闽南-台湾浅滩渔场蓝圆鲹资源的评估

STOCK ASSESSMENT OF DECAPTERUS MARUADSI ALONG THE SOUTH-FUJIAN COAST AND TAIWAN BANK USING LENGTH COHORT ANALYSIS

以1971—1987年的蓝圆鲹叉长组成资料,应用体长股分析法评估了闽南-台湾浅滩渔场蓝圆鲹的资源。结果表明,1971—1980年的现存资源数量和生物量分别为45292×10~5尾和9.49×10~4t,1981—1987年分别为63908×10~5尾和13.51×10~4t;1971—1980年和1981—1987年的瞬时捕捞死亡率分别为0.6347和0.4859。通过Beverton-Holt模式估算出蓝圆鲹目前的持续产量为9.58×10~4t,最佳最小捕捞叉长为135mm。

The abundance and mortality of Decaptert4S maruadsi, along the South-Fujian Coast and Taiwan Bank in two periods, 1971-1980 and 1981-1987, were estimated using length cohort analysis. The annual instantaneous fishing mortality rate, standing stock size and biomass were estimated to be 0.6347, 45 292×105 in number and 94 939 t, respectively, for the first period, and 0.4859, 63 908×105 in number and 135 073 t for the second. The abundance was higher, but the fishing mortality was lower in the second period compared to the first. The increase of the abundance in the second period might have resulted from: 1) the decrease of instantaneous natural mortality rate from 0.6607 to 0.6247, 2) the decrease of annual instantaneous fishing mortality rate from 0.6347 to 0.4859, 3) the increase of the minimum fishing fork length from 37mm to 62mm.The annual fishing mortality rate, Fi had a peak located between the 201-210 mm fork length group for the first period, and a peak each in the 131-140 mm and 191-200 mm fork length groups respectively, for the second. The peak in the first period and the second peak in the second period were due to the fishing of spawning stock, and the first peak in the second period was probably due to the development of smaller fishing boats along the inshore area.The biomass curves for two periods were bell-shaped. The maximum value occured between the 161-170 mm fork length group for the first period, and the 171-180 mm fork length group for the second.The equilibrium yield was estimated to be 95800 t with the Beverton-Holt equilibrium yield model. Examination of effects of different recruit ages, tR and different annual fishing mortality rates F1 on the Decapterus maruadsi fishery showed the equilibrium yield curve pe-aced when tR was 0.6 and F1 was 1.4. The best minimum fishing fork length was then calculated to be 135 mm.