Abstract
Sebastes schlegeli Hilgendorf is a viviparous scorpaenid fish distributed around Japan.The larvae and juveniles of this fish were reared for 80 days to clarify their development, relative growth, and mouth size in relation to feeding capability and changes in behavior.
The development of this fish can be devided into eight stages as shown in Fig.2.The just spawned larvae were 6.89 mm on average in total length.Individuals of 9.5 11.7 mm are regarded to have attained to the juvenile stage, when all the fin rays were brought to completion.The fish reached 30 mm in total length in about 50 70 days.
The growth of seven body parts (post-anal length, ante-anal length, head length, trunk length, eye diameter, auditory vesicle diameter, and mouth size) was examined against changes of total length.The growth inflection of each body part occurred at the size of 9.1-12.9 mm in total length, and coincides with the shift period from the larva to juvenile stage or just after this period (Figs.4 and 5).The mouth size and trunk length demonstrated common change showing tachyauxesis before growth inflection and isauxesis after it.
The size of food taken is determined by the mouth size.As the results, it is esti-mated that the mouth size of newborn larvae is 836 μ, and the food less than 423-629 μ can be taken easily by these larvae.The mouth size can be roughly estimated by the measurement of the trunk length.
