Abiotic variables accounting for presence of the exotic rainbow trout (

Rainbow trout is an exotic fish species that has been introduced in Quebec (Canada) since 1893–1894. Despite spatially-restricted stocking for recreational fishing, the species has spread throughout the Saint Lawrence River. In this study, the relationship between rainbow trout occurrence (presence or absence) and abiotic variables (river geomorphology and climate) was examined for 91 coastal rivers throughout Eastern Quebec in order to determine which variables promote or impede the ongoing invasion process. Results revealed that rainbow trout presence in Eastern Quebec was primarily determined by geomorphological parameters. The invader’s presence was strongly related to the presence of tributaries (especially larger ones). To a lesser extent, the presence of rainbow trout was positively related to warm spring and summer temperatures and negatively related to the peak flood date occurring during the egg deposition period (May). This study proposes a parsimonious modelling approach to identify which environmental parameters favour the spreading of an invader, even when a limited dataset is available due to the incomplete invasion process

Understanding and managing fish populations: Keeping the toolbox fit for purpose

Wild fish populations are currently experiencing unprecedented pressures, which are projected to intensify in the coming decades. Developing a thorough understanding of the influences of both biotic and abiotic factors on fish populations is a salient issue in contemporary fish conservation and management. During the 50th Anniversary Symposium of The Fisheries Society of the British Isles at the University of Exeter, UK, in July 2017, scientists from diverse research backgrounds gathered to discuss key topics under the broad umbrella of ‘Understanding Fish Populations’. Below, the output of one such discussion group is detailed, focusing on tools used to investigate natural fish populations. Five main groups of approaches were identified: tagging and telemetry; molecular tools; survey tools; statistical and modelling tools; tissue analyses. The appraisal covered current challenges and potential solutions for each of these topics. In addition, three key themes were identified as applicable across all tool-based applications. These included data management, public engagement, and fisheries policy and governance. The continued innovation of tools and capacity to integrate interdisciplinary approaches into the future assessment and management of fish populations is highlighted as an important focus for the next 50 years of fisheries research