Seminar Home

1 December

Dan Hasselman

Research Associate, UW Aquatic & Fishery Sciences

From Founding Fish to Invasive Species: Contrasting Views of American Shad in Their Native and Introduced Range

Abstract

American shad are an anadromous clupeid of increasing conservation concern on both the Atlantic and Pacific coasts of North America, but for very different reasons. The species historically supported an important commercial fishery in their native (Atlantic) range, but a combination of anthropogenic factors has resulted in dramatic rangewide declines in abundance and extirpations of spawning runs. Despite fishery closures and ongoing restoration efforts, native rangewide abundance of American shad has continued to decline to historic all time lows, and exhibits no signs of recovery. On the contrary, American shad in their introduced (Pacific) range have become prolific. American shad were introduced to the Sacramento River, CA, in 1871 to support a growing human population in San Francisco, but the species rapidly dispersed and colonized additional rivers along the Pacific coast. American shad have since been reported from the waters off Baja Mexico to the Anadyr River, Russia. The species also now constitutes the single largest spawning run of any anadromous fish in the Columbia River, and outnumbered all native salmonids combined from 1977-2008. Although the spread of aquatic invasive species is a global concern, the specific impacts of invasive American shad in Pacific coastal ecosystems are equivocal. Despite their presence in the region for well over a century the species persists in relative obscurity, having not been the subject of much scientific investigation, and remains ecologically overlooked and evolutionarily underappreciated. The goals of this synthesis are to overview the current state of biological knowledge of American shad in both their native and introduced ranges, provide historical context for future examinations of shad along the Pacific coast, and to highlight areas of research that require immediate investigation.

Bio

I have broad interests in evolutionary biology, molecular ecology, and conservation. My research explores the evolution of wild anadromous fish populations over contemporary time scales, and aims to bridge the gap between academia and application by employing molecular and non-molecular tools to provide linkages between evolutionary biology and practical conservation.

My research has examined the full ontogenetic development of the endangered Atlantic whitefish – a Canadian endemic restricted to Nova Scotia, and the development of morphological criteria for accurate discrimination of this species from morphologically similar coregonine fishes at all life history stages.

More recently my attention has focused on American shad, a species of increasing conservation concern on both the Atlantic and Pacific coasts of North America, but for very different reasons (see abstract). My dissertation examined the distribution of neutral genetic variation and spatial scale of population structure from across the species’ native range (Atlantic coast). My post-doctoral research examines American shad in their introduced range (Pacific coast), and their ecological and evolutionary role as an invasive species in Pacific coastal ecosystems.

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