Acipenser gueldenstaedtii Brandt and Ratzeburg, 1833 – Native (Fig. 16) Acipenser pygmaeus Reisinger [J.] 1830: 93, Objectively invalid; preoccupied by Acipenser pygmaeus Pallas 1814. Acipenser gueldenstaedtii Brandt [J. F.] & Ratzeburg [J. T. C.] 1833: 13; Type locality: Caspian Sea and tributaries; Black Sea. No types known. Acipenser aculeatus Lovetsky [A.] (ex Fischer) 1834: 262; Type locality: Dnjepr River in Jekaterinoslaw/Yekaterinoslav Province, Russia. Acipenser gueldenstadti var. colchica Marti [V. J.] 1940: 869; Type locality: Southeastern part of Black Sea near mouth of Rioni and Inguri rivers, Georgia, Eurasia. Syntypes: (many). Acipenser gueldenstadti var. tanaica Marti [V. J.] 1940: 863; Type locality: Taganrog Bay, Sea of Azov, Russia. Syntypes: (many). Common name: Pr: Chalbash, Tasmahi-ye Rus, Mahi-ye kaviar En: Russian Sturgeon. Diagnosis: Often mis-identified with A. persicus but can be distinguished by the short, blunt snout and triangular shape. In addition, belly color in A. gueldenstaedtii is yellowish-white and back is golden-brown. Other diagnostic characters are: longer interorbital distance from A. persicus, smaller stellate bony plates between the dorsal and ventral rows and snout length less than 60% HL. Meristic characters: D: 26–51, A: 18–35, GR: 15–36, DS: 5–19, LSC: 21–50, VS: 6–14. Distribution: Caspian Sea basin (Fig. 17). The species has been recorded from every river between Astara River in the west to Gorgan River in the east. In recent year (Coad 2015), it has been reported from Atrak, Gorgan, Gharasu, Tajan, Babol, Haraz, and Sefidrud rivers (southern Caspian Sea). Nowadays the access to many rivers is restricted by reduced water flow, construction, weirs, dams, irrigation canals and pollution. This species is probably currently only found in the estuary of some large rivers as Sefidrud and Tajan rivers. Taxonomy. Conservation: IUCN: Critically Endangered A2bcde (Gessner et al. 2010a).

Published as part of Jouladeh-Roudbar, Arash, Ghanavi, Hamid Reza & Doadrio, Ignacio, 2020, Ichthyofauna From Iranian Freshwater: Annotated Checklist, Diagnosis, Taxonomy, Distribution and Conservation Assessment, pp. 1-14 in Zoological Studies 59 (21) on pages 14-15, DOI: 10.6620/ZS.2020.59-21, http://zenodo.org/record/12822787