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To clarify the life cycles of two species of genus Pempheris around Okinawa-jima Island, age and growth were examined using sectioned otolith. Monthly changes in the appearance frequency of an opaque ring on the outer margin of the sagittal otolith indicated that ring formation occurred once a year from April to June in both species. Ages were determined based on the number of opaque rings on the sectioned otolith, and the maximum ages observed for Pempheris schwenkii and Pempheris adusta were 6 and 16 years, respectively. Females had a longer life span than males in both species. The von Bertalanffy growth equations for both species did not differ between males and females, and were calculated as follows: P. schwenkii: L = 111.2 {1 − exp [−1.53 ( t + 0.08)]}; P. adusta: L = 138.8 {1 − exp [−0.84 ( t + 0.08)]}. No differences were seen in the growth of both species until 2 years old; however, at that point, the growth of P. schwenkii stagnated, whereas P. adusta continued to grow for three years. These data show that P. adusta and P. schwenkii inhabit the same environment and have similar morphologies, but different life cycle characteristics. [ABSTRACT FROM AUTHOR]

The Pacific bluefin tuna Thunnus orientalis is a highly migratory species, some tuna exhibiting a trans-Pacific migration between the Western Pacific Ocean (WPO) to the Eastern Pacific Ocean (EPO) at the juvenile stage. To detect a signature for the eastward trans-Pacific migration, we analyzed otolith stable isotope ratios of carbon (δ13Coto) and oxygen (δ18Ooto) along the growth trajectory for 20 migrants (age 3–5 years) from the EPO and 10 residents (age 2–3 years) from the WPO. The δ18Ooto values for migrants recorded during the eastward trans-Pacific migration were higher than those for residents during the same period. The higher δ18Ooto values for migrants reflect the low water temperatures encountered during their migration. The δ13Coto values were higher in the migrants than in the residents, suggesting that the higher values of carbon isotope ratios of both dissolved inorganic carbon and the diet in the EPO are recorded in the δ13Coto profiles. Our study demonstrates that otolith isotope analyses can successfully detect trans-Pacific migration of the Pacific bluefin tuna. [ABSTRACT FROM AUTHOR]