Daily age and growth of juvenile grey mullets Mugil cephalus in the Tan-Shui River Estuary as revealed from otolith microstructure.

• Main Authors: CHANG, CHIN-WEI, 張至維
• Other Authors: WANN-NIAN TZENG, YING-CHOU LEE
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/77830933361758912813

碩士 === 國立臺灣大學 === 漁業科學研究所 === 85 === Grey mullets Mugil cephalus are not only important coastal or inshore species but also very desirable aquaculture species in Taiwan. Adults migrate to the southwestern coasts of Taiwan for spawning during late November through the following late January. However juveniles are captured from early November in the coastal estuaries. These phenomena indicate the disagreement in the period between adults spawning and juveniles occurrence. For understanding the disagreement, the periodicity of daily growth increments deposited in otoliths of juvenile grey mullets was validated by using tetracycline immersion. Then, daily age and growth of the juveniles collected in the Tan - Shui River Estuary during the periods from November 1995 through March 1996 and from November 1996 through March 1997 were determined by growth increments in otoliths. Spawning period of the juvenile grey mullets was backcalculated from their daily age. Except the daily growth increments, several remarkable checks like sub - daily growth increments, accessory primordia, secondary growth zones and first feeding check were found in the otoliths. The juvenile grey mullets arrived the estuary at the size of 20.56 mm mean TL (approximately 32 days after hatching), left the estuary at 34.00 mm (62 days). The duration of estuarine staying was about a month, growth rate was 0.452 mm d-1 during this period. The juveniles in the estuary were composed of multiple cohorts. Backcalculated spawning period lasted approximately five months from October through the following February. This indicated that the juveniles collected in the Tan - Shui River Estuary were not completely originated from the migratory spawning stock in the coastal waters off southwestern Taiwan.