Alosine Restoration in the 21st Century: Challenging the Status Quo

Abstract

Despite the expenditure of millions of dollars on restoration efforts for depleted North American stocks of alosine fishes, rangewide abundance levels for multiple species have declined to historic lows. Stocking practices aimed at rebuilding spawning runs are deemed successful when numerical abundance levels are shown to increase in response. However, these practices may only yield short‐term gains in abundance at the ultimate expense of population genetic integrity and do not ensure the long‐term persistence and evolutionary potential of a species. Although molecular methods are now widely employed in fisheries management and provide a suite of powerful management tools, these approaches have not been well integrated into alosine management strategies. We review the net effects of stocking practices on population genetic integrity and species’ long‐term persistence as it is currently understood and highlight what is known in this regard for alosines in North America, with particular focus on American shad Alosa sapidissima. We find that stocking practices carry a substantial risk to the persistence of genetically distinct alosine spawning populations and suggest that future restoration efforts proceed by providing access to historical spawning grounds, either through dam removal or through providing effective fish passage, followed by natural recolonization of reclaimed habitat. We also identify important areas of research relevant to future alosine restoration that require exploration and identify recent developments that may alter future restoration decisions in an adaptive management framework. Received March 18, 2011; accepted October 6, 2011

Human disturbance causes the formation of a hybrid swarm between two naturally sympatric fish species

“…The benefits of dam removal for the restoration of anadromous fishes have been largely discussed in the context of replenishing historic spawning runs (e.g. Hasselman & Limburg ). Our study provides evidence that dam removal could also help maintain species integrity for alewife and blueback herring.…”

Evaluating the potential for prezygotic isolation and hybridization between landlocked and anadromous alewife (Alosa pseudoharengus) following secondary contact

“…Species in the genus Alosa (shad and river herring) have been identified as the second most prevalent genus in threatened freshwater ecoregions, with 14 of 25 alosine species located in heavily obstructed river systems (Bernhardt et al., ; Vörösmarty et al., ). In North America, alewife ( Alosa pseudoharengus ) is the target of conservation management plans along the Atlantic coast using fishway installations to restore migratory pathways to historical spawning grounds (Hasselman & Limburg, ; Lake, Ravana, & Saunders, ). Many of the systems targeted for restoration contain independently evolving populations of landlocked alewife, the freshwater resident form of anadromous alewife, in lakes and reservoirs above the dams (Palkovacs et al., ).…”

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

“…The 343 hydropower plants account for 945 turbines with an installed capacity of 11,058 MW [45]. Though currently not federally listed, in many areas along the East Coast, American shad numbers are well below historical numbers and some runs are considered to be at an all-time low [10][11][12]. If populations continue to decline, there is potential that American shad could be added to the federal list of endangered and threatened wildlife, at which point they would fall under the protection of the Endangered Species Act.…”

“…Today, Pacific coast populations of American shad are very abundant, such as in the Columbia River where the average run in the last decade exceeded 3 million individuals and was the highest on record in 2019, with nearly 7.5 million returning adults [9]. However, most Atlantic coast populations are declining [10][11][12]. As a result, many states on the Atlantic coast have restrictions or moratoriums on American shad fishing, which prompted the development of an interstate fisheries management plan [13][14][15].…”