Abstract
There has been considerable debate about effects of entrainment of endangered Delta Smelt (Hypomesus transpacificus) at water export facilities located in the Sacramento–San Joaquin River Delta. In this paper we use a behavior-driven movement model (BMM) to simulate the movement of adult Delta Smelt, which, in conjunction with a population dynamics model, estimates the proportion of the population that is lost to entrainment, i.e., proportional entrainment loss (PEL). Parameters of the population model are estimated by maximum likelihood by comparing predictions to data from Fall Midwater Trawl (FMWT) and Spring Kodiak Trawl (SKT) surveys, as well as to daily salvage estimates. Our objectives are to evaluate different movement behavior hypotheses, to rank estimates of PEL based on how well predictions fit the data, and to sharpen our understanding of the data to inform future research and monitoring decisions. We applied the modeling framework to data from water year 2002—a year when salvage was high—and tested 30 combinations of six behavior and five population dynamics models. More complex process and observation assumptions in the population model led to much improved fits in most cases, but did not appreciably influence PEL predictions, which were largely determined by movement predictions from the BMMs. Estimates of PEL varied considerably among behaviors (2% to 40%). The model with the highest predictive capability explained 98% of the variation in FMWT data across regions, 70% of the variation in SKT data across regions and surveys, and 28% and 43% of the daily variation in salvage at federal and state fish screening facilities, respectively. The PEL estimate from this model was 35%, more than double the original estimate from Kimmerer (2008) of 15%. While PEL estimates provided in this study should be considered preliminary, our framework for testing combined behavior-driven movement models and population dynamics models is an improvement compared to earlier efforts.
Highlights
Worldwide, over 58,000 dams and diversion structures (>15 m height) have been constructed to provide water supply, flood control, and hydroelectric power generation (ICOLD 2015)
The analysis presented in this paper largely compares predictions from the behaviordriven movement model (BMM) and population dynamics models to observed spatial and temporal changes in catch from fish field surveys, as well as to daily salvage data from state and federal fish screening facilities
The proportional entrainment loss (PEL) estimate from the BMM and population model that fit the data from WY 2002 best was 35%, which is more than double the estimates of adult Delta Smelt PEL from Kimmerer 2008 and 2011 of 15% and 13%, respectively
Summary
Over 58,000 dams and diversion structures (>15 m height) have been constructed to provide water supply, flood control, and hydroelectric power generation (ICOLD 2015). The presence and operations of these facilities can adversely affect native fish populations through habitat fragmentation, reductions in habitat quantity and quality, enhancement of non-native species, and direct losses from entrainment mortality (Rytwinski et al 2017). Entrainment loss is one of the most obvious effects because it is often observed through tagging, fish sampling in diverted water, or collection of dead fish on screens and louvers. The net effect of entrainment on the viability of fish populations has been challenging to determine, in part because the proportion of the population that is lost to entrainment is often not known. This uncertainty hampers evaluation of entrainment reduction measures
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
