Concurrent Sessions C: Prioritization - Strategic Fish Passage Barrier Prioritization in the Tillamook - Nestucca Subbasin, Oregon

Agriculture Leaders Theater, Oregon State University

Anthropogenic barriers to fish movement have and continue to negatively impact fish populations. In the Pacific Northwest, these barriers are typically dams, culverts, or tide gates. Frequently, fish passage barrier removal occurs in an ad-hoc, opportunistic fashion across the landscape without regard for a strategic focus of which projects might yield the greatest benefit at the population level. In response to this, new initiatives have been developed with a more strategic focus, using optimization models to arrive at the best barrier removal solutions for limited or constrained resources. A group of federal and state agencies in Oregon have developed a Focused Fish Passage Demonstration Project (FFPDP) centered on the coastal Tillamook-Nestucca sub-basin, in hopes of highlighting the benefits of a strategic sub-basin-focused approach. As part of this effort, the best-available barrier and habitat data was obtained for the sub-basin, and an optimization model used to generate the optimum solutions for given assumptions or budget scenarios. A ranked list of top priority barriers to remove was generated under differing habitat quality assumptions, and several potential FFPDP budgets were utilized as cost constraints to develop optimal fish passage barrier removal scenarios. Compiling available data revealed that 270 manmade barriers obstruct passage to over 250 miles of fish-bearing streams in the study area. Optimization model analysis showed that strategically prioritizing future investments on a relatively small subset of barriers could produce substantial gains in connectivity. In the absence of more detailed data, this analysis remains a rough prioritization, but the aim has been to treat the prioritization for the sub-basin as a living document which can be updated with better information as it becomes available.