Jack Dempsey, Rocio octofasciata

Jack Dempsey, Rocio octofasciata. Fish caught from the Cabbage Slough, Tampa, Florida, September 2015. Length: 8.1 cm (3.2 inches). Catch, photograph and identification courtesy of Ryan Crutchfield, Tampa, Florida.

Jack Dempsey, Rocio octofasciata. Fish caught from Meadow Hotspring, Fillmore, Utah, June 2019. Length: 8.2 cm (3.2 inches). Catch courtesy of Brayden Moore, Peroria, Arizona. Photo and identification courtesy of Chris Moore, Peoria, Arizona.

Jack Dempsey, Rocio octofasciata. Fish caught from the Cabbage Slough, Tampa, Florida, September 2015. Length: 12 cm (4.7 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

Jack Dempsey, Rocio octofasciata. Fish caught from the freshwater drainage canals in the greater Tampa area, Tampa, Florida, May 2018. Length: 14.2 cm (5.6 inches). Catch, photograph and identification courtesy of Ben Cantrell, San Diego, California.

Jack Dempsey, Rocio octofasciata. Underwater photograph taken in Cenote Azul, Quintana Roo, December 2020. Photograph courtesy of Bob Hillis, Ivins, Utah. Identification courtesy of Dr. John Lyons, Madison, Wisconsin.

Jack Dempsey, Rocio octofasciata. Underwater photographs taken within the within the Sian Ka’an Biosphere Reserve, Quintana Roo, March 2021. Photographs courtesy of Marina Sutormina, Stockholm, Sweden. First Photograph and identification courtesy of Dr. John Lyons, Madison, Wisconsin.

Jack Dempsey, Rocio octofasciata, is a member of the Cichlid and Tilapia or Cichlidae Family, and is known in Mexico as mojarra catarrica. Globally, there are four species in the genus Rocio, and three are found in the freshwater systems of Mexico.  Its common name refers to its aggressive nature and strong facial features that resemble the famous 1920s boxer Jack Dempsey.

Jack Dempsey has a “bluegill” oval body profile and are dark purple gray with a very bright, iridescent blue-green color with gold flecks. They have 8 to 11 faint gray-black stripes on their sides. Part of the head and abdomen are a whitish gray. Their dorsal fin has a red margin and there are two gray-black line between the eyes. The juveniles are light ray or tan with faint turquoise spots. Breeding fish are a dark black in color. Their anal fins are long with pointed tips with 8 or 9 spines and 7 or 9 rays; their dorsal fin is long with a pointed tip with 17 to 19 spines and 8 to 10 rays; and the pectoral fins are long extending past the anal fin origin. The fins in the males are longer than those in the female. The lower jaw extends beyond the upper jaw. They have 9 to 12 gill rakers on the first arch.

Jack Dempsey is a freshwater fish that is non-migratory and found in slow moving waters that include canals, lakes, rivers, springs and swamps preferring clear or turbid water over mud, sand, swamp habitat with temperatures between (20^oC/72^oF to 30^oC/86^oF). They have a low metabolic rate and are able to survive in waters that have salinities of up to 8 ppt and hypoxia (low oxygen levels) and can absorb air directly off the surface with large gills relative to their body size. They cannot survive in waters with temperatures of less than 8^oC (46^oF). They are fast growing and reach a maximum length of 25 cm (9.8 inches) with males being larger than females. The Jack Dempsey is active diurnally as an omnivore that consumes algae, crustaceans, fish, insects, mollusks, and worms. They are known to practice cannibalism for their young when ample food is not available. During breeding season the males become highly aggressive. The females lay from 500 to 800 eggs that attached themselves to flat hard surface within logs and rocks. The eggs will hatch within 3 days. The females guard the eggs until they hatch and the males guard the young until they become free swimming. They reach sexual maturity in 1 year with each female will lay several batches of eggs each year. They have life spans of between 3 and 4 years In the wild and up to 15 years in captivity.

The Jack Dempsey is a resident of Mexico’s freshwater systems but has a limited distribution being found in northeastern Mexico from the Verde River basin to the upper Rio Soto la Marina in the States of Coahuila, Nuevo León, and Tamaulipas. They been introduced widely outside their native range.

The Rio Grande Cichlid is very similar to several Black Bases, Sunfishes and Tilapia but differ in that unlike tilapia and most sunfishes, which typically have 3 spines on the anal fin, Rio Grande Cichlids have 7 to 9. The pronounced “hump” found on the head of adult males is not present in Tilapia. They also have a single nostril opening on each side of the head and a broken two-part lateral line not found in Sunfishes and Tilapia.

From a conservation perspective the Jack Dempsey is currently considered to be of Least Concern with stable, widely distributed populations. They are considered to be highly invasive species that compete for food, space and spawning habitat. They are a popular aquarium fish due to its striking colors, that vary from individual to individual and include electric blue, gold and pink, and aggressive personality. Most aquarium fish are raised in captivity. They will quickly outgrow their space and will also consume smaller tankmates. They have also been utilized as a biological research model of behavior.