Age, growth and migratory environmental history of southern bluefin tuna (Thunnus maccoyii) in the Indian Ocean
Date Issued
2006
Date
2006
Author(s)
Lin, Yu-Ting
DOI
zh-TW
Abstract
Southern bluefin tuna (SBT, Thunnus maccoyii) is a large, oceanic migratory fish. It is found throughout the southern hemisphere mainly in waters between 30 and 50 degrees. The only known spawning area is in the Indian Ocean southeast of Java, Indonesia. To understand the growth and migratory environmental history, this study used the SBT otolith to determine the age and analyze the trace element in otoliths. In 2003 and 2004 a total of 418 otoliths were collected from the SBT caught by Taiwanese longliners in the central Indian Ocean (29-33°S, 67-91°E) .Their fork length ranged from 87-177 cm and ages were between 2-22 years old. In addition, a total of 197 otoliths were collected from the SBT caught in the spawning ground (10-20°S, 110-120°E) by an Indonesian observer in January and February 2005. Fork length of the SBT ranged from 152-205 cm and ages were between 11-26 years old. The samples collected from Indonesia were sexually matured spawning individuals. The length-weight relationship and growth curve of SBT was significantly different between female and male. Before the age of sexual maturity in approximately 10 years old, female grew faster than male, but male had the larger asymptotic length. The growth parameters of the von Bertalanffy growth equation were estimated to be t0=-5.1047 yrs, K=0.0997 yr-1, and L∞=190.06 cm, using all regional and sexual data. The catch of Taiwanese SBT fishery was mainly composed of 2 to 10 years old, accounted for about 95% of the total catch. The SBT caught by Taiwanese fishery was skewed to young individuals based on the facts that the life span of SBT was approximately 40 years old, and the age at maturity was around 10 years old.
This study used otolith microchemistry as a natural tag to retrieve the past migratory environmental history and larval origin of the SBT in the Indian Ocean. The otolith compositions were measured via solution-based (SB) inductively coupled plasma mass spectrometer (ICPMS), and laser ablation (LA) ICPMS. The result of SB-ICPMS showed that the otolith elemental compositions were significantly different between age groups. This indicates that SBT migrated through different environment with growth. The result of LA-ICPMS analysis indicated that the elemental composition in the otolith edge was different between the adult fish collected from central Indian Ocean and Bali Island, but the elemental composition in the core region of the otolith that corresponding to their larval and juvenile stages were similar, irrespective of the collecting locations. This supported that the SBT was a single population in the Indian Ocean.
Subjects
南方黑鮪(Thunnus maccoyii)
性別
年齡
成長
耳石微量元素
洄游環境
族群結構
Southern bluefin tuna (Thunnus maccoyii)
sex
age
growth
otolith trace elemental composition
migratory environment
population structure
SDGs
Type
other
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