Esmaeilius isfahanensis (Hrbek, Keivany & Coad, 2006)

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 738-739

Esmaeilius isfahanensis

Common name. Esfahan killifish.

Diagnosis. Distinguished from other species of Esmaeilius by: ● male with black dorsal, pelvic and anal margins / ●

Esmaeilius isfahanensis ; Zayandeh, Iran; female, 35 mm SL.

Esmaeilius isfahanensis ; Zayandeh, Iran; male, 32 mm SL.

female mottled with many large blotches or narrow bars on flank, usually fused into a midlateral, wide, dark-brown band / ○ 25–29 total scales along lateral series / ○ female with a distinctive black spot at caudal base. Size up to 45 mm SL.

Distribution. Iran: Lower Zayandeh drainage (e.g., Hasan Abad, Malvajerd qanats).

Habitat. Springs and spring-fed streams.

Biology. Live up to 3 years, mature in a few months at about 25 mm SL, usually late in year of birth. Males establish territories along banks, usually in dense vegetation but also between rocks, which they defend against rival males. Spawns April–July. Females spawn with one or more males, usually in algae or other vegetation near surface or in gravel beds. Few eggs are laid in the substrate during a spawning event. Individual females may produce several clutches in one day. Feeds on algae, detritus, and small invertebrates.

Conservation status. CR; appears to be declining within its very small range. May have disappeared from Varzaneh. Remarks. Esmaeilius sophiae inhabits Gavkhoni marshes in very lower Zayandeh drainage. The black spot at the caudal base in the female is much more pronounced in small individuals and fades in large adults of more than 25 mm SL.

Further reading. Hrbek et al. 2006 (description); Keivany 2013 (biology); Esmaeili et al. 2020b (molecular data and distribution); Freyhof & Yoğurtçuoğlu 2020 (genericposition).

Isolation of endorheic Kor basin. In West Asia, numerous rivers do not reach the sea but terminate in lakes or marshes that are often hypersaline. These rivers are known as endorheic rivers and endorheic basins, in contrast to exorheic rivers that flow to the sea. One of the many endorheic rivers in Iran is the Kor, which has been the subject of considerable study. During the Quaternary period, the Palaeo-Kor drained to the Persian Gulf via the Mond River. From the late Quaternary (20,000 years ago) until the Holocene (2000 years ago), the exorheic drainage was closed due to the tectonic uplift of the Zagros Mountains. This resulted in the Kor becoming endorheic and isolated from the exorheic Mond. Unsurprisingly, most species currently found in the endorheic Kor are the same as those found in the Mond and other adjacent tributaries of the Persian Gulf. The isolation of the Kor occurred relatively recently. However, this may be a partial story. While two endemic fish species, Esmaeilius shirini and Oxynoemacheilus tongiorgii , are present in the Kor, several species found in the Mond are absent in the Kor, including Capoeta mandica , and Garra rufa . Conversely, Chondrostoma regium occurs in the Kor but is absent in the Mond. Clearly, the biogeography of the Kor is far more complex and its connection to the Lake Maharlo basin (home to the endemic E. persicus ) also requires further investigation. Further reading. Gholami et al. 2014 (geology).

Esmaeilius persicus ; Pirbanoo spring, Iran; female, ~ 30 mm SL. Esmaeilius persicus ; Pirbanoo spring, Iran; male, ~ 30 mm SL.