = 0.3695),SL= 57.306ln(L3) + 13.02( R2 = 0.5005),SL= 29.316ln(C1) + 20.913(R2 = 0.5341),SL= 56.493ln(P1)- 51.202(R2 = 0.4678)right: SL= 48.147e0.1516L2(R2 = 0.3812),SL= 16.101L3 + 28.097(R2 = 0.4307),SL= 3.1612C1+ 55.927(R2 = 0.3463),SL= 63.161ln(P1)- 67.673(R2 = 0.4711).(5)After the AIC fitting model test, the study showed that the weight of the otolith showed high relationship to the standard length of otolith. The relationship as follows:left:SL = 2.0961 Wo + 63.773(R2 = 0.4335)WW = 3.0877e0.0997Wo(R2 = 0.5382)right:SL = 0.3416Wo2- 4.2002 Wo + 92.298(R2 = 0.4307)WW = 0.142Wo2- 1.8217 Wo + 12.347(R2 = 0.5869)(6)The sulcus of otolith was a serious of tight annulation which from core to excisural notch, while the core is a round sphere which was embedded as to be a trigon. And the otolith trend to growth follow dorsal side.(7) The otoliths were cut transversely to ensure that the primordiums of the otoliths were aligned. The section consisted of long arm and short arm, and the short arm provided the most reliable age estimate. Sections were observed under transmitted white light microscope using the same magnification for all otoliths, regular rings can be observed. After three one’s reading, the age was determined by the average.(8)The length and weight, circumference and acreage of otolith showed high relationship to the standard length, which was WW =2.5086*10-5FL2.8586(R2 = 0.7187).(9)With the formula of CV and APE, the total percent of agreement(TC), the average percent error(APE) and coefficient of variation(CV) were 57.3%, 2.83% and 3.8% respectively. The otolith could be used to age determination of Electrona antarctic.(10)The average age of the sample of Electrona antarctic was 5.5. The age ofElectrona antarctic showed logarithmic relationship to the standard length, which was:SL= 20.705ln(t) + 47.184(R2 = 0.2982)(11)The range(70mm-90mm) of the sample was too narrow to fitting the growth model.Among the formula :Lt=L∞=(1-e-k(t- t0)),L∞=84.41188,k=2.4368,t0=3.746767... |
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