Aphanius iberus is an endemic cyprinodontoid fish species of Mediterranean ponds in danger of extinction. In this study, we studied some abiotic and biotic factors that can influence A. iberus’s size structure and density in Mediterranean brackish ponds. We sampled fish using fyke nets in 10 ponds of Emporda (Spain) during the spring season. Our results showed that a better ecological status (according to the Water Quality of Lentic and Shallow Ecosystems (QAELS) index), pond’s depth and pond’s isolation (reflected by an increase in total nitrogen) were related to larger individual sizes and more size-diverse populations. Increasing the salinity is known to help the euryhaline A. iberus acting as a refuge from competitors. Nevertheless, our results showed that higher conductivities had a negative effect on A. iberus’s size structure, leading to a decrease in the mean and maximum size of the fish. Fish abundance (expressed as captures per unit of effort (CPUE)) seemed to increase with increasing the pond’s depth and total nitrogen (the latter reflecting pond isolation). In conclusion, our results suggest that achieving a better pond ecological status may be important for the conservation of endangered A. iberus, because better size-structured populations (i.e., larger mean and average lengths) were found at higher water quality conditions.

中文翻译：

---

影响地中海咸水池塘受威胁和地方性Cyprinodont Aphanius iberus丰度和种群规模结构的因素

Aphanius iberus 是一种濒临灭绝的地中海池塘特有的鲤科鱼类。在这项研究中，我们研究了一些可以影响地中海咸水池塘中 A. iberus 大小结构和密度的非生物和生物因素。我们在春季期间在 Emporda（西班牙）的 10 个池塘中使用 fyke 网对鱼进行了采样。我们的结果表明，更好的生态状况（根据软体和浅层生态系统的水质 (QAELS) 指数）、池塘的深度和池塘的隔离（反映为总氮的增加）与个体体型更大和体型更多样化有关。人口。众所周知，增加盐度可以帮助广盐性 A. iberus 作为竞争对手的避难所。尽管如此，我们的结果表明，较高的电导率对 A. iberus 的尺寸结构有负面影响，导致鱼的平均尺寸和最大尺寸减小。鱼类丰度（表示为每单位努力的捕获量 (CPUE)）似乎随着池塘深度和总氮（后者反映池塘隔离）的增加而增加。总之，我们的结果表明，实现更好的池塘生态状态可能对保护濒危 A. iberus 很重要，因为在更高的水质条件下发现了更好的规模结构种群（即更大的平均长度和平均长度）。