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A comparison of back‐calculated lengths of silver carp derived from bony structures
Author(s) -
Johdal M. S.,
Esmaeili H. R.,
Tandon K. K.
Publication year - 2001
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.2001.tb00213.x
Subject(s) - length scale , radius , biology , bond length , anatomy , fish <actinopterygii> , geometry , mathematics , zoology , physics , crystallography , chemistry , fishery , mechanics , computer security , computer science , crystal structure
Linear relationships were found between body length–scale radius, body length‐cleithrum length and body length‐urohyal length ( r =0·949, 0·984 and 0·974 respectively) in silver carp Hypophthalmichthys molitrix. Out of 180 comparisons, which were made between different methods of back‐calculating length and ageing structures at ages 2‐7 years, the differences were not significant ( P ≥ 0·05) in 132 (73·3%) cases. There were no significant differences among different methods in older age classes and between the Fraser‐Lee method and body proportional method (BPH) at all ages. The results demonstrated that in all structures, back‐calculated lengths estimated by the scale proportional hypotheses (SPH) were less than the other methods. For scales, SPH was similar to the direct proportional method of Dahl‐Lea (DPM) but for cleithra and urohyal bones it was similar to BPH and Fraser‐Lee. As the fish increased in age, the differences between back‐calculated lengths decreased. When lengths were back‐calculated using cleithra and urohyal bones, differences between the structures at age 2 years were 17 mm from DPM, 33 mm from SPH, 37 mm from BPH and 37 mm from Fraser‐Lee, while at age 8 years mean differences were 7 mm from DPM and 8 mm from the SPH, BPH and Fraser‐Lee methods. It is suggested that the differences would be less if: (1) back‐calculated lengths are based on a large number of random samples; (2) measurements of scale radius, cleithrum length and urohyal length were precise; (3) determination of focus or origin were precise; (4) the sampling of scales were from the same row.