A global perspective of fragmentation on a declining taxon—the sturgeon (Acipenseriformes)

Abstract

Acipenseriformes (sturgeons and paddlefishes) are considered to be one of the most globally imperiled taxon, with 25 of the 27 species listed by the International Union for the Conservation of Nature (IUCN). Overharvest, habitat degradation, fragmentation and water quality issues have contributed to their decline worldwide. These stressors have been ameliorated in some areas, but in others they remain a limiting factor to sturgeon. Barriers impeding upstream migrations to natural spawning areas and manifesting alterations to natural flows continue to compromise sturgeon recruitment and limit natural recovery. Watersheds in the Northern Hemisphere have been categorized as being strongly affected, moderately affected or unaffected based on the degree of fragmentation and water flow regulation. An overlay (i.e. intersect) of the sturgeons' status with this watershed categorization revealed that a small area remains in which sturgeon are not considered at risk and where rivers are unaffected in northern Canada. These relatively unperturbed populations provide a much needed opportunity to learn about sturgeon biology, habitat needs and reproductive potential in a natural riverine environment, which may facilitate conservation and recovery efforts in affected watersheds.

Freshwater eels: A symbol of the effects of global change

“…Of course, temperate eels are not the only species endangered by global change and most diadromous fishes have undergone severe declines (Limburg & Waldman, ; McDowall, ; Mota et al., ). The effects of fragmentation (Haxton & Cano, ; Larinier, ; Limburg & Waldman, ), global warming (Elliott & Elliott, ; Friedland, ; Friedland, Hansen, Dunkley, & MacLean, ; Jonsson & Jonsson, ; Lassalle, Béguer, Beaulaton, & Rochard, ; Lassalle et al., ; Rougier et al., ), fisheries and pollution (Limburg & Waldman, ; McDowall, ) have been documented for most of these species. More generally, most migratory animals regardless of taxa have undergone similar declines (Berger, Young, & Berger, ; Sanderson, Donald, Pain, Burfield, & van Bommel, ; Wilcove & Wikelski, ) raising the question of sustainability of migratory tactics in the face of global change.…”

“…Another component is the modification of habitats due to anthropogenic land use, which can lead to fragmentation of aquatic and terrestrial ecosystems or even habitat loss (Brook, Sodhi, & Bradshaw, ; Collinge, ; Fischer & Lindenmayer, ). Habitat loss and ecosystem fragmentation are currently considered major threats to biodiversity and represent one of the major challenges in ecosystem conservation and restoration (Sutherland et al., ; Tilman, May, Lehman, & Nowak, ; Tischendorf & Fahrig, , ), by impairing the ability of individuals to migrate to essential habitats (Gros & Prouzet, ), by isolating populations and reducing gene flow (Haxton & Cano, ; Horreo et al., ), and by modifying species community structure (Perkin & Gido, ). Fragmentation and habitat loss increase the risk of extinction cascades (Fischer & Lindenmayer, ; Haddad et al., ; Junge, Museth, Hindar, Kraabøl, & Vøllestad, ; Krauss et al., ; van Leeuwen, Museth, Sandlund, Qvenild, & Vøllestad, ; Terborgh et al., ).…”

Short‐Term Physiological Disruption and Reflex Impairment in Shortnose Sturgeon Exposed to Catch‐and‐Release Angling

“…The Acipenseriformes are a primitive order of megafuanal bony fishes comprising the paddlefishes (Polyodontidae) and sturgeons (Acipenseridae). This group of species is considered the most frequently imperilled with extinction (Haxton and Cano ), and 25 of the 27 sturgeon species are listed by the International Union for the Conservation of Nature (IUCN). Imperilment of sturgeons has predominantly been associated with habitat fragmentation, which restricts the ability of sturgeons to migrate to spawning grounds (Birstein et al.…”

Sturgeon and paddlefish life history and management: Experts' knowledge and beliefs

“…A population model of the European sturgeon indicated that fishing mortalities as low as 5% can reduce previously undisturbed populations to no more than 20%–30% of their historic spawning biomass, mainly at the expense of older age‐classes (Jarić & Gessner, ). Reliable longevity estimates require access to undisturbed sturgeon populations, which are rare (Haxton & Cano, ; Jarić & Gačić, ). Longevity is also dependent upon the latitude, with more northern ranges being characterized by a delayed maturity and longer lifespans.…”