Monitoring of non-indigenous marine species for legislative and policy goals in the UK

Globally, the ecological and socio-economic impacts of non-indigenous species (NIS) are increasingly recognised, prompting the development of international policies and legislation that aim to reduce these impacts. Monitoring programmes are required to assess compliance with legislation and progress towards management targets. However, monitoring programmes often need to fulfil the requirements of several legislative drivers, as well as adapt to changing political circumstances and environmental targets, and thereby face design and implementation challenges. In this paper, we summarise the current legislative drivers for monitoring of non-indigenous marine species and provide a review of existing monitoring in UK waters. This paper also discusses aspirations for NIS monitoring, outlines progress, and provides recommendations to address remaining gaps. While the focus is on the drivers for NIS monitoring in UK marine waters, the key messages, in particular recommendations for future improvements, are applicable on a global scale.