Jacksmelt, Atherinopsis californiensis

Jacksmelt, Atherinopsis californiensis. Fish caught from coastal waters within Bahía Santa Rosalillita, Baja California, August 2019. Length: 22.9 cm (9.0 inches). Catch and photograph courtesy of Barry Mastro, Escondido, California.

Jacksmelt, Atherinopsis californiensis. Fish caught off the Oceanside Pier, Oceanside, California, May 2006. Length: 23.0 cm (9.1 inches).

Jacksmelt, Atherinopsis californiensis. Fish caught from coastal waters off Santa Cruz, California, May 2016. Length: 25.0 cm (9.8 inches). Catch, photograph, and identification courtesy of Andrew Hansen, Santa Cruz, California.

The Jacksmelt, Atherinopsis californiensis, is a member of the New World Silverside or Atherinopsidae Family, that is known in Mexico as pejerrey mocho. Although this fish is a smelt by name, it is not considered a true smelt. Globally, there are two species in the genus Atherinopsis, only this one being found in Mexican waters, the species described herein found in the Pacific Ocean.

The Jacksmelt has an elongated and somewhat compressed body. They are silvery overall being greenish-blue dorsally and silvery ventrally. They have a bright yellow patch on their cheeks and a silvery-gray stripe with a blue border on their sides. Their head is oblong and compressed with a pointed snout, small eyes, and a small terminal mouth that is extendible and equipped with 2 or 3 rows of conical teeth. Their anal fin has 1 spine and 21 to 26 rays and is inserted midway between the origins of their first and second dorsal fins; the first dorsal fin has 5 to 9 spines; the second dorsal fin has 1 spine and 10 rays; their pectoral fins are short just reaching the pelvic fin origin; and, their pelvic fins are closer to the anal fin origin than to the pectoral fin origin. They have 30 to 40 rounded gill rakers. Their body is covered with small smooth scales.

The Jacksmelt is a schooling pelagic species found in bays and shallow murky waters over sandy bottoms and around piers from the surf zone to depths up to 30 m (100 feet). They are the largest member of the Silverside Family and reach a maximum length of 49 cm (19 inches). They are active daytime feeders and consume algae and small crustaceans. Reproduction is oviparous with large masses of sticky eggs released by females several times per year; eggs attach themselves to shallow water seaweed via long filaments and are then fertilized by males. The larvae are planktonic. They have a lifespan of up to 11 years.

The Jacksmelt is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found only along both coasts of Baja; they are absent from Guaymas, Sonora, to Guatemala along the west coast of the mainland.

The Jacksmelt is similar to, and can be confused with, the California Grunion, Leuresthes tenuis (first dorsal fin origin over anal fin origin) and the Topsmelt, Atherinops affinis (first dorsal fin origin behind anal fin origin).

From a conservation perspective the Jacksmelt is currently considered to be of Least Concern, with stable, widely distributed populations. They are a favorite of California pier fishermen where they are normally caught on high tides with baited or unbaited Sabiki rigs. If one is hooked often several others will be hooked on the reel. They are also caught by surf fishermen. On light tackle, they are a reasonable foe for their size. They are consumed as a food fish and sold commercially in Asian markets. They have numerous small bones, however. Historically they were an important food source for Native Americans. They are an important food source for a wide variety of fish, marine mammals, and sea birds.