Blackfin Splitfin, Goodea atripinnis
Blackfin Splitfin, Goodea atripinnis, Female. Fish 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, photograph, and identification courtesy of Ben Cantrell, Peoria, Illinois.
Blackfin Splitfin, Goodea atripinnis, Female. Fish 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, photograph, and identification courtesy of Ben Cantrell, Peoria, Illinois.
Blackfin Splitfin, Goodea atripinnis, Female. Fish 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, photograph, and identification courtesy of Ben Cantrell, Peoria, Illinois.
Blackfin Splitfin, Goodea atripinnis, Male. Fish caught in the Luz Springs, La Presa de Verduzco, within the Mexican Plateau of west-central Mexico, Michoacán, February 2017. Length: 15.5 cm (6.1 inches). Catch, photograph, and identification courtesy of Ben Cantrell, Peoria, Illinois.
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, photograph, and identification courtesy of Ryan Crutchfield, Tampa, Florida.
The Blackfin Splitfin, Goodea atripinnis, is a member of the Splitfin or Goodeidae Family, that is also known as the Blackfin Goodea and in Mexico as tiro. Globally, there are three species in the genus Goodea, and all three are found in Mexico’s freshwater systems. This fish is the largest Goodeid. Its common name originates from the black anal, caudal, dorsal, and pelvic fins found in females.
The Blackfin Splitfin has an overall rectangular shaped body that tapers anteriorly to a pointed snout and posteriorly to a rectangular caudal peduncle. They have 3 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 approximately 40 teeth set in 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 fin has 13 to 16 rays and is set well back on the body; their caudal fin is weakly rounded; their dorsal fin has 12 to 15 rays and rounded and elongated and is slightly behind the anal fin; their pectoral fins have 14 to 16 rays; and, their pelvic fins have 6 rays. They have 39 to 45 long gill rakers on the first arch.
The Blackfin Splitfin is a demersal species that is found at depths up to 2 m (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 of 20.0 cm (7.9 inches) in length 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 one hundred sixty-seven live young in annual cycles. The Blackfin Splitfin 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 Blackfin Splitfin is a resident if Mexico’s freshwater systems but has a limited distribution being found within the Mexican Plateau in west-central Mexico 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, also a part of the Pacific drainage, where they have been introduced.
The Blackfin Splitfin is straightforward to identify and cannot be easily confused with any other species.
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. They are a popular fish with with freshwater aquarium trade. They are used for human consumption on a limited basis.