Bluebarred pygmy sunfish  (Elassoma okatie)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The bluebarred pygmy sunfish is a striking fish, despite its small size, and is named after the male’s eye-catching iridescent blue stripes (2). Both the male and female bluebarred pygmy sunfish have conspicuous dark, vertical bands along the body (2), but while the males are coloureda brilliant iridescent blue between the bands, the females are a much more drab beige (3). The rest of the body is blue-grey to black in males, depending on reproductive activity, and pinkish-brown in females (3). In addition to having a slightly longer body, the male also has longer pelvic, pectoral and dorsal fins than the female (2).

Species in the genus Elassoma are known as pygmy sunfishes because they were originally thought to belong in the same family as other sunfishes, the Centrarchidae (4). However, they are now considered sufficiently distinct to be classified in their own separate family, the Elassomatidae, and some claim they are not closely related to other sunfish at all (5). The family and generic name derives from the Greek words ‘elasson’, meaning ‘smaller’, and ‘soma’, meaning ‘body’ (6). The specific name of the bluebarred pygmy sunfish derives phonetically from the local Indian words ‘oka’, meaning ‘water’, and ‘ateeh’, meaning ‘coming from’ (2).

The bluebarred pygmy sunfish has been found at only four sites, all in the south-eastern United States: the Lower Edisto, New and Savannah River drainages in South Carolina (2), and Fort Gordon in Georgia (3).

The bluebarred pygmy sunfish is most commonly found in shallow, slow-flowing water with dense aquatic vegetation and a soft substrate rich in decaying organic matter (2). Typical habitats include roadside ditches and ponds (2).  Despite its limited range, this species can tolerate a range of water temperatures (10 to 32 ºC) and acidities (pH 4.5 to 7.5) (2).

Relatively little is known about the biology of the bluebarred pygmy sunfish. Spawning occurs from late February to March (3), and most individuals do not live longer than one year (3). The diet of pygmy sunfishes typically consists exclusively of larger-bodied invertebrates (5).

Pygmy sunfishes display intriguing and relatively complex reproductive behaviour (7). Reproductive males aggressively defend a territory using what has been termed the ‘sidling threat’ display. The defending male swims close to the intruder, rapidly beating his caudal and pectoral fins while intensifying in colour, and if necessary will strike rapidly at the intruder. The even more bizarre ‘wiggle waggle’ display is performed by the reproductive male to entice a mate. On approach of a reproductive female, the male swims in an undulating path towards the potential spawning area, fluttering the dorsal and anal fins and alternately extending the pelvic fins. If the male is successful in attracting the female, the female will position herself amongst the vegetation, where the male aligns himself at her side and the eggs and sperm are released; the resulting fertilised eggs stick to the vegetation in small clusters. After spawning, the protective male chases the female away from the eggs, leaving the male responsible for defending the vulnerable brood until hatching, which occurs after several days (7).

The close proximity of the majority of known populations to roads makes the bluebarred pygmy sunfish particularly vulnerable to human-caused disturbance and pollution (2). Populations near industries such as paper mills and concrete factories are particularly vulnerable to pollution and sedimentation, which may have been responsible for local extinctions in the past (3). Drought is also likely to pose a significant risk, given that populations predominantly occur in shallow, isolated water bodies (8).

The bluebarred pygmy sunfish is considered a species of ‘Special Concern’ in South Carolina, while in Georgia it is listed as ‘Critically Imperiled’ (3). A species management plan has been proposed for the population in Georgia (3), and many of the South Carolina populations lie within the boundaries of private hunting clubs, where they benefit from indirect protection from development (3). A breeding programme for this species is currently underway at Riverbanks Zoo and Aquarium in South Carolina (8).

View information on this species at the UNEP World Conservation Monitoring Centre.