Long-term fluctuations in the eastern Atlantic and Mediterranean bluefin tuna population
Long-term fluctuations in the eastern Atlantic and Mediterranean bluefin tuna population
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东大西洋和地中海蓝鳍金枪鱼种群的长期波动
DOI：
10.1006/jmsc.2001.1119
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Fromentin
中科院分区：
文献类型：
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作者：
C. Ravier;J. Fromentin
介绍并分析了地中海和大西洋诱捕蓝鳍金枪鱼渔获量的长期时间序列。诱捕器是一种被动的渔具，几个世纪以来几乎没有改进过，在蓝鳍金枪鱼每年产卵的迁徙过程中捕捉它们。这些特征，加上初步分析，使我们认为，诱捕渔获量的长期波动可以反映出真正丰富的捕捞量，如果在整个西地中海和邻近的大西洋以同样的方式变化的话。为了验证这一假设，我们调查了意大利、西西里、撒丁岛、突尼斯、西班牙和摩洛哥西地中海海岸以及邻近的西班牙、葡萄牙和摩洛哥大西洋海岸的54个长达20多年的时间序列(最长的时间序列跨越四个世纪)。用特征向量滤波和谱分析识别趋势和周期，用修正的Koenig和Knop相关图研究捕获量短期和长期波动之间的同步性。诱捕量的波动幅度很大，丰度最高的时期比丰度较低时大七倍。更有趣的是发生了长达100年的周期波动和20年的周期波动。这些中长期波动占时间序列总变异性的50%以上，在整个西地中海和邻近的北大西洋是同步的。相比之下，短期变化仅在局部范围内是同步的。有人认为，圈闭渔获量的长期波动可以被视为真实丰度的替代，并计算了一个合成的时间序列来描述它们。还讨论了可能导致这种长期波动的生物和生态过程。
Long-term time-series of bluefin tuna catches from ancestral Mediterranean and Atlantic trap fisheries are presented and analysed. The trap is a passive gear, little modified for centuries, that catches bluefin tuna Thunnus thynnus during their annual spawning migration. These features, together with preliminary analyses, lead us to suggest that long-term fluctuations in trap catches could reflect those in true abundance if they vary in the same manner all around the western Mediterranean and adjacent Atlantic. To test this hypothesis, we investigated 54 time-series more than 20 years long (the longest ones spanning four centuries) of trap catches along the western Mediterranean coasts of Italy, Sicily, Sardinia, Tunisia, Spain, and Morocco, and the adjacent Atlantic coasts of Spain, Portugal, and Morocco. Trends and cycles were identified using Eigen Vector Filtering and spectral analysis, and the synchrony between short- and long-term fluctuations in trap catches was studied with the modified correlogram of Koenig and Knops. The magnitude of fluctuations in trap catches is large, periods of great abundance being up to seven times bigger than those when abundance was low. More interesting was the occurrence of 100-year-long periodic fluctuations as well as 20-year cycles. These medium- to long-term fluctuations, representing more than 50% of the total variability in the time-series, were synchronous all around the western Mediterranean and adjacent North Atlantic. In contrast, short-term variability was synchronous at a local scale only. It is argued that long-term fluctuations in trap catches could be considered as a proxy for those of true abundance, and a synthetic time-series has been computed to depict them. Biological and ecological processes that could cause such long-term fluctuations are also discussed.