Marine landings in Portugal have decreased at a higher rate than fishing effort in the last 20 years. Identifying the variables driving the quantity and composition of landings is pivotal to understand the dynamics of the fisheries sector, which entails complex social and environmental aspects. In this study, we investigate the main drivers of marine fish landings in continental Portugal between 1989 and 2014. To identify common trends in time series, and quantify the importance of environmental factors, we applied a dynamic factor analysis considering four regions and three types of gear (trawling, purse-seine, and a multi-gear fishery). Our results show the importance of fishing effort as the most relevant factor driving marine landings in Portugal, both at the long and short terms. In addition, the effect of environmental factors such as the winter river discharge and the spring East Atlantic Teleconnection index should not be neglected, probably through mechanisms affecting coastal productivity. We provide a comprehensive amount of information that permits to improve our understanding of the trends of the most important commercial species in Portugal during the period of study.

中文翻译：

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自加入欧盟以来，葡萄牙海洋鱼类登陆的趋势和动因

在过去的20年中，葡萄牙的海上登陆人数下降幅度高于捕捞努力。识别驱动着陆数量和组成的变量对于理解渔业部门的动态至关重要，这需要复杂的社会和环境因素。在这项研究中，我们调查了1989年至2014年之间在葡萄牙大陆上海洋鱼类着陆的主要动因。为确定时间序列的共同趋势并量化环境因素的重要性，我们应用了考虑四个区域和三种类型的动态因素分析渔具（拖网渔船，围网渔船和多渔具渔业）。我们的结果表明，从长期和短期来看，捕鱼努力是推动葡萄牙海上登陆的最重要因素。此外，不应忽略诸如冬季河流流量和春季东大西洋遥相关指数等环境因素的影响，可能是通过影响沿海生产力的机制来实现的。我们提供全面的信息，以使我们在研究期间可以更好地了解葡萄牙最重要的商业物种的趋势。