Understanding how ecosystem processes influencing fish distribution operate across spatial scales is important to understand biological invasions. Salmonids, originally from the Northern Hemisphere, have been repeatedly introduced throughout the world, making them an ideal group to test hypotheses about factors driving invasions. We assessed the influence of environmental variables at the watershed scale on the abundance and structure of salmonid assemblages in the breeding streams of the Upper Limay river basin, Rio Negro, Argentina. We combined field captures with digital map data and geographic information systems to examine landscape-level patterns of salmonid abundance in 35 representative sub-basins of the environmental gradient. We employed a hierarchical cluster analysis and classification and regression tree models to relate the abundance of salmonids and types of species assemblages with environmental characteristics at watershed level. We found stream localization, precipitation regime, altitude and air temperature to be important predictors of the abundance and assemblage structure of salmonids. Total catches showed an increasing gradient of catch-per-unit-effort from west to east and from north to south, with Oncorhynchus mykiss being the most abundant species. O. mykiss relative abundance was westward skewed, where smaller catchments with steeper and shaded valleys are drained by less productive streams with more irregular hydrological regimes, like those found in this species' North American native range. In contrast, the abundance of Salmo trutta abundance was eastward skewed, where larger, sunnier and more gently sloped catchments result in more productive streams with stable hydrological regimes, like those found in that species' European native range. Thus, differential salmonid abundance could result from the interplay between the evolutionary fingerprint left by each species' native environment (especially flow and temperature regimes) and the availability of those conditions in new environments to which they have been translocated. By furthering our understanding of how landscape conditioned invasion success, these findings can help guide the management of economically important introduced fish.

中文翻译：

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调节北巴塔哥尼亚河流夏季鲑鱼分布格局的景观因素

了解影响鱼类分布的生态系统过程如何跨空间尺度运作对于了解生物入侵非常重要。鲑鱼最初来自北半球，已多次被引入世界各地，使它们成为检验有关推动入侵的因素的假设的理想群体。我们评估了流域尺度的环境变量对阿根廷里奥内格罗上利迈河流域繁殖溪流中鲑鱼组合丰度和结构的影响。我们将实地捕获与数字地图数据和地理信息系统相结合，以检查环境梯度的 35 个代表性子流域中鲑鱼丰度的景观水平模式。我们采用层次聚类分析、分类和回归树模型将鲑鱼的丰度和物种组合的类型与流域水平的环境特征联系起来。我们发现河流定位、降水状况、海拔高度和气温是鲑鱼丰度和组合结构的重要预测因子。总产量显示出从西到东和从北到南的每单位努力量的增加梯度，其中 Oncorhynchus mykiss 是最丰富的物种。O. mykiss 的相对丰度向西倾斜，其中较小的集水区与陡峭和阴凉的山谷被生产力较低的溪流排干，水文状况更不规则，例如在该物种的北美原生范围内发现的溪流。相比之下，Salmo trutta 的丰度向东倾斜，在那里更大、更阳光、更平缓倾斜的集水区导致更多产的溪流具有稳定的水文状况，就像在该物种的欧洲原生范围内发现的那样。因此，不同的鲑鱼丰度可能是由于每个物种的原生环境（特别是流量和温度状况）留下的进化指纹与它们在新环境中易位的条件之间的相互作用造成的。通过进一步了解景观如何影响入侵的成功，这些发现可以帮助指导具有重要经济意义的引进鱼类的管理。就像在该物种的欧洲本土范围内发现的那些一样。因此，不同的鲑鱼丰度可能是由于每个物种的原生环境（特别是流量和温度状况）留下的进化指纹与它们在新环境中易位的条件之间的相互作用造成的。通过进一步了解景观如何影响入侵的成功，这些发现可以帮助指导具有重要经济意义的引进鱼类的管理。就像在该物种的欧洲本土范围内发现的那些一样。因此，不同的鲑鱼丰度可能是由于每个物种的原生环境（特别是流量和温度状况）留下的进化指纹与它们在新环境中易位的条件之间的相互作用造成的。通过进一步了解景观如何影响入侵的成功，这些发现可以帮助指导具有重要经济意义的引进鱼类的管理。原生环境（尤其是流量和温度状态）以及这些条件在它们已转移到的新环境中的可用性。通过进一步了解景观如何影响入侵的成功，这些发现可以帮助指导具有重要经济意义的引进鱼类的管理。原生环境（尤其是流量和温度状态）以及这些条件在它们已转移到的新环境中的可用性。通过进一步了解景观如何影响入侵的成功，这些发现可以帮助指导具有重要经济意义的引进鱼类的管理。