Longnose Killifish, Fundulus similis

Longnose Killifish, Fundulus similis. Fish caught from coastal waters off Anclote Key, Florida, May 2015. Length: 6.3 cm (2.5 inches). Catch, photograph and identification courtesy of Ryan Crutchfield, Tampa Florida.

Longnose Killifish, Fundulus similis. Fish caught from coastal waters off Corpus Christi, Texas, July 2020.  Length: 8.8 cm (3.5 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Longnose Killifish, Fundulus similis. Fish caught on Cedar Key, Florida, March 2018. Length: 8.9 cm (3.5 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Longnose Killifish, Fundulus similis. Fish caught from coastal waters off Anclote Key, Florida, May 2015. Length: 9.1 cm (3.6 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

The Longnose Killifish, Fundulus similis, is a member of the Topminnow and Killifish or Fundulidae Family, that is known in Mexico as sardinilla narigona. Globally, there are thirty-nine species in the genus Fundulus, of which five are found in Mexican waters, four in the Atlantic and one in the Pacific Ocean.

The Longnose Killifish has a slender elongated round body with a straight profile. They are olive to silvery in color with 9 to 13 narrow dark bars on the body and caudal fin. They are sexually dimorphic with the males have a dark blotch on the top cover of the gill cover, yellow tinges on the lower head and caudal fin and a black spot just below the rear of the dorsal fin. They have flattened heads with and elongates sharp snout and a small oblique protrusible mouth that opens in the front and ends under the center of the eyes that is equipped with an outer row of pointed conical teeth and an inner band of simple teeth. Their anal fin has 9 to 13 rays; their caudal fin is bluntly rounded; their dorsal fin has a 11 to 13 rays and has a short base and is located before the anal fin, their pectoral fins have 16 to 21 rays, are inserted low on the sides with a narrow base a narrow base; and, their pelvic fins are small and found well behind the pectoral fins. They have 6 to 10 short gill rakers. They are covered with smooth scales.

The Longnose Killifish is a common tropical benthopelagic non-migratory species that are found in shallow waters near structures, in coastal marshes, mangroves and tidal flats, and short distances upstream in coastal rivers, at depths up to 1 m (3 feet). They reach a maximum of 15 cm (5.9 inches) in length. They feed on planktonic and benthic invertebrates. They are a key component of the food web in coastal marshes being preyed upon by fish, birds, and mammals. The Longnose Kllifish 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 Longnose Killifish is a resident of Mexican waters of the Atlantic Ocean but has a limited distribution being found in coastal waters along the West coast of the Gulf of Mexico from the Texas border southward to Tampico, Tamaulipas.

The Longnose Killifish is a straight forward identification but might be confused with the Yucatán Killifish, Fundulus persimilis (short snout; very thin bars).

From a conservation perspective the Longnose Killifish is currently considered to be of Least Concern with stable, widely distributed populations. Their long term viability is threatened by human coastal development. They are utilized by the aquarium trade at a nominal level as they are difficult to maintain. They are also utilized as a bait fish.