Eel recruitment and stock have been in decline since at least the mid 1980s. So far, much research has focussed on conservation objectives and estimating silver eel production in response to the EU Regulation (EC 1100/2007) and most surveys have been on waters subject to exploitation and/or stocking. The aim of this study is to examine a 35-year yellow eel survey dataset to determine relative abundance trends while accounting for survey design, and important physical and operational covariates. Chains of ten, or sometimes five, fyke nets were fished at fixed sites in four lakes on a catchment in the west of Ireland not impacted on by exploitation or stocking. Captured eels (10,474) were counted for each trap, and eel weight was recorded for each chain of nets (5515 net nights fished). Data were analysed using a generalised additive model (GAM) that included smoothed trends over time and covariates day-of-year, depth, gradient, site and net chain. Yearly trends and between-chain variability were significant for all locations with trap depth and gradient being important for some lakes. Standardised trends by number and mass declined markedly in both tidal areas − 84.7% and − 89.5% by count and − 93.5% and − 89.5% by weight; significant declines (− 39.2% by count and − 54.1% by weight) were found in one of the freshwater lakes with the other, the one farthest upstream, having had changes over time but no significant difference between the start and end. This study provides a framework for analysing long-term fyke net catch data for eel, which may be useful for the international analysis of eel survey data.

至少自 20 世纪 80 年代中期以来，鳗鱼的补充量和存量一直在下降。到目前为止，许多研究都集中在保护目标和根据欧盟法规 (EC 1100/2007) 估算银鳗产量，并且大多数调查都是针对受到开发和/或放养的水域。本研究的目的是检查 35 年的黄鳗调查数据集，以确定相对丰度趋势，同时考虑调查设计以及重要的物理和操作协变量。在爱尔兰西部一个未受开发或放养影响的集水区的四个湖泊的固定地点，用十个或有时五个网组成的网进行捕鱼。对每个陷阱捕获的鳗鱼（10,474 条）进行计数，并记录每个网链的鳗鱼重量（5515 个网夜捕捞）。使用广义加性模型（GAM）对数据进行分析，其中包括随时间推移的平滑趋势以及协变量年中的日期、深度、梯度、位点和网络链。年度趋势和链间变化对于所有位置都很重要，圈闭深度和梯度对于某些湖泊很重要。按数量和质量计算的标准化趋势在两个潮汐区均显着下降 - 按计数计算 - 84.7% 和 - 89.5%，按重量计算 - 93.5% 和 - 89.5%；其中一个淡水湖（按数量计算 - 39.2％，按重量计算 - 54.1％）发现了显着下降，而另一个淡水湖（最远的上游）随着时间的推移发生了变化，但开始和结束之间没有显着差异。这项研究为分析鳗鱼的长期 fyke 网捕捞量数据提供了一个框架，这可能有助于鳗鱼调查数据的国际分析。