Longfin Dace, Agosia chrysogaster
Longfin Dace, Agosia chrysogaster, Breeding Male. Fish caught from a small creek in the greater Phoenix, Arizona. Length: 6.8 cm (2.7 inches). Catch, photograph, and identification courtesy of Ben Cantrell, San Diego, California.
Longfin Dace, Agosia chrysogaster, Male. Fish caught from a small creek in the greater Phoenix, Arizona. Length: 7.2 cm (2.8 inches). Catch, photograph, and identification courtesy of Ben Cantrell, San Diego, California.
Longfin Dace, Agosia chrysogaster, Male. Fish caught from a small creek in Peoria, Arizona, August 2020. Length: 10 cm (3.9 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
The Longfin Dace, Agosia chrysogaster, is a member of the Carp and Minnow or Cyprinidae Family, and is known in Mexico as pupo panzaverde. Globally, this is the only species in the genus Agosia of which is found in the freshwater systems of Mexico.
The Longfin Dace is a silvery minnow with a dark back and white on the belly. Some fish have a dark band along the sides just above the midsection with an enlarged black spot at the caudal fin base and iridescent gold flecks may develop on the upper sides of both sexes. Breeding males have some yellow on the lower parts of their paired fins for a brief time. Their head has a rounded snout, a slightly subterminal mouth and they have a small barbel at the corner of their mouth. Their anal fin has 7 rays, and in large females the lower lobe is elongated; their dorsal fin originates slightly before the pelvic fins.
The Longfin Dace is a highly adaptable, very hardy fish that occurs in diverse situations ranging from low-elevation desert streams to cool, clear mountain streams, at elevations up to 2,000 m (6,600 feet). They are found in sandy and rocky runs and flowing pools of creeks and small to medium rivers, and in eddys and pools, often near cover. They reach a maximum of 10 cm (3.9 inches) in length. They are omnivorous, feeding on various aquatic invertebrates and plants depending on availability. They have the ability to survive high temperatures and low dissolved oxygen conditions as-well-as low water environments by taking refuge in algae mats and moist detritus. These fish are highly opportunistic, moving rapidly through flowing water during periods of high runoff and travelling amazing distances in a relatively short amount of time. They reproduce in a few days following stream rejuvenation by summer rains with spawning occurring in shallow depressions in fine sand along the shoreline at depths of 5 cm (2 inches) to 20 cm (8 inches). The eggs are buried; the young remain in the nest until the yolk sac is mostly absorbed before moving to stream edges.
In Mexico the Longfin Dace is native to the freshwater Pacific Ocean drainages of Western Mexico including the Concepción River in Sonora.
From a conservation perspective the Longfin Dace is currently considered to be of Least Concern with stable, widely distributed populations. They are prone to habitat destruction and the disappearance of natural water supplies and interactions with newly introduced non-native fishes. They are utilized as a baitfish and have been introduced to new areas via bait bucket releases.