Ecosystem responses to sportfish stocking and aeration in boreal foothills lakes

在整个北美西部，自然缺乏运动鱼和非本地鲑鱼的内陆水域的放养是一项成熟的管理活动，创造了新的休闲渔业。艾伯塔省可持续资源开发协会(ASRD)和艾伯塔省保护协会(ACA)目前在全省各地储存湖泊，包括小型北方山麓湖泊。然而，在淡水生态系统中增加顶级捕食者可能会对潜在的鲑鱼竞争对手以及作为鲑鱼猎物的水生无脊椎动物和两栖动物产生重大的生态影响。这些直接影响可以反过来影响食物链的其他组成部分。然而，与之前大多数研究的环境不同，我们研究的北方山麓湖泊更具生产力，包含无脊椎动物和耐寒饲料鱼的本地种群。这些湖泊通常又小又浅，因此很容易在冬季杀死鲑鱼等大型、快速生长的鱼类。根据他们的渔业管理计划，ACA因此对一些被放养的湖泊实施了曝气计划。在其第一阶段(2005-2007年)，我们的项目应用了“控制与影响”研究设计，比较了附近的养鱼和充气、养鱼和不充气以及未放养的湖泊。由于ASRD正在研究以前未被放养的湖泊，我们可以实施“事前-事后-影响”(BACI)设计，这种设计在研究生态影响方面被公认为非常强大。在这方面，我们将通过继续评估饲料鱼种群数量，进行无脊椎动物和两栖动物种群调查，以及通过稳定同位素分析研究水质和湖泊类型的食物网，监测放牧和曝气对社区的影响。这项研究对于以尽量减少对当地生物多样性的影响的方式管理可持续休闲渔业具有重要意义。我们的研究为我们提供了一个独特的机会来监督这一放养管理计划，并为这里(以及其他地方实施放鱼)的生态社区的利益以及该地区居民和游客的娱乐利益制定战略。

Throughout western North America, the stocking of inland waters that naturally lack sportfishes with non-native trout is a well-established management activity that creates new recreational fisheries. Alberta Sustainable Resource Development (ASRD) and the Alberta Conservation Association (ACA) currently stock lakes throughout the province, including small Boreal Foothills lakes. However, adding a top-predator into a fresh water ecosystem can have significant ecological impacts on potential trout competitors, and for aquatic invertebrates and amphibians that are the prey of the trout. These direct impacts can, in turn, affect other components of the food web. Unlike settings of most previous studies, however, the Boreal Foothills lakes of our study are more productive, and contain native populations of invertebrates and hardy forage fishes. Thelakes are often small and shallow and are therefore prone to winterkill for large, fast-growing fish such as trout.  In their fisheries management plan, the ACA has therefore implemented an aeration program for some of the stocked lakes. In its first phase (2005-2007) our project applied a "Control vs. Impact" study design, comparing nearby stocked and aerated, stocked and not aerated, and unstocked lakes. As ASRD stocks lakes we are studying that were previously unstocked, we can implement a "Before-After-Control-Impact" (BACI) design that is recognized as very powerful for studying ecological impact. We will monitor community consequences of stocking and aeration in this context by continuing to assess forage-fish population sizes, performing invertebrate and amphibian population surveys, as well as studying water quality and the food-web of the lake types through stable-isotope analysis. The research is important for managing sustainable recreational fishery in ways that minimizes its impact on native biodiversity. Our study provides us a unique opportunity to monitorthis stocking management program and develop strategies for the benefit of the ecological communities here (and elsewhere fish-stocking is implemented) and for the recreational interests of the region's residents and visitors.