A dam passage performance standard model for American shad

Abstract

Objectives for recovery of alosines commonly involve improving fish passage at dams during migration. However, a quantitative basis for dam passage performance standards is largely absent. We describe development of a stochastic life-history-based simulation model for American shad, Alosa sapidissima, to estimate effects of dam passage and migratory delay on abundance, spatial distribution of spawning adults, and demographic structuring in space and time. We used the Penobscot River, Maine, USA, as a case study to examine sensitivity of modeled population metrics and probability of achieving specific management goals to inputs. Spawner abundance and percentage of repeat spawners were most sensitive to survival and migration delay at dams, marine survival, and temperature cues for migratory events. Recovery objectives related to abundance and spatial distribution of spawners were achievable under multiple scenarios, but high rates of upstream and downstream passage were necessary. The simulation indicated trade-offs between upstream and downstream passage efficacy whereby increased downstream passage was required to maintain or increase population abundance in conjunction with increased upstream passage. This model provides a quantitative support tool for managers to inform ecologically based decisions about a suite of management scenarios to facilitate recovery and sustainability of diadromous fish populations.

Evaluation of Fish Passage at a Nature‐Like Rock Ramp Fishway on a Large Coastal River

“…Simulation modeling suggested that migratory delays (especially downstream) are more detrimental than reduced passage for American Shad populations along the northeast Atlantic coast, as mortality reduces repeat spawners in iteroparous populations (Castro‐Santos and Letcher ; Stich et al. ). Nature‐like fishways may be an improvement for downstream passage over other fishway designs, as delays were minimal and passage efficiency was high for American Shad and Striped Bass at LD‐1.…”

“…Flathead Catfish predation on American Shad has also been observed by Ashley and Buff (1987) in the Cape Fear River and by Raabe and Hightower (2014a) in the Little River. Delays for American Shad can be especially detrimental in terms of energy loss, as they consume minimal food in rivers and are more likely to succumb to predation or harvest (Castro-Santos and Letcher 2010; Raabe and Hightower 2014a;Stich et al 2018). Detection records showed tagged American Shad (including ones at LD-1) being suddenly undetected in the array, indicating that they potentially succumbed to starvation, predation, or harvest.…”

“…Immediately downstream of LD-1, many acoustic-tagged American Shad experienced delays (e.g., only 33% passed within a week), and we observed numerous individuals in eddies to the side of the main fishway flow during electrofishing, something also observed by Haro and Castro-Santos (2012). Simulation modeling suggested that migratory delays (especially downstream) are more detrimental than reduced passage for American Shad populations along the northeast Atlantic coast, as mortality reduces repeat spawners in iteroparous populations (Castro-Santos and Letcher 2010; Stich et al 2018). Nature-like fishways may be an improvement for downstream passage over other fishway designs, as delays were minimal and passage efficiency was high for American Shad and Striped Bass at LD-1.…”

The Susceptibility of Juvenile American Shad to Rapid Decompression and Fluid Shear Exposure Associated with Simulated Hydroturbine Passage

“…In late summer and fall, the recently hatched juveniles migrate downstream to the ocean, at which point they typically range in size from 7 to 15 cm [6]. Most of these fish are iteroparous, so healthy population dynamics rely heavily on the successful downstream migration of both juveniles and adults [6,8].…”

Surgical Implantation of Acoustic Tags in American Shad to Resolve Riverine and Marine Restoration Challenges

“…Riverine spawning migrations of American Shad are relatively well characterized; fish passage preferences and information from directed fisheries and historical landings have also been examined (Moser et al 2000;Limburg et al 2003;Bailey et al 2004;Haro and Castro-Santos 2012;Grote et al 2014;Raabe and Hightower 2014;Waldman et al 2014). However, less is known about the interannual survival, movements, and behavior of postspawn American Shad outside of rivers (Leggett 1977;Melvin et al 1986;Dadswell et al 1987) despite a need for such information (ASMFC 2010; Hightower and Harris 2017; Stich et al 2019). Efforts to improve fish passage (where possible), closures of directed fisheries, and management of bycatch in nondirected fisheries have had limited success, with most individual river stocks still being at or near historic lows (ASMFC 2007).…”