Shiner Perch, Cymatogaster aggregata
The Shiner Perch, Cymatogaster aggregata, whose common Spanish name is mojarra brillosa, is a member of the Surfperch or Embiotocidae Family, known collectively as mojarras viviparas in Mexico. There is only one member in the genus Cymatogaster, the fish described herein, which is found in Mexican waters of the Pacific.
The Shiner Perch have highly compressed elongated “football-shaped” fusiform oval bodies with a typical “perch-like” shape and a depth that is 33 to 37% of standard length. They are silvery and have a dusky greenish back with fine horizontal bars and three broad yellow vertical bars on their sides. They have fine black dots on their sides toward their head. Their anal, pectoral, and pelvic fins are transparent; their caudal and dorsal fins are transparent to dusky. Breeding males are black and covered with dark speckles. Their anal fin has 3 spines and 22 to 25 rays; their caudal fin is forked; and their dorsal fin is continuous with 8 to 11 spines and 19 to 22 rays. Their lateral line is slightly arched and complete. Their body is covered with large scales.
The Shiner Perch are found in heavily vegetated and structured shallow water bays and estuaries within eelgrass beds. They are often found in large schools around piers and jetties and in adjacent brackish and fresh water systems. The Shiner Perch are found demersal in tidal pools and in the surf zone at depths up to 480 feet. They reach a maximum length of 21.0 cm (8.3 inches) with both males and females being of equal length. They reside in waters that range from 7oC (45oF) to 24oC (75oF) and are absent from waters above 25oC (77oF). They are diurnal feeders with juveniles consuming zooplankton, such as copepods, then transitioning to algae, crustaceans, and mollusks as they mature. Reproduction is viviparous and occurs in November and December with males exhibiting an elaborate courtship toward females. Gestation lasts five to six months with each female producing 3 to 36 fry measuring 3.0 cm (1.2 inches) to 4.0 cm (1.6 inches); larger females produce larger litters. Females carry the developing young until they mature. They are generally non-migratory but will make seasonal inshore-offshore movements; they will move to deeper waters during the winter and pregnant females will move to shallow waters in the spring to give birth. They have a lifespan of up to nine years. The Shiner Perch are of scientific interest as they are one of the 15 to 20% of all living fish that are labriform swimmers. They use their pectoral fins rather than their caudal fin for swimming and flap their fins much like swimming penguins.
In Mexican waters the Shiner Perch have a limited distribution being found only from Bahia San Quintin northward along the northwest coast of Baja
The Shiner Perch is straightforward to identify due to its elongated body profile and coloration and is therefore not easily confused with any other species.
The Shiner Perch are caught during the summer months in abundance in various locations along the west coast of the United States on small hooks and light tackle utilizing shrimp, small pieces of fish, small crabs, squid, and dough. They are especially popular among beginning anglers as they are abundant and easy to catch. They are, however, a minor component of the pier fishery. They are sold commercially on a limited basis. Although exceedingly small, they are considered an excellent food fish. They can also be found in public aquariums and are used on occasion as bait fish for larger prey.
Shiner Perch, Cymatogaster aggregata. Fish caught off the Municipal Wharf #2, Monterey, CA, August 2012. Length: 15.0 cm (6.0 inches). Catch, photo and identification courtesy of Kenneth Tse, Toronto, Ontario, Canada.