Blackfin Splitfin

Blackfin Splitfin, Goodea atripinnis

The Blackfin Splitfin, Goodea atripinnis, whose common Spanish name is tiro, is a member of the Splitfin or Goodeidae Family, known collectively as mexclapiques in Mexico. This fish is the largest Goodeid and is also known as the Blackfin Goodea. Its common name originates from the black anal, caudal, dorsal, and pelvic fins found in females. This family contains 49 members that have been placed in 18 genera.

The Blackfin Splitfins have overall rectangular bodies that taper anteriorly to a pointed snout and posteriorly to a rectangular caudal peduncle. They have three distinct colorations: uniform silver without black fins; males being greenish-yellow overall with bluish-green flanks and yellow fins and females having yellow bellies and black anal, caudal, and dorsal fins; and both sexes having a strong dark lateral band with black anal, caudal, and dorsal fins. All three color variants can be found in the same location. They also vary in body shape from long and slender to short and deep-bodied. Their head has a small terminal mouth that projects upward and is equipped with two rows of bicuspid teeth followed by a set of unicuspid teeth. They have a short pointed snout and mid-sized eyes set in the mid to upper part of their head. Their anal and dorsal fins are set well back on the body. Their caudal fin is square.

The Blackfin Splitfins are found demersal at depths up to 5 feet in clear, turbid, and muddy slow-moving freshwater bodies including lakes, ponds, streams, springs, and outflows over clay, gravel, mud, rocks, sand, and silt substrates that are lightly vegetated and have water temperatures between 18oC (64oF) and 24oC (75oF). This species has the highest tolerance of any of the Goodeids for habitat degradation and the greatest distribution. They have been reported to reach a maximum length of 20.0 cm (7.9 inches) with males being slightly larger than females. They are found either mid-water or in aggregations just off the bottom. They are herbivores and consume primarily vegetable materials including green algae, water plants, microcrustaceans, and mollusks. Reproduction is viviparous and involves internal fertilization followed by a short gestation period. Each female gives birth to as many as 167 live young annually.

In Mexican waters the Blackfin Splitfins have a limited distribution and are found in the freshwater systems within the Mexican Plateau in west-central Mexico, such as in the Lerma and Ayuquila rivers in the states of Guanajuato, Jalisco, Nayarit, and Michoacán, which are part of the Pacific drainage, and in the State of Durango where they have been introduced.

The Blackfin Splitfin is straightforward to identify and cannot be easily confused with any other species.

The Blackfin Splitfins are a popular fish with freshwater aquarists. They are used for human consumption on a limited basis. From a conservation perspective they are currently considered of Least Concern with stable but recently declining populations, however, they have not been regularly monitored and there is a lack of historical site-specific population data. The water habitat in some parts of their range has experienced a staggering amount of degradation during the 20th century.

Blackfin Splitfin, Goodea atripinnis, FemaleFish caught in the Luz Springs, La Presa de Verduzco, within the Mexican Plateau of west-central Mexico, Michoacán, February 2017. Length: 7.8 cm (3.1 inches). Catch, photo, and identification courtesy of Ben Cantrell, Peoria, IL.

Blackfin Splitfin, Goodea atripinnis, FemaleFish caught in the Luz Springs, La Presa de Verduzco, within the Mexican Plateau of west-central Mexico, Michoacán, February 2017. Length: 8.5 cm (3.3 inches). Catch, photo, and identification courtesy of Ben Cantrell, Peoria, IL.

Blackfin Splitfin, Goodea atripinnis, FemaleFish caught in the Luz Springs, La Presa de Verduzco, within the Mexican Plateau of west-central Mexico, Michoacán, February 2017. Length: 14.5 cm (5.7 inches). Catch, photo, and identification courtesy of Ben Cantrell, Peoria, IL.

Blackfin Splitfin, Goodea atripinnis, Male.  Fish caught in the Luz Springs, La Presa de Verduzco, within the Mexican Plateau of west-central MexicoMichoacán, February 2017. Length: 15.5 cm (6.1 inches). Catch, photo, and identification courtesy of Ben Cantrell, Peoria, IL.

Blackfin Splitfin, Goodea atripinnis, Male.  Fish caught in a small lake within the Mexican Plateau in west-central Mexico, Michoacán, February 2017. Length: 10.4 cm (4.1 inches). Catch, photo, and identification courtesy of Ryan Crutchfield, Tampa, FL.