Studies On Otolith Morphology In Larval-young Silver Carp, Big Head, And Grass Carp With The Application In Species Discrimination

This papers studies early period otolith's morphological development of silver carp, big head carp and grass carp and establishes species discriminant formule based on sagitta and lapillus shape variablesthe at ages, development stages, and different body length groups by Fourier shape analysis. The main results are as following:1. The morphological development of otolith. The otolith shapes of silver carp,big head and grass carp develop similarly with sagitta from round-shape, oval-shape, rhombic-shape to sagittal-shape; lapillus from round-shape, bean-shape, long-bean-shape to wedge-shape; asteriscus from slim-shape, oval-shape, round-similar-shape to star-shape.2. Estabishment of discriminant formule on ages. When the ages are divided into six morphology stages ,the discriminant success auove oval-shape stage(11d~13d) of sagitta is over 90.23% and the test success is over 80.00%; discriminant success above bean-shape stage(12d~14d) of lapillus is over 80.08% and the test success is over 72.13%.3. Establishment of discriminant formule on development stages. In five stages from one chamber air bladder stage to formation of fins stage ,the discriminant success are 63.51%, 63.22%, 75.31%, 91.92% and 98.44% respectively by sagitta; the discriminant success are 84.78%, 70.81%, 78.47%, 82.39%, 96.03% and 98.01% respectively by lapillus.4. Estabishment of discriminant formule on body length. Discriminatedby sagitta, body length can be divided into 5 following groups: 0.86cm~ 0.90cm, 0.90cm~ 1.00cm, 1.00cm~ 1.20cm, 1.20cm~ 1.45cm and 1.45cm~ 2.15cm; the discriminant success are 90.65%, 90.44%, 97.82%, 96.45% and 98.38%.The above results show that it is reasonable to discriminate larval and young fish with its otolith by Fourier shape analysis, especially based on body length.