| 英文摘要 |
(1) This study aims at quantifying the population index of Argentine squid in the South-west Atlantic. The catch dataset composed 219,579 daily operation data-points, included operational date, area, bottom depth, and water temperature during 1986-2007. The jigging fleet is put together by about 100 vessels of 700-800 t in gross tonnage. The fishing efforts were first standardized intra-annually due to different catchability among the vessels, and subsequently adjusted cpue's were obtained annually. Inter-annual difference among year were quantified by generalized linear modeling (GLM), in which analysis cpue is responsible variable and year, fortnight period and water temperature are explain variables. We take the modeled yearly values as relative abundance size (abundance index) for the year in question. The result exhibited that input of fishing effort was independent from squid abundance, while catch size was positively releted to the abunadnce index. Catches of 2007 were much higher than past 5 years, but the fishing ground was apparent not wider than previous years, because high density of squid was concentrated at Southern Patagonia Shelf margin. The area with CPUE value greater than 40 d-1 v-1 could be found at least 9 units of 0.5 x 0.5 degree square. In the early fishing phase (February), squid school of high abundance had already reached to shelf break at 46 oS. This school did not move onto the Shelf but straddling around the shelf break, and finally reaching to the north of the Falkland Islands. The pattern of northern migration was ordinary shown by reaching to 42 oS in April. Analysis of GLM indicated that year effect was the most significant in CPUE variations, and the second fortnight differences, while the temperature was insignificant. We found that the cause of high production in 2007 was not related to real high abundance but reduced fishing effort from Japan and Korean vessels. Despite the different scenarios between year, the GLM analysis confirm the recover of squid abundance from the low in the past fives years.
The jumbo flying squid, Dosidicus gigas, is a pelagic ommastrephid squid and distributed in the eastern Pacific ranged from 40oN to 47oS. The fishery for jumbo flying squid started in the early 1970s with annual catches less than 10,000 tons. However, annual catches reached as high as 240,610 tons in 1990~2005 period, in which Peru shared out 24.8% of total catch and Mexico 22.3%. In the same period, the catches from Taiwanese squid jiggers were averaged 22,600 tons, which accounted for 9.4% of the total catch.
(2) In this study, we converted the catch data of Taiwanese D. gigas fishery, from commercial categories in weight to mantle length (ML) composition in number, and analyzed the effect of catch and recruitment strength based on the size composition. The transition matrix was constructed based on the biological information from 330 individuals. The results showed that the large-sized group (＞40 cm ML) was the major component of catches in 2002~2007, and small-sized group (
(3) The production of the Pacific saury fishery from Taiwanese fleets in 2007 was 87 thousand mt, which is larger than the 2006 production of 61 thousand mt and the recent 5-years-mean production of 76 thousand mt. As to the fish stock, the CPUE in 2007 was at a high level but still in the range of normal fluctuation. A high CPUE area in east of Hokkaido, where one was not found in 2006, was present in 2007 and 2005. In addition, a new high CPUE area around 147oE and 40oN was found exclusively in 2007. Most means of knob lengths and body weights of saury for the 5 Taiwanese commercial categories from the one fishing vessel sampled in 2007 were between those from the two fishing vessels sampled in 2006. Proportions of the large size saury in the catch have tended to increase from 1994 to 2007. On the contrary, the medium size proportions have trended down. The small size proportions have had a tendency of slow increase. The medium size proportion was negatively and significantly correlated to the large size (r = -0.62) and small size (r = -0.82) proportions in 1994 - 2007. Three normal distributions were fitted in the knob length frequencies of saury using the Bhattacharya’s method of model progression analysis for each year of 1994 - 2007. At the habitat temperature of 15℃, the total mortality coefficient (Z), natural mortality coefficient (M) and fishing mortality coefficient (F) was 2.58, 1.94 and 0.64 in 2007, respectively, estimated from the length-converted catch curve. The exploitation rate was 24.8%. F0.1 and Fmax was estimated as 2.08 and 2.32, respectively, when minimum fishing length Lc was assumed as 22.0 cm. During the period of 1994 - 2007 the highest and lowest yearly exploitation rate was 49.2 % in 1996 and 9.8 % in 2005, respectively. The exploitation rate of saury was negatively correlated to the abundance index CPUE in these 14 years (r = -0.54). |
