Panamic Sergeant Major, Abudefduf troschelii
The Panamic Sergeant Major, Abudefduf troschelii, whose common Spanish name is petaca banderita, is a species in the Damselfish or Pomacentridae Family, known collectively as castañetas and jaquetas in Mexico. Globally, there are twenty-five species in the genus Abudefduf, four of which are found in Mexican waters, two in the Atlantic and two in the Pacific.
The Panamic Sergeant Majors have relatively deep oblong compressed bodies with a depth that is 54 to 58% of standard length, thus similar in nature to freshwater bluegills. They are whitish to pale silvery green in color with a bright yellow back and dark bars across the side of their body and caudal peduncle. Their head has a steep profile and a small protrusible mouth with a single row of teeth. Their caudal fin is forked with broad lobes. They have two anal spines and 10 to 13 rays and a single continuous dorsal fin with 13 spines and 12 or 13 rays. They have 23 to 33 gill rakers. Their lateral line is incomplete and ends under the edge of their dorsal fin base. Their body is covered with rough scales.
The Panamic Sergeant Majors are a non-migratory species found in shallow water over and within rocky reef structures buffeted by wave action at depths up to 50 feet. They reach a maximum length of 23.0 cm (9.1 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. While breeding, males turn a very dark metallic blue to attract females to their nesting site, then guard and aerate the eggs.
In Mexican waters the Panamic Sergeant Majors are found in all waters of the Pacific with the exception that they are absent from Magdalena Bay northward along the central and northwest coasts of Baja.
The Panamic Sergeant Major, due to its barring pattern and yellow coloration is not easily confused with any other species, however, it is virtually identical to the Sergeant Major, Abudefduf saxatilis (found only in the Atlantic Ocean) and is similar in color to the Graybar Grunt, Haemulon sexfasciatum (rectangular oblong body; six or seven bars).
The Panamic Sergeant Majors are rather small but are considered an excellent food fish. They are classic nibblers, thus difficult to hook.
Panamic Sergeant Major, Abudefduf troschelii, juvenile. Fish collected with a bait net off the surface in coastal waters off Loreto, Baja California Sur, June 2017. Length: 3.8 cm (1.5 inches). Catch and photo courtesy of Chris Wheaton, Fullerton, CA. Discussions with H.J. Walker, Jr. Scripps Institution of Oceanography, La Jolla, CA are indicative that this is most definitely from the Genus Abudefduf but he was unable to confirm the species without a thorough examination of the specimen.
Panamic Sergeant Major, Abudefduf troschelii. Fish caught from shore at La Bocana, Baja California Sur, April 2016. Length 18.5 cm (7.3 inches). Note the atypical bronze coloration.
Panamic Sergeant Major, Abudefduf troschelii. Underwater photo taken in the greater Cabo San Lucas area, Baja California Sur, November 2017. Length: ca. 20 cm (7.9 inches).