| 英文摘要 |
The production of the Pacific saury fishery from Taiwan fleets in 2006 was 60,600mt, which is smaller than the previous year’s (2005) production of 111,500mt. As to the fish stock, the CPUE in 2006 was in the range of normal fluctuation, and its production was reduced nearly to the annual average production of the last six years (64,000mt). The distribution of the fishing area in 2006 was similar to that in 2004, while the west side of the 2006 fishing area was far from the Hokkaido and the south only extended to 36oN in comparison to 2005. Means of knob lengths and body weights of the saury significantly differed among the 5 Taiwanese commercial categories, but their ranges overlapped seriously. The ranges of the saury body weights in our samples were larger than that of the standard from 5 to 38 g. The proportion of the large size in the 2006 saury catch was lager than 90 % in the beginning of the fishing season, deceased monthly, and was only 20 % at the end of the fishing season. On the contrary, the small size proportion in the 2006 catch increased monthly from 4 % in the beginning of the fishing season to 50 % at the end of the fishing season. Two normal distributions of the knob length, derived from the length frequency distribution using the Bhattacharya’s method in the model progression analysis, indicated that the knob length for age 0+ and 1+ fish ranged from 25.0-30.5 cm and 28.5-32.0 cm, respectively. The border between the age 0+ and 1+ fish length distributions was 29.6 cm. In addition, the border between the age 0+ and 1+ fish relative frequency distributions estimated by otolith determination was 29.2 cm. The theoretical asymptotic length (L∞) and growth parameter (K) of the von Bertanlanffy growth function for the saury was estimated as 34.44 cm and 0.41, respectively, if t0 = 0. At the temperature of 15℃, the total mortality coefficient (Z), natural mortality coefficient (M) and fishing mortality coefficient (F) was 1.45, 0.722 and 0.728, respectively, estimated from the length-converted catch curve. Also, population structure of the saury was re-established and the fishing mortality on the knob length was examined using the length-structured VPA in this study. |