西南大西洋遥测阿根廷鱿渔业时空动态之研究.doc

Remotely sensed spatial dynamics of the Illex argentines fishery, Southwest Atlantic西南大西洋遙測阿根廷魷漁業時空動態之研究Claire M. Waluda , Huw J. Griffiths, Paul G. RodhouseFisheries Research 91 (2008) 196-202Reporter: 凌子雅AbstractIllex argentinus, the Argentine short-finned squid, is an important species within the Patagonian shelf ecosystem, where it supports a major multi-national fishery. The fishing fleet operating in this region is comprised of jigging vessels which attract squid using powerful incandescent lights. These fishing lights are detectable in remotely sensed satellite imagery which makes the fishery unusually amenable to a large-scale analysis of its spatial dynamics. In this paper, long-term inter-annual variability in fleet distribution and extent is examined using imagery from the Defence Meteorological Satellite Program-Operational Linescan System (DMSP-OLS) for the period 1993-2005. The fishery was found to occupy a wide area across the shelf and slope, with regions of consistent fishing activity observed on the high seas (45-47S) and to the north of the Falkland Islands (Malvinas). Distribution of the fishery over the 13-year study period was variable, with 28% of the fished area occupied in 1-2 years, and 7% of the area occupied in 12-13 years. Annual catch levels were positively associated with the extent of the area occupied by the fleet. Higher catches corresponded to the fishery occupying a wide latitudinal range, whereas lower catches were observed during 2004 and 2005 corresponding to a contraction of the fishery away from the south of its range. In years of very high catches, fishing took place along almost the entire latitudinal range of the species. Due to the intensity of fishing, changes in the distribution of the fleet can reflect shifts in the distribution of I. argentinus; this has potential for the long-term monitoring of this highly variable squid fishery.摘要阿根廷魷為巴塔哥尼亞陸棚生態系中重要之物種，亦為許多國家主要之漁獲魚種。在此區作業之漁船包含魷釣船，為一種利用強力白光吸引魷魚之漁業。而衛星遙測可以測得此種漁業之燈光影像，使我們可以利用此影像來大規模之分析阿根廷魷漁業之時空動態。本篇研究利用國防氣象衛星系統所測得之影像，檢視19932005年期間，魷釣船年間分布之長期變化。阿根廷魷漁業遍及巴塔哥尼亞陸棚以及斜坡區，而在公海(4547S)以及福克蘭群島(馬爾維納斯群島)北方之區域，每年均有此種漁業在此作業。在這13年研究期間，阿根廷魷漁業之分布是多變的，在只出現12年之作業區域就佔了全部作業區之28%，而1213年均有出現之作業區域則佔了全部作業區之7%。年間之漁獲量與漁船分布之區域範圍呈正相關。阿根廷魷漁業高漁獲量分布之緯度範圍廣泛，但在2004與2005年期間，觀察到漁業自南部開始縮減之現象。在漁獲量極高之年份中，阿根廷魷漁業沿著幾乎整個魷魚分布之緯度範圍進行作業。隨著不同之漁業捕撈強度，漁船分布之改變反映出阿根廷魷分布之逐年變動，正因如此，我們有必要長期監控此種高度變動性之魷魚漁業。Fig. 1. Distribution of fishing lights targeting Illex argentinus on the Patagonian Shelf, Southwest Atlantic, obtained from the Defence Meteorological Satellite Program-Operational Linescan System (DMSP-OLS) for the period 1993-2005. Legend indicates the number of years in which fishing took place in each 2.7 km grid square, with red areas indicating regions in which fishing occurred in all 13 years of the study period. Grey lines indicate 200 and 1000 m depth contours. Black lines indicate territorial boundaries (High seas, Argentinean EEZ (Exclusive Economic Zone), FICZ: Falkland Islands (150 mile) Interim Conservation Zone (FICZ), Falkland Islands (200 mile) Outer Conservation Zone (FOCZ).Fig. 2. Frequency of occupation (number of years that fishing occurred in each grid cell based on 27 by 27 km grid cells) of the Patagonian shelf region by the I. argentinus light-fishing fleet, 1993-2005.Fig. 3. Percentage inter-annual Bray-Curtis similarity of the geographic distribution of fishing lights of the I. argentinus fleet on the Patagonian shelf, 1993-2005.Fig. 4. Inter-annual variability in the latitudinal extent of the I. argentinus fishing fleet on the Patagonian shelf (calculated as the proportion of the maximum lit area for each 27 km latitude band; n = 90). Legend shows the percentage occupation of each latitudinal band by the fleet in each year, 1993-2005.Fig. 5. (a) Annual variability in catch (log tonnes; open circles, dashed line) and area fished (km2; closed circles, solid line) for the period 1993-2005. (b) The area occupied by the