PS 19-184 - Modelling distribution and abundance of young-of-the-year redhorses in the Richelieu River

Background/Question/Methods

Freshwater fishes are one of the most threatened groups of animals in North America. In Quebec, the Richelieu River hosts five Moxostoma species, two of which have been assessed by the Committee on the Status of Endangered Wildlife in Canada due to the effects of habitat degradation and loss, pollution and climate change on their populations: River Redhorse (special concern), and Copper Redhorse (endangered), which is also endemic to Quebec. The goal of our study is to evaluate the factors that influence the distribution and abundance of young-of-the-year (YOY) redhorses through space and time, to inform conservation strategies to ensure YOY survival and to protect and recover their populations. We gathered samples at fine spatial resolution along two sectors of the Richelieu River, where YOY abundance has been measured in late September for each redhorse species since 1999, along with water temperature. Given their similar habitat requirements, we used spatially and temporally constrained joint species distribution models (JSDM) to examine the factors structuring the distribution and abundance of the YOY of the five redhorse species.

Results/Conclusions

We found that YOY redhorses exhibit a preference for the west bank of the river in the Saint-Marc sector regardless of the sampling year, which could be linked to hydrological conditions as well as microhabitat characteristics. Furthermore, our results did not always show a strong correlation between temperature and abundance of YOY redhorses, however implementing time lags may prove important to determine how climate change may have an impact on YOY redhorses. Our results also indicate that JSDMs outperform single-species distribution models. This highlights the importance of including all five species in a single model, to improve predictions of future distribution, specifically for the rare copper redhorse. Using spatially and temporally constrained JSDMs offers great insights into the factors structuring YOY redhorse distribution and abundance in the Richelieu River and will help guide future conservation actions under a changing environment.