Hardhead Silverside, Atherinomorus stipes

Hardhead Silverside, Atherinomorus stipes. Fish caught in coastal waters off Islamorada, Florida, December 2013. Length: 5.1 cm (2.0 inches). Catch, photograph and identification courtesy of Ben Cantrell, Peoria, Illinois.

Hardhead Silverside, Atherinomorus stipes. Fish caught in coastal waters off Islamorada, Florida, July 2021. Length: 6.1 cm (2.4 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.

Hardhead Silverside, Atherinomorus stipes. Fish caught in coastal waters off Islamorada, Florida, December 2013. Length: 6.5 cm (2.6 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

The Hardhead Silverside, Atherinomorus stipes, is a member of the Old World Silverside or Atherinidae Family, and is known in Mexico as tinícalo cabezón. Globally, there are eleven species in the genus Atherinomorus with only one found in Mexican waters, the species described herein which is found in the Atlantic Ocean.

The Hardhead Silverside has an elongated relatively deep bodies with a rounded cross section. They are translucent and silvery pale olive in color and have a silver stripe that is narrow at the front, broadens toward the rear, and overlies a black stripe on the sides. Their caudal fin has 2 series of black dots along the sides; in mature fish, and also also a black tip. Their head is wide and relatively deep with a straight profile. They have disproportionately large eyes and a fairly large terminal mouth that opens at the front and is equipped with small teeth set in narrow bands on the jaws. Their anal fin has 1 spine and 11 to 13 rays; their caudal fin is forked; their first dorsal fin has 4 to 6 spines and originates before the anal fin; their second dorsal fin has 1 spine and 8 to 10 rays is located after the anal fin; and, their pectoral fins have 14 or 15 rays. Their body is covered with small scales.

The Hardhead Silverside is a schooling pelagic species found in shallow waters over reefs and adjacent soft bottoms at depths up to 10 m (35 feet). They reach a maximum length of 10.0 cm (3.9 inches). They are active daytime feeders that consume zooplankton. Reproduction is oviparous with large masses of sticky eggs released by females several times per year; the eggs attach themselves to shallow water seaweed via long filaments and are then fertilized by males. The larvae are planktonic. The Hardhead Silverside is poorly studied with very limited information available about their lifestyle and behavioral patterns, including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Hardhead Silversides are found in all waters surrounding the Yucatán Peninsula including both the Gulf of Mexico and the Caribbean.

The Hardhead Silverside is similar to and can be confused with the Reef Silverside, Hypoatherina harringtonensis (silver stripe wide at front).

From a conservation perspective the Hardhead Silverside is currently considered to be of Least Concern with stable, widely distributed populations. Due to their small stature they are of limited interest to most. They are used on a limited basis as bait fish. They are also an important food source for a wide variety of fish, marine mammals, and sea birds.