Pseudobarbus swartzi, Chakona, Albert & Skelton, Paul H., 2017

Chakona, Albert & Skelton, Paul H., 2017, A review of the Pseudobarbusafer (Peters, 1864) species complex (Teleostei, Cyprinidae) in the eastern Cape Fold Ecoregion of South Africa, ZooKeys 657, pp. 109-140 : 123-125

Pseudobarbus swartzi sp. n. Figures 5c, 6d

Proposed common name.

Gamtoos redfin.

Holotype.

SAIAB 203792 (Field no: AC15AL39), male, 80.9 mm SL, Tributary of the Wabooms, Gamtoos River system, - 33.8639772 S, 23.8263333E, collected by A Chakona, B Motshegoa, N Mazungula, W Kadye and R Smith, 21 January 2015.

Paratypes.

SAIAB 203793 (Field no: AC15AL39), 9 unsexed, 35.4-76.0 mm SL, same locality information and collectors as holotype; MRAC 2016-032-P-0001-0004 (Field no: AC16AL02), 4 unsexed, 50.2-61.4 mm SL, main tributary of the Louterwater River, - 33.8333611S, 23.6373056E, Gamtoos River system, collected by A Chakona, S Reddy and R Smith, 18 January 2016.

Etymology.

The species is named after Dr Ernst R. Swartz for his contribution to the biogeography and systematics of Pseudobarbus and the role that he played in mentoring students working on the systematics and biogeography of southern African freshwater fishes.

Diagnosis.

Possession of a single pair of oral barbels separates Pseudobarbus swartzi sp. n. from Pseudobarbus burchelli , Pseudobarbus burgi , Pseudobarbus skeltoni and Pseudobarbus verloreni all with two pairs. It differs from Pseudobarbus quathlambae by having larger scales and fewer scale rows along the lateral line ( Pseudobarbus swartzi : 35-37, mode 35-36 lateral line scales; Pseudobarbus quathlambae :> 65 scales along lateral line). Pseudobarbus swartzi and Pseudobarbus senticeps show some overlap in barbel length (Figure 4), but are clearly separated by scale size (Figure 4). Pseudobarbus swartzi has a higher number of scale rows along the lateral line (34-37, mode 36) vs (25-33, mode 29), and around the caudal peduncle (13-17, mode 16) vs (10-12, mode 11) in Pseudobarbus senticeps . Pseudobarbus swartzi further differs from Pseudobarbus senticeps by lacking a conspicuous lateral stripe which terminates in a triangular blotch at the base of the caudal fin. While there is some overlap in scale counts between Pseudobarbus swartzi and Pseudobarbus afer , it is uncommon (see above). Pseudobarbus swartzi has a higher number of lateral scale series (34-37, mode 36) than Pseudobarbus afer s.s which has fewer lateral scale series (29-35, mode 32). The two species further differ in scale pigmentation pattern (see Figure 6a, 6). Pseudobarbus afer has a band of pigment along the centre of the scales, leaving a clear band along the distal edges of the scale, and producing a distinct mesh or net-like pattern which is more conspicuous on the latero-ventral scales. This pattern is not evident in Pseudobarbus swartzi . Pseudobarbus swartzi sp. n. differs from Pseudobarbus asper by possession of fewer larger scales (lateral line scale series 34-37, mode 36 vs 35-45, mode 37-40; caudal peduncle scale rows 13-17, mode 16 vs 16-22, mode 18-20). Lack of prominent black spots and blotches on the body distinguishes Pseudobarbus swartzi from Pseudobarbus phlegethon .

Description.

General appearance and colouration is shown in Figs 5c, 6d. Morphometric and meristic data summarised in Table 4 are based on 64 specimens (43.6 - 81.1 mm SL) collected from 11 localities across the Gamtoos River system. A fusiform minnow with body slightly compressed laterally. Predorsal profile convex, post dorsal profile straight and descending from origin of dorsal fin to caudal fin insertion. Ventral profile more or less straight from tip of snout to pelvic fin origin. Head relatively short, length almost equal to body depth, its dorsal profile distinctly convex, particularly from its tip to interorbital area. Mouth subterminal, its corner not reaching vertical through anterior margin of eye. Barbels attached from behind the rictus of the mouth, barbel length variable, with some individuals having long barbels reaching or surpassing vertical through posterior edge of the eye, while other individuals have much shorter barbels (see Figure 4c). The eye is located closer to the tip of the snout than to posterior edge of the operculum, eye diameter shorter than snout length. Snout blunt and moderately rounded.

Tuberculation . Mature breeding males develop large conical tubercles on the snout and along the dorsal edge of the nares and eyes. Bilateral clusters on snout include 2-4 tubercles in mature ripe males. Smaller, scattered tubercles develop on the head dorsum. Bands of fine tubercles along dorsal surface of pectoral fin rays.

Scales. Scale rows along lateral line 34-37 (mode 36) ending at hypural, with 1-2 more scales to base of caudal fin; 6-7 (mode 6) scale rows between lateral line and dorsal fin origin; 4-5 (mode 5) rows between lateral line and pelvic fin origin, 5 rows between lateral line and anal fin origin, 16-20 (mode 17-18) pre-dorsal scale rows, 13-17 (mode 16) scale rows around caudal peduncle. Triangular naked patch between the gill covers and anterior base of pectoral fins, scales between pectoral fin origin and pelvic fin origin reduced and embedded. Axillary scales of pelvic fin not prominent or elongate. Scales between posterior edge of head and dorsal fin origin embedded and smaller than flank scales.

Fins. Dorsal fin is inserted about mid-body (excluding caudal fin), origin slightly behind vertical through origin of pelvic fin, with 3-4 unbranched rays and 7 branched rays, distal margin straight to slightly, posterior tip of depressed dorsal fin does not reach vertical through posterior base of anal fin. Pectoral fins fan-shaped, larger in males than females, with 14-16 rays, tip of depressed pectoral fin almost overlapping with pelvic fin in large males, reaches 2 scales to base of pelvic fin in females. Pelvic fin with 8 rays, origin slightly in front of dorsal fin origin, tip of depressed pelvic fin not reaching anterior origin of anal fin, except in mature males. Anal fin with 3 simple rays and 5 branched rays, distal margin straight to slightly convex, origin closer to anterior base of pelvic fin than caudal fin base. In mature males, tip of depressed pelvic fin often surpass point of anal fin origin while they only reach up to the anus in females. Caudal fin is forked, with 10+9 principal rays.

Colouration (live and fresh specimens). Refer to Figure 5c for general live colouration. Body golden-tan laterally, becoming darker dorsally, and lighter to white ventrally. Base of fins bright red, operculum metallic gold.

Colouration (preserved). Alcohol preserved specimens are dark greyish above the lateral line, light grey or whitish below the lateral line and ventrally, breast of freshly preserved specimens silvery (Figure 6). Mid lateral stripe present but comparatively obscure, black blotch at the base of caudal fin inconspicuous.

Osteology. Total vertebrae including Weberian apparatus 37-38 (mode 37), predorsal vertebrae including Weberian apparatus 12-13 (mode 13), precaudal vertebrae including Weberian apparatus 19-20 (mode 20), caudal vertebrae including Weberian apparatus 17-18 (mode 18).

Distribution.

Pseudobarbus swartzi sp. n. occurs in the Kougaberg, Baviaanskloofberg and Elandsberg tributaries of the Kouga and Groot sub-catchments of the Gamtoos River system, and the Kabeljous and Swart River systems which discharge into St Francis Bay (Figure 7). Remnant populations in the Kouga and Groot sub-catchments are highly fragmented due to invasion of the main stem sections of the rivers by alien predators in particular the African sharptooth catfish ( Clarias gariepinus ) and the North American black bass species ( Micropterus spp.). The status and distribution of Pseudobarbus swartzi populations in the Kabeljous and Swart river systems need to be assessed through fine scale geographic surveys. There is also need for investigations to determine the taxonomic status of redfins in the Seekoei and Maitland, two river systems which also discharge into St Francis Bay (Figure 7).

Habitat.

Pseudobarbus swartzi inhabits perennial mountain streams with clear or peat stained water as well as cobble, pebbles and boulders.

Conservation status.

Remnant populations of the species are under severe threat from multiple human impacts including habitat degradation, complete water abstraction and potential invasion by alien fish predators and competitors that are now dominant in mainstem sections of the rivers ( Ellender et al. 2011, 2015). Pseudobarbus swartzi sp. n. (referred to as Pseudobarbus sp. " afer Gamtoos" by Tweddle et al. 2009) was listed as Endangered following the IUCN assessment of the status and distribution of freshwater fishes in southern Africa ( Tweddle et al. 2009). Invasive alien fishes were identified as the single most important threat to this species.