Abstract
Author(s): Lessard, JoAnna; Cavallo, Brad; Anders, Paul; Sommer, Ted; Schreier, Brian; Gille, Daphne; Schreier, Andrea; Finger, Amanda; Hung, Tien-Chieh; Hobbs, James; May, Bernie; Schultz, Andrew; Burgess, Oliver; Clarke, Robert | Abstract: An extreme decline in Delta Smelt (Hypomesus transpacificus) abundance has led to a number of management actions to support this endangered species, including the development and refinement of culture techniques and the creation of a refuge population. The wild Delta Smelt population has diminished to the point that many in the scientific community believe population supplementation using cultured fish needs to be experimentally evaluated as a possible management tool. Concerns about supplementation include the effectiveness of this action, and its potential to divert attention and funding from other needed management actions such as habitat restoration. Here, we describe the outcomes of a 2-day workshop that described the current refuge population, and identified key issues for potential future use of cultured Delta Smelt for research and management. Expanded use of cultured Delta Smelt is controversial and requires consideration for complexities that include legal constraints and permitting requirements. Developing policies that allow for in situ experiments using cultured Delta Smelt appears to be a precursor for advancing policies that might allow supplementation actions. Releases of cultured fish, either experimentally or as a management action, clearly need to be conducted within an adaptive management program that is integrated with other strategies, including habitat restoration. We describe a general framework for evaluating the potential risks of supplementation and include suggestions for how to reduce risks and uncertainty. Overall, we conclude there is sufficient baseline information about Delta Smelt and the existing culture program to proceed with targeted field research that utilizes cultured fish. Finally, given the dire status of this species, we conclude that rapid progress toward the development of a viable and testable supplementation program must be a priority for Delta Smelt conservation.
Highlights
Delta Smelt (Hypomesus transpacificus) is a small estuarine fish endemic to the upper reaches of the San Francisco Estuary (Moyle 2002; Bennett 2005; IEP– MAST 2015)
Population abundance decreased further around 2002, which included declines of several other pelagic fishes of the upper estuary—a phenomenon known as the “Pelagic Organism Decline” (POD) (Sommer et al 2007; Thomson et al 2010; IEP–MAST 2015)
In agreement with a previous workshop (Hobbs et al 2017), the 2017 workshop concluded that the status of Delta Smelt is serious enough that hatchery supplementation needs to be considered as part of future management strategies developed within a decision-analysis framework
Summary
Delta Smelt (Hypomesus transpacificus) is a small (maximum length ~120 mm FL) estuarine fish endemic to the upper reaches of the San Francisco Estuary (estuary) (Moyle 2002; Bennett 2005; IEP– MAST 2015). This requirement is a key barrier to this permitting route for Delta Smelt experimental releases and reinforcement actions, because there is only one, continuous population; Section 10(j) may be useful for hydrologically-isolated, wetland-based research studies Based on these considerations, and comments from regulatory staff at the workshop and in later discussions, permitting is expected to potentially be a challenging issue. An important consideration in the timing of these actions is that— it would be preferable to first restore the habitat conditions necessary to improve the status of wild populations— hatchery production and supplementation using cultured Delta Smelt may be the only viable, shortterm means to prevent extinction This is often the case when natural production of imperiled or ESAlisted species is likely both habitat- and stock-limited, such as with endangered Kootenai River White Sturgeon (Anders 1998; Anders et al 2002; Ireland et al 2002). Adaptive management is a special case of SDM for decisions that are iterative or linked over time
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
