Anadromous Sturgeons: Habitats, Threats, and Management Synthesis and Summary
Jean Munro, Randy E. Edwards, and Andrew W. Kahnle
Anadromous sturgeons spend most of their lives at sea and migrate into rivers to spawn (Bemis and Kynard 1997). This migratory pattern includes not only species from coastal oceanic waters, but also species from the mesohaline Ponto-Caspian seas (Rochard et al. 1991). Oceanic anadromous species include European sturgeon Acipenser sturio, Atlantic sturgeon A. oxyrinchus oxyrinchus, Gulf sturgeon A. o. desotoi, green sturgeon A. medirostris, Sakhalin sturgeon A. mikadoi, and Chinese sturgeon A. sinensis. Species migrating back and forth from freshwaters to estuaries, but dependent on estuarine feeding for their growth, are called amphidromous, an example of which is the shortnose sturgeon A. brevirostrum (Kynard 1997). Semianadromous sturgeons like the white sturgeon A. transmontanus comprise populations that grow in estuaries and migrate upriver to spawn, but generally include also potamodromous populations, which migrate in rivers or lakes (Doroshov 1985). Both amphidromous and semianadromous sturgeons can travel long distances in oceanic waters. This symposium focused on oceanic anadromous sturgeons, hereafter termed anadromous sturgeons, but also included papers regarding shortnose sturgeon and white sturgeon. Sakhalin sturgeon and Chinese sturgeon were not discussed during the symposium.
The sturgeon family Acipenseridae is one of the most threatened fish families (Birstein et al. 1997; IUCN 2006), and there are highly (European sturgeon) and moderately (Atlantic sturgeon) threatened species among the anadromous sturgeons. In recent decades, two major types of management measures that increase the hope for recovery of anadromous sturgeons have been implemented. First, fishing has been banned for nearly all populations. Second, renewed consideration of the importance of habitat in restoration efforts has resulted in increased habitat research and new habitat protection measures. In protection or restoration plans, designations such as essential or critical habitat (Endangered Species Act 1973; Magnuson- Stevens Fishery Conservation and Management Act 1996; Species at Risk Act 2003; IUCN red list (IUCN 2006)) can be powerful management tools if supported by adequate scientific definitions and content. Many papers summarized below in the habitat section contribute to our understanding of the ecological function of essential habitats. Threats to habitats and to populations are covered in a second section. Finally, a review of the papers on management and population trends examines whether progress has been made by the U.S. Atlantic sturgeon populations since fishing was banned. In this synthesis, we summarize the contents of the symposium papers, making occasional reference to presentations not reported as papers. We emphasize the main findings, using common agreements reached by the researchers in the symposium discussion panels. We also provide selected references for background information. This compendium of papers, bearing on sturgeon species with similar life histories, will contribute to development of sound conclusions and recommendations regarding the ecology and management of anadromous sturgeons.