Goldfish

Characteristics

Goldfish have many unusual body forms with a variety of colors. Bulge-eyed and multiple tailed forms are commonly produced for aquariums, but normal body form is robust and laterally compressed. The natural color is olive-brown dorsally to bronze-gold laterally and yellowish-white ventrally. Black, gold, bronze, orange, red, pink, and white, or combinations of these colors are often found. Serrated spinous rays occur at the front of the dorsal and anal fins, which distinguishes goldfish from the native minnows. The complete lateral line has 25 to 30 scales. The dorsal fin, which is much longer than those of native minnows, has 15 to 19 soft rays, while the pectoral fins have 15 to 17 soft rays, and the pelvic fins usually have 9 soft rays.

Distribution

Exotic to Iowa; mostly introduced from bait buckets or aquarium. Wild populations have been found throughout the forested portions of northeast Iowa including several in the Cedar, Shellrock, Winnebago and Mississippi Rivers and their tributaries. It has also been collected in sporadic locations throughout Iowa with fish found in the Iowa, Des Moines, Skunk and Missouri Rivers. Reproducing Goldfish populations are also found in many man-made lakes and impoundments across Iowa.

Foods

Zooplankton and aquatic larval insects.

State Record

State Records are not documented for non-game species.

Expert Tip

Iowa law prohibits releasing Goldfish into public water, but you can use Goldfish as bait (placed on a hook while fishing).

Details

Self-sustaining populations of Goldfish can be found in natural standing water along streams and below hatcheries where large populations are maintained from fish that have escaped. They can also be found in large impoundments where they are often used as bait. Goldfish, very tolerate of turbidity and high organic content, can sometimes be found in the most polluted streams. In Iowa, Goldfish select fairly specific habitats, sluggish water or pools with lots of aquatic plants, limiting their distribution. Cultured Goldfish are easy prey because of their showy colors and domesticated nature. 

Superficially, Goldfish look like Common Carp, but several features separate them. Goldfish lack barbels on the upper jaw, and the thin-lipped mouth is terminal. Body scales on Goldfish do not have the dark spot, and no cross-hatching pattern is present. Internally, the pharyngeal teeth of Goldfish are arranged along a single row in 4-4 sequence, and they have heavy arches with the crowns at an angle.

Hybridization with Common Carp is known where both species live in the same waters. Spawning takes place from April through August as the female scatters adhesive eggs in shallow, vegetated water at random. Large female Goldfish produce over 200,000 eggs.

In Iowa, adult fish typically are 8- to 16-inches long and weigh up to 2-pounds. This species is used extensively as bioassay animals for scientific purposes and has widespread use because it is hardy and easily kept in confinement. Iowa law prohibits release of Goldfish into public water, but Goldfish can be used as bait (placed on a hook while fishing).

Recent stream sampling information is available from Iowa DNR's biological monitoring and assessment program.

Sources:

Harlan, J.R., E.B. Speaker, and J. Mayhew. 1987. Iowa fish and fishing. Iowa Conservation Commission, Des Moines, Iowa. 323pp.

Loan-Wilsey, A. K., C. L. Pierce, K. L. Kane, P. D. Brown and R. L. McNeely. 2005. The Iowa Aquatic Gap Analysis Project Final Report. Iowa Cooperative Fish and Wildlife Research Unit, Iowa State University, Ames.

Photo Credit: photo courtesy of Windsor Aguirre, Gulf Coast Research Laboratory Museum Institute of Marine Sciences and Gulf States Marine Fisheries Commission.