Abstract

Data on the demography and reproduction of marine species provide important information for a sustainable fisheries management. We show that the size at onset of maturity in female Nephrops norvegicus has been in decline for over 20 years and has always been above the established minimum landing size (MLS) in the Western Irish Sea. Determining the size at onset of maturity is one important factor to inform an effective MLS, such that individuals can reproduce at least once. The length at which half of females are sexually mature (L₅₀) in the overall population declined by over 12% in two decades, from 23.6 mm in 1997 to 20.6 mm in 2016, while the MLS has remained at 20 mm. While L₅₀ values differ among permanent sampling stations, the decline was observed at all stations. Current practice thus allows immature females to be landed before they reproduce and contribute to recruitment. While it is not always possible to identify the determining factors that drive the decline in SOM, we argue that it is appropriate to recognize this as an indicator of declining system productivity.

中文翻译：

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在长期调查中，Nephrops norvegicus的成年女性体型下降（1997–2016）

摘要

有关海洋物种的人口统计资料和繁殖数据为可持续渔业管理提供了重要信息。我们显示，雌性Nephrops norvegicus的成年期大小已经下降了20多年，并且一直高于西爱尔兰海中已建立的最小着陆大小（MLS）。确定成熟开始时的大小是告知有效MLS的重要因素之一，因此个体至少可以繁殖一次。在整个人口中，一半女性的性成熟长度（L ₅₀）在过去的20年中下降了12％以上，从1997年的23.6毫米下降到2016年的20.6毫米，而MLS保持在20毫米。而L ₅₀永久性采样站之间的数值有所不同，所有采样站均出现下降。因此，目前的做法允许未成熟的雌性在繁殖和招募前着陆。尽管并非总是能够确定导致SOM下降的决定因素，但我们认为将其视为降低系统生产率的指标是适当的。