Dwarf Perch, Micrometrus minimus
Dwarf Perch, Micrometrus minimus. Fish caught from coastal waters off San Diego, California, August 2018. Length: 9.3 cm (3.7 inches). Catch, photograph and identification courtesy of Ben Cantrell, San Diego, California.
Dwarf Perch, Micrometrus minimus. Fish caught off the Oceanside Pier, Oceanside, California, April 2006. Length: 10.0 cm (3.9 inches).
Dwarf Perch, Micrometrus minimus. Fish caught from coastal waters off San Diego, California, August 2018. Length: 12.8 cm (5.9 inches). Catch, photograph and identification courtesy of Ben Cantrell, San Diego, California.
Dwarf Perch, Micrometrus minimus. Fish caught from coastal waters off Tijuana, Baja California, February, 2023. Length: 12.8 cm (5.9 inches). Catch, identification and photograph courtesy of Luke Ovgard, Klamath Falls, Oregon.
The Dwarf Perch, Micrometrus minimus, is a member of the Surfperch or Embiotocidae Family, that is also known as the Dwarf Surfperch and in Mexico as mojarra enana. There are two global members in the genus Micrometrus, and both are found in Mexican waters of the Pacific Ocean.
The Dwarf Perch have highly compressed deep oval bodies with a depth that is 43% to 47% of standard length. They are silvery with black edged scales, random blotches on their sides, and a series of faint stripes on their sides behind their pectoral fins. They have a large black blotch at the base of their pectoral fins and a dark line just below their dorsal fin commencing at the fourth dorsal spine. Their head has a concave upper profile with large eyes and an oblique mouth. Their anal fin has 3 spines; their caudal fin is forked; and, their dorsal fin has 7 to 9 spines and 19 to 28 soft rays. Their body is covered with disproportionately large scales. Their lateral line is prominent.
The Dwarf Perch are typical bottom dwelling inhabitants of inshore exposed rocky reefs including rocky tidal pools, eelgrass (Zostera) in bays, and around jetties at depths up to 30 feet. Females reach a maximum of 16.0 cm (6.3 inches) length and males are only about half this length. The Dwarf 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. Females reach sexual maturity in one year and significantly outnumber males, except at birth, indicating that males die off soon after birth. They express strong sexual dimorphism with males being smaller than females and slower growing. Males live about half as long as females (one year versus two or three years). Males are also unique among all spiny rayed fish in that they have more anal fin rays than females. They prefer water temperatures between 11oC (52oF) and 21oC (70oF); if water temperatures exceed 23oC (74oF) they will escape to cooler deeper waters. Juveniles feed on small crustaceans, amphipods, polychaetes, and mollusks. As they mature, their diet changes to partially herbivore and then to omnivore. Reproduction is viviparous with mating occurring in the summer. Gestation lasts six months with each female producing 2 to 50 fry annually that are 2.5 cm (1.0 inch) to 3.5 cm (1.4 inches) in length; larger females produce larger quantities of fry.
The Dwarf Perch is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found only from Cedros Island, Baja California, northward along the central and northwest coasts of Baja.
The Dwarf Perch is straightforward to identify due to its body profile and coloration and is therefore not easily confused with any other species.
From a conservation perspective the Dwarf Perch has not been formally evaluated. They are exceedingly small in stature and have no commercial or economic value. They are normally a “catch and release”, however, are retained by subsistence fishermen. They are a favorite of beginning anglers and are a minor component of the pier fishery. They are also used as live bait on a limited as-available basis.