Dusky Damselfish

Dusky Damselfish, Stegastes adustus

The Dusky Damselfish, Stegastes adustus, whose common Spanish name is jaqueta prieta, is a species in the Damselfish or Pomacentridae Family, known collectively as castañetas and jaquetas in Mexico. Globally, there are forty species in the genus Stegastes, eleven of which are found in Mexican waters, seven in the Atlantic and four in the Pacific.

The Dusky Damselfish have oval robust compressed bodies with a depth that is 44 to 52% of standard length becoming deeper with maturity, thus similar in nature to freshwater bluegills. Adults are uniformly gray-brown in color including their body and fins. Juveniles are similarly colored but with a red-brown cap on the nape of their neck and upper edge of their body, blue spotted lines on their head and upper front of their body, a large black-blue ringed ocellus on the lower part of their dorsal fin and upper body adjacent to their dorsal spines, and a small black spot bordered by blue on their upper caudal fin base. Their head has a small protrusible mouth that opens in the front with a single row of teeth. Their anal fin has two spines and 13 to 15 rays; their caudal fin is bluntly forked with bluntly rounded lobes; and their dorsal fin is singular and continuous with 12 spines and 14 to 17 rays. Their anal and dorsal fins are short and blunt and do not reach past the caudal fin base. They have 9 or 10 gill rakers on their lower arch. Their lateral line is incomplete and ends under the edge of their dorsal fin base. Their body is covered with large rough scales.

The Dusky Damselfish are found in shallow reefs within the surge zone at depths up to 65 feet but normally at depths of less than 20 feet. They reach a maximum length of 10.5 cm (4.1 inches). They are diurnal feeders consuming primarily algae, plankton, and benthic invertebrates. Reproduction is oviparous with pairing of individuals; eggs are distributed demersal and adhere to the substrate due to their stickiness. They are poorly studied and very little is known about their behavioral patterns.

In Mexican waters the Dusky Damselfish are found in all waters of the Atlantic.

The Dusky Damselfish can be confused with a series of other Damselfish including the Beaugregory, Stegastes leucostictus (blue dorsally and yellow ventrally), the Bicolor Damselfish, Stegastes partitus (white on the rear half of body), the Cocoa Damselfish, Stegastes variabilis (yellow caudal and pectoral fins), the Freshwater Gregory, Stegastes otophorous (yellow anal, caudal, dorsal, and pectoral fin tips), the Longfin Damselfish, Stegastes diencaeus (blue line at anal fin margin; blue pectoral fins), the Purple Reeffish, Chromis scotti (blue and gray color), and the Yellowtail Damselfish, Microspathodon chrysurus (blue spotting on upper body).

The Dusky Damselfish are exceedingly small and of limited interest to most. They are classic nibblers, thus difficult to catch by hook and line.

Dusky Damselfish, Stegastes adustus. Fish caught from coastal waters off Sugarloaf, Key, Florida, August 2014. Length: 9.1 cm (3.6 inches). Catch, photo and identification courtesy of Dean Kimberly, Atlanta, GA.

Dusky Damselfish, Stegastes adustus. Fish caught from coastal waters off Sugarloaf, Key, Florida, August 2014. Length: 12.2 cm (4.8 inches). Catch, photo and identification courtesy of Dean Kimberly, Atlanta, GA.