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D. Ross Robertson (1) Mariana Mena Alcántar (1) Gilberto Ponce Tejeda (1)

Description: Body wider than its height at pectoral girdle area, progressively compressed from pectoral to caudal peduncle, ventrally flattened from pectoral girdle to anal origin. Lateral line sloping ventrally on anterior one-third, extending posteriorly to caudal peduncle, bending abruptly onto dorsal lobe of caudal. Dorsal spine relatively short and thick, shorter than pectoral spine; anterior margin granulated on basal two-thirds, with weak serrations on distal third; posterior margin smooth on basal third, distal third with weak serrations. Seven dorsal soft rays. Pectoral spine moderately long and thick; two-thirds of anterior margin weakly granulated, with weak serrations on distal third; posterior margin straight on basal one-fourth, distal three-fourths with weak serrations. Nine to eleven pectoral soft rays. Posterior process of cleithrum triangular smooth to rugose, slightly visible. Pelvic fin deep and large at base, with six rays, and well-developed fleshy protuberances in adult females. Adipose fin low, with base moderately long, shorter than anal base. Anal fin moderately high and long at base, with 16–19 rays and ventral profile convex. Caudal peduncle moderately high. Caudal-fin forked, dorsal and ventral lobes relatively long, dorsal lobe somewhat longer than ventral lobe, slightly pointed. Colouration in alcohol: Head and body dark brown to bluish above, whitish below; dorsal surfaces of pelvic proximally black, distally lighter; anal dark, distal tips lighter; caudal grayish to blackish. Sexual Dimorphism: Only females have well-developed fleshy protuberances or pads in basal portion of pelvics, especially during reproductive season. Vomerine tooth patches and accessory tooth patches not observed directly, but possibly showing same variation described for A. canteri and A. jimenezi. Etymology: The specific name guatemalensis: from Guatemala. Remarks: Günther (1864) described Arius guatemalensis based on specimens collected on the Pacific side of Guatemala. In recent literature ( Kailola & Bussing, 1995 ; Ferraris, 2007 ), two nominal species have been considered junior synonyms of Ariopsis guatemalensis, Arius caerulescens , described by Günther (1864) based on two specimens from Guamuchal (=Huamuchal) in Guatemala , and Galeichthys azureus , described by Jordan & Williams (1895) based on a unique specimen from an estuary at Mazatlán ( Sinaloa ), western Mexico. There is little conflict in the literature about the taxonomic status of Galeichthys azureus, as junior synonym of A. guatemalensis. Arius caerulescens ( sensuJordan & Gilbert, 1882 ; Jordan & Evermann, 1896 ; Eigenmann & Eigenmann, 1890 ; Regan, 1906,1908) is accepted as a synonym of A. guatemalensis based on characters recognised in present study as sexually dimorphic (e.g., the vomerine tooth plates continuous with larger clubshaped palatine, vs. oblong or oval, continuous or not, with palatine patches a little larger than vomerine in A. guatemalensis ) or show ontogenetic variation (e.g., maxillary barbel extending to the opercle or near to base of pectoral; vs. extending beyond the base of pectoral in A. guatemalensis).

Blue sea catfish

Arius guatemalensis, Arius cærulescens, Galeichthys azureus,

Ariidae

North America: Pacific coast and coastal rivers of North and Central America, from Gulf of California, Mexico to Honduras. Type locality: Estuary at Mazatlán, Sinaloa, W. Mexico.

45.0cm. TL (18ins)

26-29°c (79-85°f)

7.0-8.5.

D R Robertson and Gerald R Allen. 2015. Shorefishes of the Tropical Eastern Pacific: online information system. Version 2.0 Smithsonian Tropical Research Institute, Balboa, Panamá.
Ferraris, C.J. Jr., 2007. Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types. Zootaxa 1418:1-628.
Fishes of the East Pacific.
Froese, R. and D. Pauly. Editors. 2019. FishBase. World Wide Web electronic publication. www.fishbase.org, ( 12/2019 ).
Kailola, P.J. and W.A. Bussing, 1995. Ariidae. Bagres marinos. p. 860-886. In W. Fischer, F. Krupp, W. Schneider, C. Sommer, K.E. Carpenter and V. Niem (eds.) Guia FAO para Identification de Especies para lo Fines de la Pesca. Pacifico Centro-Oriental. 3 Vols. FAO, Rome.
Marceniuk, Alexandre P., Acero, Arturo, Cooke, Richard, Betancur-R, Ricardo (2017): Taxonomic revision of the New World genus Ariopsis Gill (Siluriformes: Ariidae), with description of two new species. Zootaxa 4290.