What Factors Structure Lake Sturgeon Spawning Aggregations in a Great Lakes Connecting Channel?

Uncertainty in demographic rates and life history parameters can inhibit effective ecological inference of animal populations. Such uncertainty may be expected for many rare or recovering species, but dynamics can be rendered even more opaque if these species also exhibit complex life cycles. Lake Sturgeon (Acipenser fulvescens) live long, mature late, and migrate, which can hamper short term monitoring efforts. In the lower Niagara River, large aggregations of these fish have been found annually, and are typically comprised by a mix of reproductively active and inactive adults or sub-adults. We asked whether variation in spring aggregation densities during the spawning season was more dependent on environmental conditions or population demographics. However, we expected that high uncertainty in our population monitoring data would need to be accommodated in our analytical framework. We first built a demographic population model from information in the literature, and then used this as prior information in a multi-study integrated population model estimated from data collected in our system. We compared competing model parameterizations with and without available abiotic variables using an information theoretic approach to test whether abiotic or population demographic factors affected Lake Sturgeon aggregation size in the lower Niagara River during our monitoring efforts.