Freshwater Fishes of North America: Volume 1: Petromyzontidae to Catostomidae

Chapter 5 Acipenseridae: Sturgeons

the bottom of rivers, lakes, and oceans, locating and eating invertebrates and fishes from the bottom with the aid of taste buds on the barbels and ampullary organs on the underside of the head, which use electroreception to detect the weak electrical fields emitted by prey. Although some Sturgeons spend most of their lives in the oceans or estuaries, they all spawn in freshwater rivers where they were hatched, some migrating ≤1,200km (746 miles) to spawn. Newly hatched larvae passively drift in river currents ≤530km (329 miles). Sturgeons are highly vulnerable to human activities, especially overfishing and dams that block migratory routes; therefore, almost all Sturgeons worldwide are considered imperiled. Their roe (eggs), which are processed into caviar, have been valued by humans for >1,000 years. DIVERSITY AND DISTRIBUTION In North America, Sturgeons occur along both coasts and in inland fresh waters (Figs. 5.1 and 5.2). Two species of Acipenser (Fig. 5.1), the Green Sturgeon (Acipenser The Acipenseridae consist of 25 extant species in 4 genera , including 17 species in Acipenser, 2 in Huso, 3 in Pseudoscaphirhynchus , and 3 in Scaphirhynchus (Birstein & Bemis 1997; Birstein et al. 1997a; Billard & Lecointre 2001; Ludwig 2008). The word “acipenser” is the Latin name for Sturgeon. Sturgeons occur on all continents in the Northern Hemisphere and are almost completely restricted to the northern temperate zone (Bemis & Kynard 1997; Choudhury & Dick 1998). The greatest diversity of Sturgeons is in western Europe (11 species) and central Asia, including the Mediterranean, Aegean, Black, Caspian, and Aral Seas, which is referred to as the Ponto-Caspian region (Bemis & Kynard 1997). Five species of Acipenser and three species of Scaphirhynchus occur in North America . Sturgeons are the largest freshwater fishes and are long-lived (e.g., >150 years old). Originally described as Sharks in the 1700s due to the cartilaginous skeleton, jaw structure, and shark-like tail, Sturgeons are actually ancient bony fishes with fossils that date to 175mya. They have a toothless, protrusable mouth on the underside of the head with four barbels just before the mouth and five rows of bony plates along the body. Sturgeons cruise along Chapter 5 Acipenseridae: Sturgeons Bernard R. Kuhajda Plate 5.1. White Sturgeon, Acipenser transmontanus ACIPENSERIDAE: STURGEONS 161 and Atlantic Sturgeon (Acipenser oxyrinchus) (Fig. 5.1). Shortnose Sturgeons inhabit coastal waters along the eastern seaboard from New Brunswick, Canada, to northern Florida. Two subspecies of the Atlantic Sturgeon are recognized . The nominate form, A. oxyrinchus oxyrinchus, is distributed along the Atlantic Coast from northern Quebec and Newfoundland, Canada, to northern Florida. The Gulf Sturgeon (A. oxyrinchus desotoi) is restricted to coastal areas in the Gulf of Mexico from Tampa Bay, Florida , to Louisiana, and perhaps westward to the Rio Grande, Texas and Mexico (Lee et al. 1980; Page & Burr 1991; Wilson & McKinley 2004; Nelson et al. 2004). The Lake Sturgeon (Acipenser fulvescens) (Fig. 5.1) and all species of Scaphirhynchus (Fig. 5.2) occur in fresh water in middle North America. The Lake Sturgeon is found in lakes and rivers from Hudson Bay, Great Lakes, and St. Lawrence River drainages from Alberta to Quebec, Canada, south to the lower Mississippi and Coosa River drainages, Louisiana and Alabama. The Alabama Sturgeon (Scaphirhynchus suttkusi) is restricted to the Mobile Basin in large rivers in Alabama and formerly in Mississippi . The Pallid Sturgeon (Scaphirhynchus albus) is nearly restricted to the Missouri and Mississippi Rivers proper from Montana to Louisiana but does use the lower reaches of major tributaries. The Shovelnose Sturgeon (Scaphirhynchus platorynchus) is distributed throughout the Mississippi River basin, including the Missouri and Ohio River drainages, from Montana to Pennsylvania, south to Louisiana, and had a historical population in the Rio Grande, New Mexico (Lee et al. 1980; Page & Burr 1991; Wilson & McKinley 2004; Nelson et al. 2004). Polyploidization and Diversity Polyploidization is one of the main genetic mechanisms of speciation within Acipenseriformes (Sturgeons) and has contributed to the diversification within Acipenser. The diploid ancestor of all Acipenseriformes had a karyotype of 60 chromosomes that produced a tetraploid (4n) ancestor with 120 chromosomes through a gene duplication event (Birstein et al. 1997b; Ludwig et al. 2001; see genetics medirostris) and the White Sturgeon (Acipenser transmontanus ), are restricted to the North Pacific region. Green Sturgeons occur along 3,000km (1,864 miles) of coastal and estuarine areas from the Aleutian Islands, Alaska, to central California, and into Mexico (Lee et al. 1980; Page & Burr 1991; Moyle 2002; Wilson & McKinley 2004; Nelson et al. 2004). The White Sturgeon was once considered...