Estimating spawning Green Sturgeon (Acipenser medirostris Ayres, 1854) abundance using side scan sonar and N-mixture models

We investigated the use of side scan sonar and N-mixture models to improve the population estimate of the threatened southern distinct population segment of the North American Green Sturgeon (Acipenser medirostris). For three years from 2020 to 2022, we collected images of all known Green Sturgeon aggregations using a Humminbird model Helix 10 with a transducer transmitting at 1.2 megahertz, while simultaneously collecting data with a DIDSON or ARIS sonar. We compared a traditional plot sampling density estimator using the DIDSON and ARIS sonar data to an N-mixture model using side scan sonar images. We investigated the use of a number of different N-mixture model distributions including Binomial and Beta-Binomial for the observation process and Poisson, Negative Binomial and their zero inflated variants for the ecological abundance process as well as the use of covariates to explain the detection process. None of these standard models were either suitable for stable enough in the param..., We surveyed potential adult Green Sturgeon aggregations (pools greater than 5m depth) in the upper reaches of the Sacramento River (Figure 1) from June 01-05 in 2020, June 07-18 in 2021 and July 18-21 in 2022. In 2020–2021, we surveyed with both a DIDSON or ARIS and SSS but only used the SSS in 2022. For each year we started at ~RMM 200 (322 km) and surveyed up to RMM 280 (450.5 km), 270 (434.5 km), and 296 (476.5 km) for a total of 32, 38, and 69 pools for the three years, 2020-22 respectively. In 2020-2021 we performed 7 passes with the DIDSON and then 3 passes with the SSS, because of COVID restrictions, only sites that had detected sturgeon at least once in the last 5 years were surveyed. In 2022, we performed 3 passes with the SSS and then up to 4 more if any fish were seen during the first 3 passes, as more passes may provide for better statistical results in sparse data sets (Hostetter et al., 2019). With the rare exception of two especially turbulent sections (one in which we re..., Text files, any standard text editor should be able to open them.