Longfin Silverside

Longfin Silverside, Atherinella eriarcha

The Longfin Silverside, Atherinella eriarcha, whose common Spanish name is plateadito plateado, is a species in the New World Silverside or Atherinopsidae Family, known collectively as charales and pejerreyes in Mexico. Globally, there are thirty-six species in the genus Atherinella, seven of which are found in Mexican waters, two in the Atlantic and five in the Pacific.

The Longfin Silversides have elongated and relatively deep bodies with a rounded cross section. They are translucent and pale silvery-olive in color with narrow scale outlines and a broad silver stripe on their sides that narrows into a large diamond on their caudal fin base. Their head is large with disproportionately large eyes and a fairly large terminal mouth that opens in the front. Their anal fin has one spine and 27 rays; their caudal fin is forked; their first dorsal fin originates over the anal fin and has four plus one spines and 11 or 12 rays; and their pectoral fins are short and reach the middle of the pelvic fins. They are covered with smooth scales.

The Longfin Silversides are a schooling pelagic species found in shallow intertidal waters, coastal bays, and near coastal reefs at depths up to 35 feet. They reach a maximum length of 8.0 cm (3.2 inches). They are active daytime feeders that consume algae and small crustaceans. Reproduction is oviparous with large masses of sticky eggs released by females several times per year. These eggs attach themselves to shallow water seaweed via long filaments and are then fertilized by males. The larvae are planktonic.

In Mexican waters the Longfin Silversides are found from Guerrero Negro southward along the central and southwest coasts of Baja, in the lower half of the Sea of Cortez, and along the coast of the mainland south to Guatemala.

The Longfin Silverside is similar to, and can be confused with, the Broadstripe Silverside, Atherinella nesiotes (stripe wider than eye) and the Pitcher Silverside, Atherinella nepenthe (last dorsal fin ray over last anal fin ray).

The Longfin Silversides are of limited interest to most due to their small size, however, they are an important food source for a wide variety of fish, marine mammals, and sea birds. From a conservation perspective they are believed to be common and widespread, thus classified as of Least Concern, however, their population status and trends are unknown.

Longfin Silverside (1)

Longfin Silverside, Atherinella eriarcha. Fish collected by hand off the beach, Cabo Real, Baja California Sur, December 2014. Length: 2.5 cm (1.0 inch). Can also be found on occasion in the bait tanks of commercial bait salesmen.

Longfin Silverside, Atherinella eriarcha. Fish collected by hand off the beach, Cabo Real, Baja California Sur, December 2017. Length 2.6 cm (1.0 inch).

Longfin Silverside, Atherinella eriarcha. Fish caught from coastal water off Mazatlán, Sinaloa, October 2017. Length: 6.0 cm (2.4 inches). Catch and photo courtesy of George Brinkman, Guelph, Ontario, Canada. An impressive catch via hook and line on size 27 micro-hooks.