Characterising drivers of non-native fish establishment and predicting their impact on aquatic biodiversity

从理论上讲，在任何环境中引入一对有性繁殖的动物（繁殖体）应该足以使一个可持续的种群发展——这一过程被称为建立。然而，这种情况在现实中很少发生，为了建立关系，经常需要大量的重复介绍。虽然许多物种被引入外来环境，但只有少数物种发展成种群，更少的物种成为入侵物种。一个主要原因是由于环境和生物因素的限制而无法建立。繁殖体压力可能有助于引进物种克服这些限制因素，因为一些研究表明，随着繁殖体的释放和引进尝试的次数以及引进的速度，建立的可能性可能会增加。然而，如何传播数和引进率相互作用和影响建立并不明显。此外，对于一个物种来说，繁殖体的释放必须与足够的资源可用性相吻合，即繁殖体压力和资源可用性之间的相互作用可能是最关键的。虽然本地物种对资源的抢占产生了对入侵的生物抗性，但繁殖压力可能有潜力克服这一点。在原地研究生物入侵时，一个主要的限制是繁殖体压力的数据通常是缺乏的，特别是当生态学家通常不愿意故意引入新物种进行研究时。这导致对繁殖压力和建立成功之间的关系（包括引进和入侵之间的时间间隔以及生态影响）缺乏科学理解。然而，了解引进物种的特征如何影响其建立和入侵过程，对于提高对如何更好地管理引进物种的认识至关重要。这在生态学上意义重大，因为入侵物种对生物多样性的威胁仅次于栖息地丧失。尽管它们的影响被描述为巨大的，潜在的，通常是不可逆转的，但越来越多的生态学家质疑非本地物种实际上是本地生物多样性下降的直接原因的证据，并建议有必要进一步的工作来量化这一点。一种准确量化建设驱动因素和由此产生的生态影响的方法是在野外进行大规模实验。迄今为止，已经确定繁殖体压力对建立成功的影响的少数研究主要是对引进鸟类的观察性研究，很少有完整的实验方法。我们对其他脊椎动物物种知之甚少，对水生动物更是一无所知。这主要是由于将非本地物种引入新环境进行研究的主要伦理问题。然而，该项目提供了一个独特的机会，通过在一个已经拥有模式物种的河流集水区使用一个商业退役的、经许可的84个池塘的水产养殖场，使它们能够在不引入的情况下使用，来解决水生入侵生态学方面的这些知识空白。因此，通过对一种引进模式脊椎动物（上嘴鲟，伪嘴鲟）的受控实验研究，研究的目的是：1)确定引进鱼类建立率和成功的驱动因素；2)确定建筑对当地社区的生态影响；3)根据初始引进的特点，建立预测建立和影响的模型。产出将包括制定对入侵成功至关重要的过程的预测模型，可用于支持英国及其他地区目前的外来物种预防、补救和缓解技术。

Theoretically, the introduction into any environment of a pair of sexually reproducing animals (propagules) should be sufficient to enable a sustainable population to develop - a process known as establishment. However, this is rarely the case in reality and a high number of repeated introductions are often necessary for establishment. Whilst many species are introduced into alien environments, only a few develop populations and even fewer become invasive. A primary reason is the failure to establish due to limiting environmental and biological factors. Propagule pressure may assist introduced species overcome these limiting factors, as some studies have suggested that probability of establishment may increase with the number of propagules released and the number of introduction attempts, and with the rate of introduction. How propagule number and introduction rate interact and influence establishment is, however, not apparent. Moreover, for a species to survive introduction, the release of propagules must coincide with adequate resource availability, i.e. it is the interactions between propagule pressure and resource availability that may be most crucial. Although the pre-emption of resources by native species generates biotic resistance to invasion, propagule pressure may have the potential to overcome this. A major limitation when studying biological invasion in situ is that data on propagule pressure is generally absent, particularly as ecologists are generally unwilling to deliberately introduce new species for research. This has lead to a poor scientific understanding of the relationship between propagule pressure and establishment success, including the duration of the time between introduction and invasion, and ecological impacts. Yet understanding how the characteristics of introductions shape the establishment and invasion process is critical to increasing understanding on how introductions may be better managed. This is ecologically significant as the threat of invasive species to biodiversity is second only to habitat loss. Although their impacts have been described as immense, insidious and usually irreversible, there is a growing minority of ecologists who question the evidence that non-native species are actually a direct cause of declines in native biodiversity and suggest further work is necessary to quantify this. One way to accurately quantify drivers of establishment and resulting ecological impacts is through large-scale experimentation in the wild. To date, the few studies where the effects of propagule pressure on establishment success have been identified have mainly been observational studies on introduced birds, with few completed experimental approaches. Little is known about other vertebrate species, and virtually nothing about those in the aquatic environment. This is mainly due to major ethical concerns about introducing non-native species into novel environments for research. This project, however, presents a unique opportunity to address these knowledge gaps in aquatic invasion ecology through the use of a commercially decommissioned, licensed aquaculture site of 84 ponds within a river catchment that already hosts the model species, enabling their use without introduction. Thus, through the study of an introduced model vertebrate species (topmouth gudgeon, Pseudorasbora parva) into a controlled experimental setting, the objectives of the research are to: 1) determine the drivers of establishment rate and success of introduced fish; 2) identify the ecological impacts of establishment on native communities; and 3) develop models that predict establishment and impact from the characteristics of the initial introduction. Outputs will include the production of predictive models of processes essential to invasion success that can be used to underpin current preventative, remediation and mitigation techniques of alien species in the UK and beyond.