Reef Perch, Micrometrus aurora

Reef Perch, Micrometrus aurora. Fish caught from coastal waters off Santa Cruz, California, August 2018. Length: 12.8 cm (5.9 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

The Reef Perch, Micrometrus aurora, is a member of the Surfperch or Embiotocidae Family, that is also known as the Reef Seaperch and in Mexico as mojarra de arrecife. There are two global members in the genus Micrometrus, and both are found in Mexican waters of the Pacific Ocean.

The Reef Perch have highly compressed deep oval bodies with a depth that is 36% to 42% of standard length. They are a silvery blue color with green and black on their backs, yellow or orange-yellow stripes on their lower sides and black tipped scales posterior of the pectoral fins. They also have a black patch at the base of their pectoral fins. Their head has a concave upper profile with large eyes and an oblique mouth. Their anal fin has 3 spines and 17 to 21 rays; their caudal fin is forked; their first dorsal fin has 7 to 9 spines, their second dorsal fin has 15 to 19 soft rays, and, their pectoral fins have 17 to 20 rays. They have 18 to 21 gill rakers. Their body is covered with disproportionately large scales. Their lateral line is prominent.

The Reef Perch are found in the intertidal zone within shallow rocky areas, shallow reefs, and tidal pools that have an abundance of algae and surfgrass at depths up to 6 m (20 feet). Females reach a maximum of 18 cm (7.1 inches) length and males are only about half this length. The Reef Perch are of significant scientific interest because they are only one or two global fish having males born sexually mature, i.e. ready to rumble. They express strong sexual dimorphism with females being larger than the males, are faster growing and have long life spans. Males live about half as long as females (four years versus six). They feed on algae, gammarid amphipods, isopods and copepods. Reproduction is viviparous with each female producing 5 to 30 fry annually that are released in lower tidal pool areas that are 2.5 cm (1.0 inch) in length.

The Reef Perch is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found only from Punta Baja, Baja California, northward along the northwest coast of Baja.

The Reef Perch is straightforward to identify due to the series of half rings on the scales between the anal and pectoral fins and the black patch at the base of the pectoral fins.

From a conservation perspective the Surf Perch has not been formally evaluated. They are small in stature, have no commercial or economic value and of limited interest to most. They are a very rare catch by a recreational angler.