Abstract

Switching from the traditional 40- or 44-mm diamond mesh codends to 50-mm diamond mesh (D50) or 40-mm square mesh (S40) codends is known to improve the size selection for commercial species and reduce discarding in the Mediterranean demersal trawl fisheries. This change has been recommended in the General Fisheries Commission for the Mediterranean and European Commission regulations. However, ecosystem-based assessment of improved selectivity still remains a challenge, and that is the aim of this study. For this purpose, an Ecopath model was developed and used to initialize dynamic simulations in Ecosim. The simulations changed gear-specific fishing mortality rates to represent the shifting from traditional codend to alternative codends. Our results suggest that the use of D50 or S40 codends would have a positive impact on the ecosystem as a whole and on the stock status of several commercial and non-commercial groups. Mixed trophic impact analysis indicated that, for species, like red mullet, the S40 codend was significantly better than the D50 codend. This information can be useful to policymakers, particularly for the areas where red mullet is the main target species and could inform trawl mesh options in the eastern Mediterranean.

中文翻译：

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使用生态系统建模方法评估了东地中海拖网选择性对社区的影响

摘要

从传统的40毫米或44毫米菱形网眼编码单元切换到50毫米菱形网眼（D50）或40毫米方形网眼（S40）编码域，可以改善商业物种的尺寸选择并减少地中海深海拖网的丢弃渔业。通用渔业委员会针对地中海和欧洲委员会的法规建议进行此更改。但是，基于生态系统的选择性提高评估仍然是一个挑战，这就是本研究的目的。为此，开发了Ecopath模型并将其用于初始化Ecosim中的动态仿真。模拟改变了特定于渔具的捕鱼死亡率，以代表从传统code到替代to的转变。我们的结果表明，使用D50或S40编码单元将对整个生态系统以及几个商业和非商业群体的存货状况产生积极影响。混合营养影响分析表明，对于像红鱼这样的物种，S40编码比明显优于D50编码。这些信息对决策者很有用，特别是对于以红鱼为主要目标物种的地区，并且可以为地中海东部的拖网选项提供信息。