The Recruitment Process of Black Porgy Acanthopagrus schlegeli

• Main Authors: Wen-Bin Huang, 黃文彬
• Other Authors: Tai-Sheng Chiu
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/51304929278713390038

博士 === 國立臺灣大學 === 動物學研究所 === 88 === Black porgy (Acanthopagrus schlegeli) is widely distributed in the tropical-temperate western north Pacific and a valuable commercial species in many parts of Asia, particularly in Taiwan and Japan. It is one of the dominant species in the larval fish community in the coastal waters of western central Taiwan. There are two major types of topographic waters along the coast: estuaries and coastal shelf waters. The effects of maternal conditions, egg size, larval body length, meteorological and hydrological conditions, and eco-geographic difference in the coastal waters on the recruitment process of the black porgy were studied. The otolith and somatic growths of the larvae were also determined. Age-II females produced significantly larger eggs as compared to the same size of Age-III females (p < 0.05). Also, within each of the age groups, there was a positive relationship between egg size and female size. The larger eggs generally had larger volume of oil globules, required longer incubation period (hatching age), and produced larger larvae that endured longer starvation. Hatching age was covaried negatively with yolk volume at hatching, indicating that the black porgy, during embryonic development, primarily consumed yolk as its energy resource. The condition factor, gonadosomatic index, hepatosomatic index, and lipid content of the maternal parents were not related to the early life history traits of their offsprings (p  0.05). In the coastal waters of western central Taiwan, low temperature, high atmospheric pressure, and high wind speed were the main environmental variables associated with the recruitment of larval black porgy. Most of the larvae recruited from late winter to early spring. The larvae were more abundant in the coastal shelf waters than in the estuaries. The mean body length in the coastal shelf waters (9.28  0.10 mm) was greater than that in the estuary (7.33 0.32 mm), but the coefficient of variation of body length in the former (8.15  1.15%) was smaller than that in the latter (19.87  5.26%). The range and mode of the length-frequency distributions were different between the two waters. For instance in February 1993, the range of the distribution of body length in the estuary (5.0 ~ 12.5 mm) was wider than that in the coastal shelf waters (8.5 ~ 11.5 mm) but the mode of standard length in the former (6.5 mm) was smaller than that in the latter (10.0 mm). The regression of the number of growth increments in otoliths (N) on age in days after hatch (D) of reared larvae was N = 1.061 + 0.987 D (D = 0, the day the larva hatches). Both the slope and intercept of the regression were not significantly different from 1 (p  0.05), indicating that otolith growth increment was deposited on a daily schedule since hatching. At 15.0 ~ 20.5℃ (17.9 ± 0.3℃), growth of the larvae was expressed by SL = 2.35 + 0.145 D + 0.0017 D2 for the first 38 days, where SL was the standard length and D was the age in days. In reference to the growth function, the age of the black porgy larvae in the estuary ranged from 10 to 46 days old, and most of the larvae were 23 days old. By contrast, the larval age in the coastal shelf waters ranged from 29 to 42 days old, and most were 37 days old. In short, the age of the larvae in the coastal shelf waters was 14 days older than that in the estuary of western central Taiwan.