Assessment of Extinction Risk and Reasons for Decline in Sturgeon

Abstract

Sturgeon populations in the Danube River have been affected by a combination of hydropower development, over-harvesting, habitat degradation from agricultural and industrial practices and from urbanization. The effects of these changes have been monitored on six sturgeon species inhabiting the Danube River. Two of them are resident species, while the other four migrate to the river for spawning. Atlantic sturgeon (Acipenser sturio) has completely disappeared from this region. Ship sturgeon (Acipenser nudiventris) is very rare in professional fishing catches. Beluga (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), stellate sturgeon (Acipenser stellatus) and sterlet (Acipenser ruthenus) are endangered with different levels of extinction risk. Here, we model the time dependence of the beluga and Russian sturgeon catch in the Serbian part of the Danube River. Predicted extinction of Russian sturgeon was estimated to fall around the middle of the century, and for beluga approximately at middle of the millennium. Suggestions for sturgeon conservation measures on a national level and coordination of all relevant institutions in Serbia are also presented.

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

“…Dams were constructed on large rivers for mechanical or hydroelectric power, for navigation purposes or to facilitate transport of material downstream, directly blocking access to and/or altering sturgeon spawning habitat. Dramatic chan ges to water quality due to use of rivers for disposal of industrial or municipal effluent, deforestation and urbanization of watersheds were all prevalent practices in the period post over-harvesting concurrent with dam construction (Rochard et al 1990, Birstein et al 1997, Lenhardt et al 2006. Consequently, riverine fish (i.e.…”

“…More recently, water quality conditions in many regions have improved (Hensel & Holcik 1997, Schram et al 1999, Kampa et al 2014) and stricter harvest controls have been implemented (Khodorevskaya et al 1997, Baker & Borgeson 1999, Peterson et al 2007) in addition to the enforcement of import restrictions on many sturgeon species through the Convention on International Trade in Endangered Species (Williamson 2003, Lenhardt et al 2006, Ludwig 2006. However, poaching purportedly remains a conservation concern for all sturgeon species, given the exorbitant prices of caviar (Cohen 1997, Pikitch et al 2005; this seems to be especially relevant for European stocks (Khodorevskaya et al 1997, Ivanov et al 1999, Ludwig 2006).…”

“…Sturgeon recovery efforts have historically been extensive and expensive (Bacalbasa-Dobrovici & Patriche 1999, Lenhardt et al 2006, Guti 2014 in areas where populations have drastically declined, such as the Danube River (Hensel & Holcik 1997) or Yangtze River (Wei et al 1997, Dudgeon 2010. The relatively unperturbed populations in northern Canada provide an opportunity to learn about sturgeon biology, and to identify habitat needs and reproductive potential in a natural riverine environment.…”

Evaluating the genetic consequences of river fragmentation in lake sturgeon (Acipenser fulvescens Rafinesque, 1817) populations

“…This contrasts with the widely held and empirically supported hypothesis that population declines from over-exploitation and fragmentation lead to declines in genetic diversity through genetic drift and increased risk of inbreeding (Willi et al, 2006;DiBattista, 2008; but see Landguth et al, 2010). Lake Sturgeon in the Ottawa River and other large river systems have undergone drastic declines due to commercial harvest and habitat degradation during the past 150 years (Lenhardt et al, 2006;Peterson et al, 2007;Haxton and Findlay, 2008). Habitat degradation and fragmentation by dams continues to decrease their abundance and impede restoration efforts (Schueller and Hayes, 2011) by altering spawning behavior and reducing recruitment (Auer, 1996b;Haxton and Findlay, 2008).…”

Insight into Danube sturgeon life history: trace element assessment in pectoral fin rays

“…It used to be inhabited by six sturgeon species: Atlantic sturgeon (Acipenser sturio), ship sturgeon (Acipenser nudiventris), beluga (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), stellate sturgeon (Acipenser stellatus) and sterlet (Acipenser ruthenus). Unfortunately, the Atlantic and ship sturgeon are, respectively, considered to be extinct and possibly extinct within the Danube basin, while the latter four species are facing different levels of extinction risk (Reinartz 2002;Williot et al 2002;Lenhardt et al 2006;Jarić et al 2009). …”