Optimal Fish Passage Barrier Removal—Revisited

Abstract

Infrastructure, such as dams, weirs and culverts, disrupt the longitudinal connectivity of rivers, causing adverse impacts on fish and other aquatic species. Improving fish passage at artificial barriers, accordingly, can be an especially effective and economical river restoration option. In this article, we propose a novel, mixed integer programing model for optimizing barrier mitigation decisions given a limited budget. Rather than simply treating barriers as being impassable or not, we consider the more general case in which barriers may be partially passable. Although this assumption normally introduces nonlinearity into the problem, we manage to formulate a linear model via the use of probability chains, a newly proposed technique from the operations research literature. Our model is noteworthy in that it can be readily implemented and solved using off-the-shelf optimization modelling software. Using a case study from the US State of Maine, we demonstrate that the model is highly efficient in comparison with existing solution methods and, moreover, highly scalable in that large problems with many thounsands of barriers can still be solved optimally. Our analysis confirms that barrier mitigation can provide substantial ecological gains for migratory fish at low levels of investment.

Aquatic biodiversity in forests: a weak link in ecosystem services resilience

“…The cost of local stream-crossing restoration projects typically ranges from approximately $50,000 to over $500,000 USD per crossing (Reagan 2015), and across the landscape can total to billions of dollars (US GAO 2001;Neeson et al 2015). Accordingly, one of the major challenges for managers is economic: estimating the short-and long-term costs of restoration and scaling priorities appropriately to efficiently target limited available funding to address multiple objectives (King and O'Hanley 2014;Neeson et al 2015;Reagan 2015). Recent work on the biological effectiveness of passage restoration has strongly emphasized the importance of scaling.…”

“…The primary challenges include: (1) identifying biological trade-offs (e.g., benefits to native species, threats from invasion of non-native species; Fausch et al 2006); (2) short-and long-term costs of restoration (King and O'Hanley 2014;Reagan 2015); (3) prioritizing restoration at local versus regional extents (Neeson et al 2015); and (4) considering biodiversity in the context of other societal benefits associated with transportation infrastructure (Reagan 2015). The cost of local stream-crossing restoration projects typically ranges from approximately $50,000 to over $500,000 USD per crossing (Reagan 2015), and across the landscape can total to billions of dollars (US GAO 2001;Neeson et al 2015).…”

Prioritising culvert removals to restore habitat for at‐risk salmonids in the boreal forest

“…But numerous impediments to restoration exist, such as the lack of barrier inventory data available for different jurisdictions (Januchowski-Hartley et al 2013); thus there is a pressing need to undertake systematic inventories of stream crossings to determine the spatial extent of barriers at both state/ provincial and national scales (Januchowski-Hartley et al 2013). For example, King and O'Hanley (2014) used a similar optimisation model to assess barrier mitigation across the entire state of Maine. For example, King and O'Hanley (2014) used a similar optimisation model to assess barrier mitigation across the entire state of Maine.…”

“…Qualitative estimates were converted into quantitative values; full barriers and partial barriers were assigned values of 0 and 0.5, respectively;Diebel et al 2015;King & O'Hanley 2014). The passage evaluation scores barriers as either fully passable to all species and life stages, partially passable (barrier at high flows or to some species and some life stages at most flows) and completely impassable by all fish species and life stages.…”

Cohort‐specific variation in juvenile coho salmon habitat use

“…King & O'Hanley, 2016;O'Hanley, 2011) could be extended to account for ontogenetic movement among habitats during freshwater residency (forthcoming report). For example, existing fish passage barrier removal optimisation models (e.g.…”