Otolith morphology of ruby snapper Etelis coruscans in the northwestern Indian Ocean

LIN Dong-ming;XU Liu-xiong;YE Xu-chang;WANG Xue-fang;ZHU Guo-ping;College of Marine Sciences,Shanghai Ocean University;Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources,Ministry of Education;

Etelis coruscans;;otolith;;morphological analysis;;Saya de Malha bank;;northwestern Indian Ocean

The weight and morphological characters of sagittal otoliths including otolith length( OTL),otolith width( OW),otolith dorsal length( ODL),otolith dorsal width( DH),ventral length( VRL),and dorsal length( DRL)were measured in the 208 specimens of ruby snapper Etelis coruscans( fork length 383- 866 mm) collected from Saya de Malha bank in the northwestern Indian Ocean by bottom fisheries resources survey from October 2005 to January 2006. The left sagittal otolith was used in this study because there was no significant difference in otolith weight and morphology in pairs by t- test. The sagittal otolith is ovate in shape with a notch in the anterior,sulcus over the convexity,flat in the concave mesial surface,irregular dorsal margin and ventral margin,rostrum broad and antirostrum small,and had length of 9. 85- 20. 76 mm and width of 5. 03- 10. 88 mm. The significant changes in otolith length indices including OTL,ODL,and VRL and no significant changes in the otolith width indices including OW and DH were observed in the ruby snapper with fork length( FL) of less than 540 mm. In the ruby snapper with FL of larger than 540 mm,however,the unstable relative change in otolith length indices was,and stable relative change in the otolith width indices was found. There was more stable growth in OW than in OTL,and the power function was best used to describe the relationship between OW and otolith weight( R2= 0. 7790),and there was a linear relationship between OW and FL,indicating the OW is suggested to be considered as the representative character for understanding of the relationships of otolith morphological characters with otolith weight and FL.