4) Gobioides peruanus (Steindachner, 1880);

Gobiidae .

Peruvian Eel-Goby, Smalleye Eel-Goby; Gobio-Anguila de Barro (Fig. 2F).

Diagnosis: This species differs from the other species of the family occurring in the freshwaters of the country (Pacific) by the following combination of characters: body very elongate (depth 9.0–14.0% of SL), compressed and eel-like; head small (5.0–8.0% of SL); dorsal fin long, with seven flexible spines and 14–15 rays; anal fin rays 15; caudal fin long, pointed and broadly joined to dorsal and anal fins; and coloration pattern (see Robertson & Allen 2015).

Basis of the record: A single specimen was observed and recorded in photo in the Quebrada Bomba Vieja (Barranca River basin), near the mouth of the río Barranca, El Roble, Puntarenas (9.96228, -84.73493), at 6 m. a.s.l., on January 6, 2021, by Beto Guido Méndez (Bird watcher guide/Naturalist).

Remarks: This species inhabits brackish tidal rivers and estuaries as well as freshwaters; lives in muddy burrows (Robertson & Allen 2015).